TAKING GOOD CARE OF YOUR SKIN - eliasandwilliams.com

TAKING GOOD CARE OF YOUR SKINPeter M. Elias, M.D. and Mary L. Williams, M.D.

The Inside-Out of Skin

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| Peter M. Elias, M.D. and Mary L. Williams, M.D. Taking Good Care of Your Skin

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TAKING GOOD CARE OF YOUR SKIN

Skin is the organ that defines our surface. It covers and protects us. It repairs itself when we cut or abrade it. It alerts us to danger when we come into contact with ma-terials that are too hot or too cold or too sharp. It holds a teeming world of micro-bial, want-to-be, invaders at bay – those bacteria and fungi that populate the world around us. Skin asks little of us – just some considerate care. We can be better stew-ards of this precious resource we have been granted, if we understand some basic principles of the skin’s structure and function.

About Our Skin

Back to BasicsThe outer surface of skin – that which we see and touch – is called the stratum corneum. We will return to a more detailed discussion of the stratum corneum after we provide an overview of the structure of skin. We will need to spend more time with this outer layer, because much of what we do to our skin – when we bathe, or apply lotions and creams, or rub and scratch - we do to the stratum corneum. But for now, as we are gaining an overview of the skin, let us simply say that the stratum corneum, which is composed of layers of flattened, ‘dead’ cells, is the outermost part of the epidermis.

Now, here is a paradox: While the stratum corneum is made up of layers of dead cells, it is the business end of the skin.





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The epidermis is a multilayered structure. The innermost layer is called the basal cell layer. This layer is where the cells that continuously regenerate the epidermis reside. These are the mother cells that divide periodically into two. The mother cell stays behind in the basal cell layer– to reproduce again and again.

The other cell, her daughter, slowly moves outward towards the skin surface. As this daughter cell continues on her journey, she changes or matures. Biologists call this maturational process, ‘differentiation’. It involves the manufacture of the proteins and ‘lipids’ (fats) that she will use to form the stratum corneum.

In the final stages of differentiation, the outermost cell dissolves her nucleus and the other cellular structures that were involved in the generation of new molecules. She becomes a fully mature cell of the stratum corneum, a ‘corneocyte’ – a ‘dead’ cell.

Now here is a paradox: While the stratum corneum is made up of layers of dead cells, it is the business end of the skin. This is where the action is taking place – at least in terms of the interface between the self and the outside world. In a sense, the living parts of the epidermis are there merely to serve the stratum corneum – to repair its damage when called upon and to replace spent and discarded cells with a fresh contingent of corneocytes.

Illustrated by Jessica Kraft





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The epidermis in turn is served by the underlying dermis. The dermis is a larger, inner layer of the skin, which provides physical support to the skin through its col-lagen and elastic fibers. These fibers make up the bulk of the dermis. But the dermal layer also holds the blood vessels that deliver nutrients to the epidermis and remove its wastes. It also contains the nerve fibers that transmit signals between the skin surface and the brain.

Other structures that are offshoots from the epidermis – the hair follicles that pro-duce our hairs, the sebaceous glands that produce an oily film called ‘sebum’, and the sweat glands – reside in the dermis as well. We will return to these structures in a little more detail when we discuss some of the skin care issues surrounding them.

Finally, lying below the dermis is an expandable layer of fat (‘adipose tissue’), our energy storage depot.

It is our skin’s job to waterproof us, and that task is given over to the stratum corneum.






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A Closer Look at the SurfaceThe stratum corneum – our outermost skin layer – is that part of the skin that is always at work to keep the outside out and the inside in. The stratum corneum pro-vides our barrier to the world. (Read more about What Is the Skin Barrier and Why Does it Matter?) Readers of this blog will know that this function of skin - the pro-vision of a permeability barrier to conserve our body water - is its most important task, because this is what allows us to live on land.

We, like other living beings, are mostly made up of water. Water is ~80% of our being! Yet, we live surrounded by a much drier atmosphere. It is our skin’s job to waterproof us, and that task is given over to the stratum corneum.

For our purposes here, it is critical to understand that it is the fats (or ‘lipids’) in our stratum corneum that are the main players in the permeability barrier. The epider-mal cells generate these lipids as they mature (or differentiate). As the cells of the

...this is our skin’s ingenious waterproofing system. The lipids repel water...




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epidermis transition into the stratum corneum, they not only give up their nuclei and other or-ganelles, they also deposit (‘secrete’) their lipids outside the cells.

The lipids then organize themselves into mem-brane structures – that envelope the corneocytes. Several layers of membranes surround each cor-neocyte and multiple layers of corneocytes make up the stratum corneum: this is our skin’s inge-nious waterproofing system. The lipids repel water – holding our body water in – and the multiple layers of cells with their lipid coats, provide an insurance policy for the barrier.

