Sunscreens

SunscreensSunscreens were first developed for soldiers in World War II to absorb “sunburn causing rays”. The red veterinary petrolatum which is working as a physical blocker of ultraviolet radiation. (but it is red and sticky substance).

Exposure to sun light leads to erythema (reddening) which leads to Formation of tan (protective reaction of human body).increase melanin prodection.

The sun emits constant flow of energy in the form of electromagnetic radiation .

 The lower energy radiation takes the form of electric & radio waves with wavelengths up to 105 m . Middle -the optical range = UV (100-400) nm Photo-chemical effect.

- Visible light (400-800)nm (light effect)( - 800-1000)nm is near IR (detected as heat).

Highest energy; its represented by (gamma and cosmic rays).¹ 

The classification of UV radiation according to physiological effects:

1 -UV A range, 320 - 400 nm: . Vitamin D production Which effects direct tanning of the skin without erythema ( sunburn). it causes wrinkles and accelerates aging of the skin.

2-UV B range, 280 - 320 nm: UVB are erythemogenic radiations, produce sun burn irritating reactions and stimulate the formation of melanin which leads to the development of tan.UVB causes cataracts, immune system damage, and skin carcinomas.

3-UV C range, 100 - 280 nm:(germicidal UV) , absorbed by the ozone layer and does not reach the earth.¹

The sun’s light is strongest when it is highest in the sky (normally from 10 AM to 4 PM). UV rays are strongest during the summer. ¹UVA radiation is stronger in the early morning and late afternoon when the sun's rays reach the Earth at an angle².

UVB radiation is stronger between late morning and early afternoon when the sun's rays are directed straight down at the Earth.³

Tanning:Exposure to sun light leads to erythema (reddening) which leads to Formation of tan (protective reaction of human body).increase melanin prodection. ¹

Melanin is synthesized in the melanocytes found in the epidermal basal layer,within the melanocytes melanin is bound to protein matrix to form melanosomes. The melanocytes transfer their melanosomes to surroundingkeratinocytes and migrate upward through the epidermis.⁴Direct effect of UV radiation In UV-induced melanogenesis

1-UVR activate Nitric oxide (NO) syanthase and 2-the resulting NO produced by melanocytes and keratinocytes activates the melanocytic-soluble adenylate cyclase. 3-This leads to higher concentraions in cyclic guanosine monophosphate (cGMP)

4-which in turn stimulate melanogenesis (increase pyrimidine dimers) via the enhancement of tyrosinse expression and activity.⁴

UV-A radiation creates oxidative stress, which in turn oxidises existing melanin and leads to rapid darkening of the melanin. it does not lead to greatly increased production of melanin.⁵

UV-B radiation increases production of melanin (melanogenesis), which is the body's reaction to direct photodamage (formation of pyrimidine dimers) from UV radiation.⁶There are three types of Tanning:

 1 .Immediate tanning: (300 – 660) nm. Involves the immediate darkening of unoxidized melanin granules. It reach maximum after one hour and begins to fade 2—3 hrs after exposure. UV-A

 2 .Delayed tanning:(295-320 )nm. Involves the oxidation of melanin granules present in the basal cell layer of the epidermis and their migration towards the surface of the skin. Starts one hour after the exposure and fades rapidly after 100-200 hr following the

exposure.  3 .True tanning:(295-320 )nm. Starts two days after exposure, it

reaches its maximum about (2-3) weeks later. UV-B¹

Adverse effects of sunlight:-  Short term effect Sunburn:

 Temporary damage of the epidermis.- Symptoms:

slight erythema, painful burns, Blistering followed by peeling, fever, nausea and pruritus.

- A first-degree sunburn reddens the skin .- A second-degree sunburn causes reddening of the skin with

some water blisters¹⁰.- Sunburn of skin is a direct result of:

 1-Denaturing of its protein constituents.2-Histamine like substances released by the damaged cells are

responsible for the dilation of blood vessels and erythema and swelling (edema).

3-Photochemical degradation products which trigger a series of free-radical reactions leading to the formation of the biologically active substances Produce symptoms described.¹

- Chronic Exposure:

Mainly affect (sailors, farmers, and construction workers)This long term effect can cause:

1-The development of skin cancer.

2-Degenerative changes in the connective tissue of the corium, (premature aging of the skin). -loss of natural elasticity.-appearance of’ wrinkles.-thickening of the skin. all resulting from the loss of the skin’s water- binding capacity.(TEWL)

3-Increased tendency to form skin blemishes. 