Self-renewal is another ingenious feature of our skin. The outermost cells of the stratum corneum have very weak attachments to one another. The friction of daily life – aided by our bathing prac-tices – causes these loosely adherent cells to de-tach from one another and be shed – one by one and invisibly. (For what happens when this nor-mal process goes awry, see our article: Scaly Skin and Ichthyosis: (Nothing to do with fish)).

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What Happens When We Bathe?Bathing is our way of helping the epidermis achieve its self-renewal, by sweeping away the outermost, spent corneocytes along with surface debris – the dirt and bac-teria and other microbes that feed on the debris, the sebum, and the salts left behind from evaporated sweat.

But some bathing practices can do more than just remove unwanted debris. Solvents and detergents can strip the underlying layers of corneocytes of their lipid coats. In extracting the natural oils from the skin, they can damage the skin barrier. When the

...this is our skin’s ingenious waterproofing system. The lipids repel water...

integrity of the barrier is compromised, the skin becomes leaky. Body water can leak out and other molecules – toxins, allergens and pathogenic microorganisms – can make their way in.





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Our ingenious stratum corneum – this very active but ‘dead’ tissue - then notifies the underlying epidermal cells that its barrier has been compromised. A series of re-pair responses ensue, that will ultimately restore barrier function. The timetable for this epidermal repair sequence can be as short as a few hours to as long as several days, depending upon the extent of the original damage to the barrier.

Skin Care: Best PracticesIt follows from the above, that the ideal bathing practice will remove surface debris without, or with only minimal, disruption of the permeability barrier. It also follows that the key descriptor of such practices would be ‘gentle’. Harsh soaps and strong detergents are to be avoided. Overly vigorous or abrasive scrubbing is also not advis-able – except perhaps in some special circumstances.

....the key descriptor of such practices would be ‘gentle’. Harsh soaps and strong detergents are to be avoided.

The ideal cleanser will also not disrupt the skin’s ‘acid mantle’. The skin surface is normally quite acidic. Whereas the interior of the body is maintained at a nearly neutral pH (~7.4), the pH at the skin surface is nearly 2 full logs more acidic (~pH 5 ± 0.5)1.

This acidity has several important functions. First and perhaps most critical, an acid surface discourages the growth of pathogenic microorganisms. In addition, the acid pH of the skin is also critical for the action of a number of enzymes involved in forming the stratum corneum. Enzymes involved in the generation of the lipid types that make up the membranes around the corneocytes are pH dependent (mean-ing that they operate best at certain pH concentrations), as are the enzymes that are involved in dissolving the protein attachments (the ‘proteases’) between the corneo-





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cytes. Loss of skin acidity can result in over-activity of these proteases, which can further damage the skin barrier.

It is safe to say that all soaps and detergents disrupt the acid mantle to some ex-tent. Soaps, which are by their very nature alkaline, tend to do more damage than synthetic detergents, or ‘syndets’, do. But having stated this general principle, it is difficult for the consumer – or for your doctor, for that matter – to know what the pH of a soap or cleanser is. Much of the information is proprietary and not readily

In general, the more acidic products were the least irritating and, in general, these were syndets rather than soaps.

available to the public. Only a few published studies exist to guide our practices, and those few that do, survey only a handful of the myriad of available products.

The information summarized in the following table (Table 1) derives from studies of products available in Mexico and Thailand where they were performed. One of the studies looked at how irritating to the skin the various soaps and cleansers were. In general, the more acidic products were the least irritating and, in general, these were syndets rather than soaps. Many of the products studied are not sold within the US except through Internet venders. And those that seem to be comparable may not have the same composition and pH.





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Table 1: pH of Some Soaps and CleansersIrritation: Low – index ≤2; Moderate = index 2-4; High = index ≥4

Soap or Cleanser ReportedAcidic (pH ≤ 6.0)Physiogel (Steifel)2

Eucerin pH5 Wash Lotion2

Hibiscrub2

Dove ‘Liquid’ Body Wash1

Neutral (pH 6-8)A-Derma Dermopan1

Cetaphil Cleansing Lotion2

Dove White Beauty Bar1,2

Alkaline (pH >8)Nivea Bath Care1

Nivea Bath Care with Almond1

Nivea Bath Care with Oats1

Nivea Baby Creamy1

Johnson’s Baby Soap1

Johnson’s Baby Oat1

Palmolive Green soap1

Palmolive White soap1

Palmolive Botanicals Soap1 Palmolive Botainicals/Camomile1

Camay Classic Soap1

Oilatum Soap1

Zest Aqua Soap1

Comments

Available via internetAvailable via internetAvailable via internetMay be the same as Dove Deep MoistureBody Wash sold in US; Low irritation index

Available via internet; Low irritation indexMay be same as Cetaphil Gentle Skin Cleanser sold in US; Low irritation indexWidely available in US. Low irritation index

All Nivea products tested had a moderate irritation index. Many Nivea products available in the US may or may not be comparable to these.