4-Berlock dermatitis ( irregular discoloration), bergamot and other citrus oils followed by exposure to sunlight (perfume).¹

  

-Beneficial Effects Of Sun light:

1-Psychologically & physiologically in general sense of fitness, peace of mind & general well being.¹

 -Sunlight stimulates the production of Serotonin, a neurotransmitter in the brain that regulates mood. Moderately high serotonin levels result in more positive moods and calm yet focused mental outlook.

-Sunshine decreases the symptoms of depression by releasing endorphins. Endorphins are the body's natural anti-depressants and are very beneficial in cases of seasonal depression.⁷

2-It stimulates blood circulation.¹ Sunshine enhances blood circulation by dilating blood vessels in the skin. This brings more nutrients and oxygen to cells when capillaries are open resulting in a better health.⁷

3-Increases the formation of hemoglobin.¹Sunlight greatly increases the body's consumption of oxygen. Through added numbers of red cells and increase in their hemoglobin, the oxygen carrying power of the blood is increased.⁷

4-Promote reduction in Blood Pressure.¹It makes the heart healthier by lowering the resting pulse rate and decreasing blood pressure⁷.

5-Prevention &treatment of Rickets.¹ Sunlight stimulates the body to create vitamin D. A single sun exposure to the face, neck, arms and legs for 10-15 minutes can produce anywhere from 1000 international units (IU) to 3000 IU of vitamin D depending on your skin type, which is all that is required by your body in a day. This vitamin promotes the absorption of calcium in the gut and transfers calcium across the cell membranes, which provides strength to the bones. Vitamin D can offer protection from some cancers (such as lung, prostate, colon and skin cancer), osteoporosis, rickets and diabetes. It also helps to lower blood cholesterol levels thus helping to fight heart disease.⁷

6-Treatment of Psoriasis.¹The mechanism of action probably involves activation of psoralen by UVA light which inhibits the abnormally rapid production of the cells in psoriatic skin. There are multiple mechanisms of action associated with PUVA, including effects on the skin immune system (reduces the number of dendritic cells).⁸

7-Formation of the body’s natural protective mechanism against sun burn by thickening the skin & producing Melanin.¹

- Protection of the skin by radiation-screening agents

 Anytime light interacts with some material, 3 things can happen. The light can be transmitted, it can be reflected, or it can be absorbed

 If we say that light is “blocked” it means that it is either absorbed or reflected by the material

 

In principle two groups of substances offer themselves as alternatives. One is opaque to radiation and largely reflects the radiation, whilst the other group absorbs the harmful rays but is transparent to the remainder of the radiation.¹

-

Skin type & recommendations for the choice of sunscreens:

 Individuals can be classified into 6 skin types:

 I-Always burns easily; never tans (sensitive).SPF 30-50 II-Always burns easily; tans minimally (sensitive).SPF30-50

 III-Burns moderately ;tan gradually, light brown (normal).SPF15-30 IV-Burns minimally; tans well, moderate brown (normal).SPF10-15 V- Barely burns; trans profusely, dark brown (insensitive).SPF5-10 VI- Never burns ;deeply pigmented (insensitive).Sunscreens None

indicated

SPFSPF= (UV energy required to produce minimal erythemal dose on protected skin) (UV energy required to produce minimal erythemal dose on unprotected skin)

• Similarly,

• SPF= MED(PS) MED(US)

MED is defined as the minimum quantity of radiant energy of specific wave length or range of wavelength which produce the first unambiguous Redding

of human skin 24hr after exposure.

The Sun Protection Factor(SPF):

• SPF Number (Sunburn Protection Factor) measures the strength of UVB protection only. Higher SPF number reflects more protection from UVB, but it doesn’t correspond to UVA protection.(5-50)

• The FDA has just proposed a 4-star UVA rating, previously adopted by Boots, to be included on sunscreen labels.¹

• Highest High Med ★★★★ ★★★☆ ★★☆☆Low★☆☆☆

-Sunscreen Agents

Sunscreen agents can be classified into organic & inorganic sunscreens.

 Organic Sunscreen: Organic ingredients involve carbon and hydrogen atoms. Hydrogen,

oxygen & nitrogen atoms are also often involved. They exist as individual molecules.

Molecules capture energy from the sun’s UV rays . Electrons capture the energy from UV rays. They jump to higher energy levels. The energy give the molecule thermal motion (vibrations and rotations), the energy is released and re-emitted as harmless long wave infra-red rays¹.

Each organic ingredients has a specific absorption range. Organic molecules only absorb UV rays whose energy matches difference between electron energy levels.

 Using more than one kind of sunscreen ingredients gives broader protection as they have different peaks and ranges of absorption.

Most organic ingredients that are currently used were selected because they are good UVB absorbers.¹ 

: -UV A Sunscreens

1 .Benzpheneones (3,4,8): Benzophenone-3 absorption peak is (320)nm used as UVA up to 10%,

it may combined with UVB to give broad spectrum protection.2 .Anthrnilates:

Menthylanthrnilates it is usually used as UVA, the absorption peak at (336)nm & can be used up to 5%.

3 .Avobenzone (also known as Parasol 1789) is not intrinsically photostable and requires photostabilizers to prevent significant degradation in light.

4 .Ecamsule (Mexoryl SX) is a new sunscreen ingredient designed to absorb UVA rays. Ecamsule (trade name Mexoryl SX, INCI terephthalylidene dicamphor sulfonic acid) is an organic compound. It is a benzylidene camphor derivative, many of which are known for their excellent photostability. (meaning it doesn't degrade significantly when exposed to light).¹

Although there are a few different UV absorbers with the trade name Mexoryl, only two of them are widely used where approved. Mexoryl SX (water soluble) and Mexoryl XL (INCI Drometrizole trisiloxane, oil soluble). Together they show a synergistic effect in protection.The patents are held by L'Oréal. Sunscreens containing ecamsule are exclusive to L'Oréal and its brands.¹

-UV B Sunscreens

1 .P-Amino Benzoic Acid (PABA) derivatives : The most commonly used is Padimate Octyl Dimethyl PABA, the

allowable level is 8% & the absorption peak is (311)nm.

2 . Cinnamate derivatives: e.g.: 2-ethylhexyl-P-methoxycinnamate (Octyl Methoxy

Cinnamate), the allowable level is 10% & the absorption peak is (311)nm.

Estrogenic effects were noted in laboratory animals at concentrations close to those experienced by sunscreen users . However, a more recent study concluded that octyl methoxycinnamate and other sun screening agents do not penetrate the outer skin in sufficient concentration to cause any significant toxicity to the underlying human keratinocytes.¹

3-Salicylate derivatives : Such Octyl salicylate & the allowable level is 5%. Homosalate

(Homo methyl salicylate), absorption max. 306nm, 10-15%4 .Octocrylene (Cyno diphenyl acrylic acid, ethylhexyl ester):

Its allowable level up to 10% & has absorption max. 303nm. The extended conjugation of the acrylate portion of the molecule absorbs UVB and short-wave UVA (ultraviolet) rays with wavelengths from 280 to 320 nm, protecting the skin from direct DNA damage. The ethylhexanol portion is a fatty alcohol, adding emollient and oil-like (water resistant) properties.

5 -Phenylbenzimidazole , 290-3406 -Octyl triazone [Uvinul] 290-330

Inorganic (physical) sunscreens: 1.Zinc oxide:

2.Titanium dioxide: - These either reflect light depending on the wavelength of the light &

the particle dimensions of the physical sunscreen or absorb UV light.Small particle size (nano size) leads to decrease in skin whitening as more of the longer wavelength light transmitted until little or no reflection occurs.

Inorganic sunscreen ingredients are different from organic ones. This affect the way they absorb UV light.The ionic attraction molecules forms clusters.

Size varies with number of ions in cluster. Typically ~10 nm – 300 nm.Inorganic ingredients come in different cluster or “particle” size.

Different number of ions can cluster togetherInorganic sunscreens appear white on our skin. Many people don’t like how this looks, so they don’t use sunscreen with inorganic ingredients or apply too little to get full protection.¹

Traditional ZnO and TiO2 products appears white because:1 .Their clusters are large (> 200nm). Large clusters can scatter light in many

different directions2.When reflected visible light of all colors reaches our eyes, the sunscreen

appears white. Organic sunscreen molecules are too small to scatter visible lightNanosized inorganic clusters would not scatter visible light as they are smaller (100 nm or less) than that of traditional.

 Nanoparticle sunscreen ingredients are small inorganic clusters that:1-Provide good UV protection by absorbing most UVB and UVA light.

2-Appear clear on our skin because they are too small to scatter visible light.¹

Nanosized ZnO

particles

Large ZnO

particles

~200nm Traditional ~100nm

- Natural alternatives to chemical sunscreens:

Black tea :The study published in the International Journal of Cosmetic Science, reports that erythema appeared after 4 h and reached a peak at 24 h on control site, whereas no erythema was observed in any of the six subjects on black tea gel applied sites. it was concluded that black tea gel protected the skin from a broad range UV (200–400 nm) radiation and can be safely applied on large skin surfaces.