Widely available in US. Moderate irritation index; May be same as Johnson’s Vanilla Oatmeal Baby Wash. Moderate irritation index

Palmolive soaps are not sold in US except via internet. All have a moderate irritation index.

Moderate irritation indexWidely available in US. High irritation indexWidely available in US. High irritation index

Data adapted from:1) Barada L, Gonzalex-Amaro R, Torres-Avarez et al. Correlation between pH andirritant effect of cleansers marketed for dry skin. Int J. of Dermatol. 41:494-499,2002.2) Boonchai W and Iamtharachai P. The pH of commonly available soaps, liquidcleansers, detergents and alcohol gels. Dermatitis 3: 154-156, 2010.





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It seems odd that in an age of near miraculous biomedical scientific discoveries, of designer drugs and of the genetic revolution, and yet we don’t know the pH of skin cleansers, nor how these products affect our skin barrier. Because of the limited information available, we can offer little more than the most general advice: use a ‘gentle’ cleanser, and use it with ‘moderation’.

Some Like It HotThe duration of the bath and the temperature of the water also make a difference. Just as we tend to use hot water and plenty of dish soap when we clean a dirty fry-ing pan, we also use warm water to increase the efficacy of our personal cleansing practices. Warm temperatures fluidize lipids – shifting them from a more solid to a more mobile, fluid state. This helps to mobilize and remove surface debris, but warm waters also fluidize the lipids in our membranes surrounding the corneo-cytes, rendering them, too, more easily extracted by soaps and detergents.

...but warm waters also fluidize the lipids in our membranes surrounding the corneocytes, rendering them, too, more easily extracted by soaps and detergents.

Maybe we have come to love the sensuality of a long soak in a tub of hot water – the water as warm as we can take it – and maybe we like to toss in some bubble bath, to increase the sheer luxury of this suspension of time or to envelope our emerging limbs in suds.

But consider what is happening in our stratum corneum. The warm water is flu-idizing the membranes; the detergents that generated the suds are dissolving and extracting these fluidized lipids. Water from the bath is leaking into the corneocytes (because the corneocytes possess small, osmotically active molecules that attract





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and bind water). Finally, we emerge from our bath, flushed from the heat and re-laxed, our skin cells hydrated and plumped up. We towel off. We feel great.

But then, the water begins to evaporate. First, we loose it from the surface, then from those overhydrated corneocytes. Our skin dries out – it soon becomes even drier than it was before our bath! Our body water, too, begins to leak out through our damaged skin barrier. Also, when surrounded by bath water, the water pressure pushed some of our tissue water back into the blood and our kidneys filtered out this excess water from the blood. Now we are suddenly thirsty. Our long bath has resulted in a net loss of water - from our outer skin cells and from our bodies!

We can replace our body fluids by drinking. Our skin will need time to repair itself. But ultimately our corneocytes will rehydrate themselves, too. Yet for some people – people with a tendency towards dry skin, like the elderly or like those who have a predisposition to develop eczema (or ‘atopic dermatitis’) – this kind of ‘indulgent’ bathing can tip them over the edge into ‘problem dry skin’.

Yet, we will put almost anything on our skin – with little concern for what it is or what it might actually be doing.

Greasing Up.We humans like to bathe. We also like to put stuff on our skin, because we think it will make us look and feel better. We probably spend a lot of time thinking about what food we will put into our bodies. Nutrition is a major human obsession – as it well should be. And we would usually think twice before squirting any foreign material into our airway. If tobacco and other substances that we inhale against our better judgment didn’t have pleasurable and/or addictive qualities, we wouldn’t con-sider polluting our lungs with their smoke. Yet, we will put almost anything on our skin – with little concern for what it is or what it might actually be doing.





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Cortisones (or ‘glucocorticoids’) are one example of lipids that can penetrate through the stratum corneum to affect deeper regions of the skin – and sometimes even to enter the blood and other parts of the body.

Fortunately, most of the time, what we smear on our skin doesn’t do too much harm. Keep in mind that whatever goes onto our skin surface needs to get past our permeability barrier – a system that was designed by nature to keep things out. And our skin barrier does a very good job of keeping out large complex molecules – like most foreign proteins, for example.

So, for example, if you have been seduced into trying to fix some of your wrinkles by applying a cream that contains ‘collagen’, you have been sold a pipe dream. This protein, collagen, is far too large a molecule to be able to penetrate through the stra-tum corneum’s permeability barrier, then to percolate down past all the epidermal cells and into the dermis where it is supposed to plump up your skin with additional collagen. Frankly, whatever ‘collagen’ is in this product will simply stay on the skin’s surface until it is rubbed off or washed away.

The skin’s barrier also prevents many small, water-soluble molecules from penetrat-ing deeper into the skin. Just as the permeability barrier retards the outward move-

ment of water, so too it holds back the inward penetration of molecules that easily dissolve in water. Salts and sugars would be examples of molecules that the skin’s barrier excludes from entry.