Green tea:(Camellia sinensis) The polyphenols present in green tea are known as epicatechin. The major

epicatechins found are epicatechin ,epicatechin-3-gallate, epigallocatechin and epigallocatechin-3-gallate (EGCG). These epicatechin are antioxidant in nature and have been shown to function as anti-inflammatory and anti-carcinogenic agents in various biological models in vitro and vivo.¹Chronic exposure of human skin to solar UV radiation is the primary cause of cutaneous malignancy.

The two main photo-protective effects of Green Tea are: anti-inflammatory effects and anti-carcinogenic effects.¹

1-Topical application of green tea polyphenols (GTP) or EGCG to the backs of human before UV irradiation result in less erythema development, decreased myeloperoxidase activity and infiltration of leukocytes as compared to UV alone (without GTP or EGCG) exposed skin sites.

2-EGCG was also found to inhibit UVB-induced production of prostaglandin metabolites, which play a critical role in inflammatory disorders and in proliferative skin disease.

 3-Topical application of GTP inhibited photo-carcinogenic and lower tumor burden as compared to non-GTP-fed control animals.

 Green tea, specifically EGCG, has the ability to block UVB-induced leukocyte infiltration in mouse as well as in human skin, and thus may be able to inhibit UVB-induced production of ROS (reactive oxygen species ) by these

infiltrating leukocytes .  Although ROS help the host to destroy invading microorganism, excessive

and uncontrolled production can also damage host tissues and predispose to various diseases. Thus, the application of EGCG may prove helpful in decreasing the harmful effects caused by UVB exposure through decreased ROS production by acting at different active sites of the ROS generating cascade.¹

EGCG treatment of mouse skin before UV exposure results in:1 .Decrease number of hydrogen peroxide producing and inducible nitric

oxide synthase expressing cells, and reduction in the production of hydrogen peroxide and nitric oxide.

2 .Inhibition of UV-induced epidermal lipid peroxidation, which may protect human skin from solar UV light-induced basal cell and squamous cell carcinogenesis and photoaging.

3 .Protection of anti-oxidant enzymes in human skin.4 .Decrease the formation of cyclobutane pyrimidine induced in DNA by

UV radiation. These cyclobutane pyrimidine dimers are critical in initiating the process of UV-induced mutagenesis and carcinogenesis.

 It’s reported that a number of tumors appear to produce IL-10. The immunosuppressive effects of IL-10 might be one possible mechanism by which these tumors escape immunologic control. It was found that application of EGCG before UV exposure reduced the UV-induced production of IL-10 and UV-induced immunosuppression in the skin and draining lymph nodes, and increase the production of IL-12 in draining lymph nodes.¹

- -Artificial Suntan preparation:

1-Artificial suntan preparation stains(walnut juice, henna).

2-Dihydroxy acetone(DHA): - colorless lotion produce gradual tanning within 6 hours of application .

-Investigation showed that: The DHA reacts with free amino groups, in particular with the free amino group in Arginine forming aldehyde-amino products which condense & polymerize to form dark-colored melanoidins.

 3-Photosensitizing Compounds:

 Photosensitizing psoralen reacts on exposure to ultraviolet light to increase the melanin in the skin. Some psoralen-type photosensitizers are used to enhance skin pigmentation or tanning in the treatment of skin diseases, such as vitiligo.¹

 

- Sunscreen Formulation Formulation of Water-proof sunscreen products involves the following recommendations:

1 -Use water- insoluble sunscreens.2-Use high- oil phases.

3 -Use water- resistance resins and film-formers. Silicon oil is extremely resistance to water penetration & easily spread with thin continuous water repellent film formed such dimethicone350, cyclomethicone . More recently other film formers have gained favor as water proofing agents (alkylated polyvinylprolidones are closely related to that found in film former in hair spray).

4-Use minimal levels of hydrophilic emulsifiers .5 -Use water in oil emulsions.