The types of molecules that can more readily pass through the skin are those that are ‘lipophilic’ – meaning that they are lipids themselves. Cortisones (or ‘glucocorti-coids’) are one example of lipids that can penetrate through the stratum corneum to affect deeper regions of the skin – and sometimes even to enter the blood and other parts of the body.





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Most of the creams and ointments that we apply to our skin are lipid-based. So, what happens to them? Fortunately for us, most of the time the answer is once again, ‘Not much’. The vast majority of lipid-based skin products are derivatives of petroleum (petrolatum) or waxes from the wool of sheep (lanolin). These lipids are foreign or ‘non-physiologic’ to our skin and, after they are applied, they tend to remain on or near the surface of the skin.

They can provide a temporary lipid seal to the skin, but ultimately, like collagen and other large foreign molecules, they wear off through friction or with bathing as the outermost corneocytes are shed. Nonetheless, they are very useful in many popular products for skin hydration. For more on these emollients see our article, “When the Skin Barrier Fails: Barrier Repair Therapy”.

As we have seen in the preceding sections – one way to get stuff into our skin is to damage the permeability barrier. Although few potions would advertise this as a benefit, a lot of minor barrier damage occurs all the time with many topical prod-ucts. For example, fatty acids are commonly added to topical products. One such common ingredient is ‘stearic acid’.

Now, one might think that this would be beneficial, because fatty acids are one of the 3 key lipid classes that form the membranes of the stratum corneum (see our ar-ticles: What is a Fatty Acid? and What is the Skin Barrier and Why Does It Matter?). And many fatty acids, including stearic acid, are indeed physiologic to the skin. But physiologic lipids have a different fate from the non-physiologic lipids, petrolatum and lanolin.

Physiologic lipids do not stay on the skin surface, they penetrate through the stra-tum corneum. Then, they are imbibed by the underlying layer of epidermal cells. The cells ‘process’ them and then send them back out into the stratum corneum – in little packages - along with the other lipids these cells are continually in the process of manufacturing. Once secreted, they will form the waterproofing membranes. But they will only form ‘good’ membranes, if the correct ratio of the three key lipid classes (cholesterol, ceramides and free fatty acids) is present. If only one or two of



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the three physiologic lipids is applied – it can ‘upset the balance’ of lipids – and the membranes that are so-formed are faulty. They are leaky. Hence, lotions and creams containing fatty acids or ceramides alone, without the full complement of physiologic lipids, can damage the barrier.

...lotions and creams can have a neutral or alkaline pH, instead of an acidic pH, and thereby damage the barrier, just as alkaline and neutral soaps and cleansers do.

In addition to damage to the barrier from the application of an ‘incomplete lipid mix’, there are other ways damage can occur. For example, lotions and creams can have a neutral or alkaline pH, instead of an acidic pH, and thereby damage the bar-rier, just as alkaline and neutral soaps and cleansers do. And the same difficulty in knowing the pH of a product holds for skin lotions and creams, as it did for soaps and detergents.

Table 2 summarizes some of the available information on the pH of these types of products. In the study summarized here, the water content of the products was also determined. Those that contain more water, contain less lipid. This may make them easy to spread on the skin, but it is likely that their ability to moisturize the skin will be reduced. Those that contain a great deal of water may actually have the net effect of drying of the skin, just as bathing can.

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Table 2: pH and Water Content of Some EmollientsAdapted from Shi, Tran and Lio, 2012.

Acidic (pH ≤ 6.0)

Vanicream® moisturizing skin creamTheraplex® emollient for severely dry skinEpiCeram® emulsionCetaphil® daily advance ultrahyrating lotionEucerin® original dry skin therapy lotionEucerin® intensive repair body creamVanicream® light moisturizing lotionCetaphil® moisturizing creamEucerin® menthol itch relief lotionAveeno® skin relief moisturizing lotionEucerin® calming creamAveeno® skin relief moisturizing lotion with mentholAveeno® positively radiant daily moisturizerCetaphil® restoraderm skin restoring moisturizerDML® Forte body moisturizing creamVaseline® intensive rescue skin protectant body lotionAcid Mantle® creamAquanil® lotionAveeno® daily moisturizing lotionCeraVe® moisturizing lotionCeraVe® moisturizing cream

Neutral (pH >6 to ≤ 8.0)

Triple Paste®Aquaphor® ointmentAveeno® advanced care moisturizing creamDML® moisturizing lotionAquanil® HCDove® day lotionNeosalus® cream

Alkaline (pH > 8)Eucerin® original dry skin therapy creamEucerin® intensive repair body lotion

Water content*

Very LowVery LowVery LowVery LowVery LowVery LowLowLowLowLowLowLowLowLowLowHighHighHighHighHighVery High

Very LowVery LowLowLowHighHighVery High

Very LowHigh





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To Grease or Not to GreaseFortunately for most of us, our skin can repair itself and will quickly restore its bar-rier to normal after the minor damage it receives from our bathing practices. But in some instances, it could use some additional help. For example, as we age, our skin becomes less able to repair itself. We are prone to develop problem dry skin, if our bathing practices are too harsh, or if the humidity where we live is very low – such as in our heated homes during winter months - or if we have inherited a tendency for dry skin (see: About Dry Skin).

Cortisones (or ‘glucocorticoids’) are one example of lipids that can penetrate through the stratum corneum to affect deeper regions of the skin – and sometimes even to enter the blood and other parts of the body.

For those with dry skin or a tendency to develop dry skin, it is particularly impor-tant that bathing practices be gentle: avoid super-hot water, use a mild, low pH cleanser and use it sparingly. And then, seal that rehydrated skin in by applying a good moisturizing cream or ointment to the skin, immediately after briefly towel-ing off. In general, we prefer products in a heavier cream or ointment base to most lotions. Although the latter may be easier to apply, they can, because of their higher water content, have a net drying effect on the skin (See: What is the Best Lotion for My Dry Skin?).



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Special Cases

Facial SkinFacial skin is special - in part because we make it so. It matters the most to us, be-cause our face, more than any other part of our bodies is where we present ourselves to others. It is also special, because it is the most uncovered part of our skin, which makes it most vulnerable to the effects of sunlight, as well as to airborne pollutants, allergens, and other irritants. But facial skin is also special, biologically. It is heav-ily endowed with oil, or ‘sebaceous’, glands. These glands are part of the hair follicle apparatus. They exist everywhere on the body that hair follicles are found – which is almost everywhere. On the face, though, and particularly on the central face, these glands tend to be unusually active and enlarged, while their associated hairs are quite small.

The oily product of these glands, or ‘sebum’, is extruded through the hair follicle opening where it then forms a film over the skin surface. Human sebum is com-





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posed mostly of fatty acids, derived from the breakdown of triglycerides, and a lipid called ‘squalene’ – a molecule that was halted on its way to becoming cholesterol. No one really knows for certain what the good functions of sebum are – although it seems reasonable to assume that if the body has gone to all this metabolic expense and trouble to manufacture the stuff, it must be good for something. It seems likely that sebum helps to hydrate the stratum corneum. It also lubricates hairs, and the fatty acids in it probably help the skin’s antimicrobial defenses.

Sebaceous glands are hormonally driven – by sex hormones, that is. While the glands are small and minimally active in preschool children, they increase in size

Frequent – once or twice a day – washing of the face, using warm water and a gentle cleanser, is reasonable for most adolescents and adults.

and activity as they begin to be stimulated by sex hormones (mostly those hor-mones with ‘androgenic’ activity). Follicular pores, plugged with sebum and other cellular debris, produce small skin colored bumps (closed comedones) or black-heads (open comedones). These early harbingers of acne can develop in children a few years before other signs of puberty, such as breast enlargement or pubic hair, de-velop. (For more on the significance of blackheads and other signs of acne, see: Do Blackheads Mean My Face is Dirty? The quick answer here is, ‘No’.)

People vary – probably genetically – in how active their facial sebaceous glands are. It is possible to have oily facial skin and dry skin elsewhere on the body. This does not seem fair, perhaps, but it is quite common. Frequent – once or twice a day – washing of the face, using warm water and a gentle cleanser, is reasonable for most adolescents and adults. Very active glands can produce a visibly oily sheen to the face. Alcohol or other solvent-based wipes can remove this film, but they will nei-ther halt nor stimulate its rapid replenishment with a fresh slick of sebum within hours.



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HandsHands come in for a lot of insults because they are ‘out there’ – they are our body parts most physically engaged with the surrounding environment. While its impor-tant for our hygiene to wash our hands, too frequent hand washing can become a problem.

Our palms – and soles too – are one of the specialized regions of our skin. They lack hair (and therefore sebaceous glands). Their epidermis and its overlying stratum corneum are much thicker than on the remainder of the body. One would think that the skin barrier would be especially robust on the palms and soles, but in fact, the opposite is true. They have a relatively weak barrier to water loss. This is because, al-though there are many more layers of corneocytes on the palms and soles, the stra-tum corneum there is relatively deficient in the lipid membranes that coat the cells and waterproof the skin. For example, whereas fat or ‘lipid’ makes up about 10% of





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the dry weight of the stratum corneum elsewhere on the body, on palms and soles lipids account for less than 3%. The thickened stratum corneum is therefore not able to provide a super-barrier, even though it is well designed to withstand more fric-tional stress.

It follows, then, that palms and soles are particularly vulnerable to the loss of smaller cohort of skin lipids from overly vigorous bathing practices.

Then, too, consider our contemporary germ phobia – a stance that is not inappropri-ate given all the microbial threats around us. We are encouraged to wash our hands frequently, and at every turn, to pump some germicide onto our hands – products that are often provided in an especially drying, alcoholic gel. Our poor hands are challenged many times each day.

Some people have occupations that take hand washing to an even higher level. Health care workers need to wash with soap and water or with a germicide between each patient contact. Surgeons and their assistants must scrub their hands with a soapy brush for a minimum of 15 minutes before each operation. Dishwashers im-merse their hands repeatedly in hot water and detergents, to name just a few of the occupations as risk for hand dermatitis. Dermatologists have known for years that pediatric patients may ‘outgrow’ the eczema on their arms and legs, but – if they assume one of these occupations – they likely will return as adults with persistent hand eczema.

We can’t forgo hygiene – at least not reasonable hygiene. But we can protect our hands when doing wet work, by wearing protective gloves. We can search for more gentle cleansers and use cooler water. We can use germicides that are not as drying, such as products that also contain skin conditioners. And we can use a good emol-lient after each cleansing (Table 2). If we have hand eczema, a preparation based upon physiologic lipids may be the best choice (See When the Skin Barrier Fails: Barrier Repair Therapy)







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Feet and Body FoldsFeet are a lot like hands, biologically, although in practice we treat them very dif-ferently. Feet often come in for a lot of neglect. Nonetheless, they tend to do quite well, most of the time. One skin condition that they are prone to is ‘intertrigo’. This is a skin condition of toe webs and other body folds can develop when they become overly moist from insufficient exposure to air. The warm and over-hydrated stratum corneum sets the stage for microbes that love to live in the tropics – especially fungi. Yeasts are a form of fungi that are particularly fond of growing in the folds under the arms, under breasts, or under rolls of fat, if we have acquired any. If the weather

Prevention is the key to recurrent infections. Keep the folded areas as dry as you can.

turns warm and we sweat a lot, they love it. Yeasts, too, enjoy the warm and moist environment under diapers. Toe webs and groins are the preferred habitat for an-other family of fungi, the ‘dermatophytes’. These are the agents of athlete’s foot and jock itch.

Treatment of these fungal infections is with the appropriate antifungal agent. Many of these are available over the counter, but because yeasts and dermatophytes have somewhat different sensitivities to these medications, it is best to have your derma-tologist make a specific diagnosis. Also, with severe or very widespread infections, an oral antifungal medication given by prescription, may be needed.

Prevention is the key to recurrent infections. Keep the folded areas as dry as you can. Sandals or other shoes that let the toes ‘breathe’ are a good idea in summer. Wear loose-fitting cotton undergarments Absorbent powders sprinkled into socks can be helpful. (But powders are probably not a good idea for your baby’s diaper rash or body folds, because of the risk of inhalation.)





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HairHair is dead; in the same way the stratum corneum is dead. And, like the stratum corneum, hair is also self-renewing. But it does so a little differently. Rather than flake off cell by cell, the entire hair is periodically shed and a new hair begins to grow from the base of the follicle. Each hair follicle has its own little clock ticking, and each is independently engaged in the growth and shedding cycle. Thus, unlike other species that molt, normally we shed a few hairs each day – up to a hundred or so from our scalp each day. If you have long hair, this normal shedding may be noticeable as piles of hair accumulate in the tub or shower drain.

Also, like the stratum corneum, hair is generally fairly tough. It can tolerate daily washing or shampooing, but these practices can roughen its outer surface (or ‘cu-ticles’) leaving the hair more vulnerable to damage during combing or brushing. A conditioner – applied during or after shampooing – can smooth down the cuticles and make the hair easier to comb.





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In most cases, the choice of shampoo is open to personal preference. But if you have a flaky or itchy scalp, you may benefit from a medicated shampoo. The most com-mon cause of dandruff is ‘seborrheic dermatitis’. This is a skin condition often – but not always – associated with an oily scalp. Shampoos that contain zinc, selenium, or antifungal medications, such as ketoconazole, can be helpful when used 2 to 3 times a week. For most people, this will alleviate their symptoms of itch and excessive flaking of the scalp. A consultation with a dermatologist is recommended if they do not give relief, particularly if the scaling is limited to discrete patches, or if it is ac-companied by visible patches of hair loss or breakage.

Some hair treatments – permanents, bleaches, straightening – are harsher and can damage the hair. With enough accumulated damage, the hair shafts may even break. The only solution here is to wait until new hairs grow out of these follicles to replace the broken, damaged hair. And the timing of this replacement process is up to each follicle’s internal clock. Patience is the word.

With some hair care practices it is possible to damage the hair follicle itself. When the hair follicle is damaged, it may no longer produce hairs. This kind of hair loss or ‘alopecia’ is most often caused by sustained (or chronic) tension or pulling on the hair, as can happen if the hair is braided too tightly, in tight ‘corn rows’, for example. This ‘traction alopecia’ is best treated by prevention – by changing hair care prac-tices to release the tension on the hair, before the hair follicle is permanently dam-aged. At some point, there is no return – and once gone, the hair follicle will not come back.





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Babies’ SkinThe skin of babies is another special case. At birth the stratum corneum quickly ad-justs from its former life in a wet world, to our terrestrial life in a dry world. The skin barrier of the full-term newborn is quite competent – at least when it is not stressed. But the pH of their skin is not as acidic as adult skin, and it takes several weeks for this characteristic to mature. Full term babies can sweat, but they are not efficient in this process. Therefore, they are not fully capable of regulating their internal temper-ature through sweating. One quite operational aspect of newborn skin is their seba-ceous gland activity. This is because these glands have been stimulated during fetal life by maternal hormones. But, as the effects of these hormones recede after birth, the glands slowly become less active, and they enter a dormant state until the child starts down the path to puberty.





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Despite the fact that their skin barrier is quite capable, we are still very conservative in what we apply to babies’ skin. One good reason for this is that they have a large surface area relative to their smaller volume; therefore any chemicals that are ab-sorbed through the skin will achieve a higher concentration in their bodies. Babies, of course, are very different from adults in other ways that have nothing to do with their smaller size. For example, their kidneys and livers also are not fully mature – hence their ability to detoxify and excrete drugs and other foreign molecules is not fully developed.

Fortunately for their skin care needs, babies during their most immature months are quite immobile. Their skin – with the exception of the diaper area - does not be-come as soiled as does the skin of older, more active babies and children. Therefore, full body baths are not needed as often in these young infants. Gentle skin care with

Skin care products are often designated specifically for use on babies. But keep in mind that this may be little more than a marketing tool.

a soft cloth, tepid water and a limited amount of a mild cleanser is all that most of them require. If they have a tendency to develop dry skin or eczema, application of an emollient after bathing will help to restore their skin barrier.

Skin care products are often designated specifically for use on babies. But keep in mind that this may be little more than a marketing tool. Little to no proof is required of the manufacturer that the products are particularly safe or effective for infants. Some parents prefer to only use ‘natural’ products on their children’s skin. But ‘natural’ is also no guarantee of safety. Some of the deadliest chemicals we know are completely ‘natural’ – consider, for example, the venom of poisonous snakes. Soaps, as extracts of animal fat, can be con-sidered ‘natural’, but these are lye extracts. This makes soaps highly alkaline. If





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your infant has sensitive skin – if he or she has a tendency to develop eczema – the harsh, alkaline pH of ‘natural’ soaps may not be the best choice for the baby.

The diaper area does need frequent cleaning – particularly after each bowel move-ment. Feces not only contain the bacteria and yeasts that live in the colon, they also contain the enzymes that breakdown proteins and fats during the digestion of food. These enzymes and their digestion products can be very irritating to the skin. The

If your infant has sensitive skin — if he or she has a tendency to develop eczema — the harsh, alkaline pH of ‘natural’ soaps may not be the best choice for the baby.

skin barrier under the diaper is often compromised further because of the continu-ally moist environment. It is easy to see how a rash can readily develop when bowel movements are not quickly and completely cleaned from the skin. But even the most diligent parents may not be able to prevent a diaper rash from developing if their baby has diarrhea.

If a diaper rash is starting to appear, after cleansing the area with tepid water, a soft cloth, and a gentle cleanser, apply an occlusive ointment – such as petroleum jelly. This will protect the underlying skin from additional fecal contact. But if the rash becomes more severe or prolonged, a secondary infection with yeast could be complicating the problem. Your doctor may recommend the use of an anti-in-flammatory agent, such as a mild cortisone ointment, in conjunction with a topical antifungal medication.





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Sun ProtectionIt probably will not come as news to our readers that exposure to too much sun-light in not good for your skin. The hard part is to define ‘too much’, because that depends on many factors: your natural skin pigmentation, as well as the geographic location of the exposure, the time of year and the time of day. Clearly, we want to avoid those exposures that could result in painful sunburns. But it is also advisable to avoid accumulating exposures that over the years will lead to the development of skin cancer. And, we probably don’t want to develop the wrinkles of photoaging, either. For more about wrinkes and aging, see: Aging Skin: Beyond Wrinkles.

The first positive step in that direction is to avoid sun-bathing and other practices, such as visiting tanning salons, with the goal of darkening the color of our skin.



http://eliasandwilliams.com/aging-skin-beyond-wrinkles/



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Suntans are not an effective form of sun protection in themselves, and their pursuit will certainly add to our long term risk of developing sun-induced skin cancers and wrinkles.

The practice of good sun protection does not mean one has to stay indoors and miss out on all the fun in life. But it does take some effort and diligence. One strategy is to schedule summertime, sun-intense activities like swimming lessons or tennis games to the early morning or late afternoon hours.

Another is to wear sun-protective clothing – hats with a full brim, long sleeves and long pants – during the peak sun hours of the midday. And for areas of the skin that cannot be covered with clothing, one can apply a sunscreen.

...sunscreens should not be our first and only strategy to protect our skin from excessive UV exposure.

But note here the order of priorities for action: First, avoid sun bathing and other intense exposures during the peak sun hours when practical. Second, wear appro-priate protective clothing. The third priority is to use a sunscreen. In other words, sunscreens should not be our first and only strategy to protect our skin from exces-sive UV exposure.

Many sunscreen products are available. The key is to choose an effective one and then to use enough of it and to reapply frequently to achieve good protection. What level of sun protection factor or SPF we choose again depends on many factors – the depth of our natural pigmentation, the geographic location, the time of year and time of day, the duration of the anticipated exposure and the activities we may be engaging in during the exposure.





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In making your choice, it may help to keep in mind a few general principles.

1) If you will be active and sweating, a water-resistant formulation will provide lon-ger coverage. Even if the product is water-resistant or ‘water-proof, you will need to reapply after swimming.

2) Most people do not apply enough of the sunscreen to achieve the sun protection factor (SPF) labeled on the product. Sunscreens with a high SPF, therefore, are likely to give better protection with our usual patterns of application, because they will compensate somewhat for our under usage.

3) Its difficult to achieve complete coverage with spray formulations – skip areas are a common problem.

4) Ideally, your product should protect not only against UVB – the sun-burning and cancer-inducing rays – but also against UVA - because these wavelengths may promote some skin cancers, and they certainly can promote the development of wrinkles.





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Selected References1. Ali M and Yosipovitch G. Skin pH: From basic science to basic skin care. Acta Derm Veneriol 93: 2013 (epub).

2. Barada L, Gonzalez-Amarao R, Torres-Alvarez B et al. Correlation between pH and irritant effect of cleansers marketed for dry skin. Int J Dermatol 41: 494-499, 2002.

3. Boonchai W and Iamtharachai P. The pH of commonly available soaps, liquid cleansers, detergents and alcohol gels. Dermatitis 21: 154-156, 2010.

4. Draelos ZD. Concepts in skin care maintenance. Cutis 76: 19-25, 2005.

5. Elias, PM, Wakefield, JS. Skin barrier function. In: Nutrition for Healthy Skin. Krutmann, J and Humbert, JE (Ed.), Springer-Verlag, Berlin, 35- 48 (2010).

6. Elias, PM. Formation and function of the stratum corneum acid mantle. In: Stra-tum Corneum: the Vital Structure. Marks, R, Matts, P, and Leveque, J (Ed.), The Stratum Corneum Group, Cardiff, 1-4 (2005).

7. Fluhr JW, Darlenski R, Taieb A, et al. Functional skin adaptation in infancy - al-most complete but not fully competent. Exp Dermatol. 2010 Jun;19(6):483-92.

8. McCusker MM, Grant-Kels JM. Healing fats of the skin: the structural and immu-nologic roles of the ω-6 and ω-3 fatty acids. Clinics Dermatol 28: 440-451, 2010.

9. Shi VY, Tran K, Lio PA. A comparison of hysicochemical properites of a selection of modern moisturizers: hydrophilic index and pH. J Drugs Dermatol 11:633-636, 2012.





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About Peter M. Elias, M.D. and Mary L. Williams, M.D.

Peter M. Elias, M.D.

Peter M. Elias, M.D. is a Professor in the Department of Dermatology at the University of California San Francisco, and a Staff Physician at the Veterans Affairs Medical Center, San Francisco. He received his medical degree from the University of California San Francisco and trained in dermatology at Harvard University. Dr. Elias has authored or co-authored over 550 peer-reviewed scientific articles, innumerable review articles, and he has edited or co-au-thored three books on the subject of the skin barrier in health and disease. He is an invited speaker at national and inter-national scientific meetings, is a consul-tant to the pharmaceutical and cosmetic industries, and has received numerous awards for his scientific discoveries in-cluding the William Montagna and the Kligman-Frost Awards from the Society of Investigative Dermatology.

Mary L. Williams, M.D.

Mary L. Williams, M.D. is a Clinical Professor of Dermatology and Pediat-rics at the University of California San Francisco. She received her medical degree from the University of Chicago, trained at the University of California San Francisco, and is board certified in both pediatrics and dermatology. Her laboratory research has focused on the pathogenesis of inherited disorders of cornification (the ‘ichthyosis’) and on the prenatal development of the epi-dermal permeability barrier. She is the author of over 150 peer-reviewed scien-tific publications, and an invited speaker at regional, national and international scientific meetings. She is the recipient of a Distinguished Service Award from the American Academy of Pediatrics. Currently Dr. Elias and Dr. Williams are writing a book on the skin permeability barrier.

To contact Elias and Williams, please click here.



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TAKING GOOD CARE OF YOUR SKIN - eliasandwilliams.com