6 -Make an oil in water emulsion invert to water in oil emulsion as it is rubbed into the skin. A new patent applied by Croda International

A composition contains at least one sunscreen and a protein-PVP copolymer. The sunscreen may be organic and/or inorganic, particularly titanium dioxide. The protein-PVP copolymer improves the effectiveness of the sunscreen, resulting in increased SPF values of the composition.¹

-Sun protection factor studyEmulsion rheology is an important factor influencing the effectiveness of sun protection products based on physical sunscreens . An independent study was conducted to evaluate the waterproof sun protection factor (SPF) of a Crodafos CES (It is a phosphate-based conditioning and emulsifying system whose phospholipid-like character creates an ingredient that is naturally substantive to skin as it is chemically similar to the skin’s lipid bilayer¹³) emulsion compared to a nonionic emulsion. Results show that Crodafos CES provides greater oil deposition and improved resistance to wash-off, producing sunscreen preparations with higher static SPFs and more persistent waterproof SPFs.¹Regarding the side-effects of many organic sunscreens, efforts towards developing safer products. In recent study, titanium dioxide (TiO2) was incorporated into solid lipid nanoparticle (SLN) formulations using both classical and novel preparation methods. the use of crystalline lipid particles as active carriers for physical sunscreens offers the possibility of creating more effective and safer sunscreen formulations and gives an opportunity to reduce UV filter content depending on their crystalline structure with no influence on their high UV-protection level.¹

Formulation of Mild sunscreen products involves the following recommendations:

- Minimize emulsifier levels. (Some emulsifying agents can interfere with chemical sunscreen activity, especially when higher SPFs are used)

-Minimize the use of soap systems. (Alkaline) -Minimize the use of preservatives. (Toxicity)

( -Minimize the use of fragrances. (Irritation -Maximize the use of long-chain esters and other mild

ingredients.(Emollients) - Minimize the use of high levels of sunscreen actives.(Higher concentrations of chemical sunscreens potentially irritating)

 The sunscreen market is governed by hot trends concerning the following :

Product claims: -High-SPF

--PABA-free -PABA damages cell DNA, thus

- increasing the risk of skin cancer¹⁵ .--Sensitive skin

-Non-comedongenic-(oil-free ,won't clog pores)

-Board-spectrum -Water proof

 Product forms:

-Sticks, Gels, Pumps and Wipes.¹  

Segmentation: -Infant and toddlers

-Multi-purpose product. -Skin care, hair care, make-up and foundation .

-Sports enthusiasts. -Year-round use.

 The sunscreen market future prospects involve the following-Search for new UV-A activities.

- Encapsulated sunscreens. In Sol-Gel Technologies, the microencapsulation approach loads UV filters into silica shells ,It may help to lower the incidence of contact allergies¹².

-Micro-sponges. Microsponge delivery systems are uniform, spherical polymer particles. Long lasting product efficacy, with improved protection against sunburns and sun related injuries even at elevated concentration and with reduced irritancy and sensitization¹⁶.

--Market segmentation:

a) Melanoma patients :Many cancer patients have sun sensitive skin due to chemotherapy or radiation treatments . Some sunscreens provide broad spectrum UV-A and UV-B

coverage . b) Senior citizens: Seniors only need to apply sunscreen once a day . They should use a broad spectrum sunscreen that blocks both UVA and UVB rays.¹⁷c) Adolescents .“Time-to-reapply“ sensors.¹

References:1-Bassam Amro , Sunscreens, University of Joran,Amman , Jordan ,2011(1-27).

2-Parisi AV, Kimlin MG, Wong JC, Wilson M, Personal exposure distribution of solar erythemal ultraviolet radiation in tree shade over summer,Centre for Astronomy and Atmospheric Research, University of Southern Queensland, Toowoomba, Australia. 2000;45(2):349-56.

3 -Richard L. McKenzie,Lars Olof Björn,Alkiviadis Bais,Mohammad Ilyasd, Changes in biologically active ultraviolet radiation reaching the Earth’s surface, National Institute of Water and Atmospheric Research, NIWA Lauder, PB 50061 Omakau,(2003, 2, 6)

4-BassamAmro, skinlightining,University of Joran,Amman , Jordan ,2011(1,8).5 -Miyamura Y,The deceptive nature of UVA tanning versus the modest protective effects of UVB tanning on human

skin, Res. 2011 Feb;24(1):136-47 .6 -Nita Agar; Antony R. Young (2005). "Review: Melanogenesis: a photoprotective response to DNA

damage?". Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 571(1-2).7 -M. Nathaniel Mead, Benefits of Sunlight: A Bright Spot for Human Health,2008 April; 116(4): A160–A167.

8 -Menter A, Griffiths CE (July 2007). "Current and future management of psoriasis". Lancet 370 (9583): 272–84..9-headcovers.com/685/elta-sunblock-spf-32-3.0-oz.

10 -emedicinal.com/diseases/sunburn.php11-healingcancernaturally.com/healingwithlight6.html.

12 -Divya R. Sambandan, BA,and Desiree Ratner, MD ,Sunscreens: An overview and update , New York, ( J Am Acad Dermatol 2011;64:748-58.),page 7

13-croda.com/home.aspx?d=content&s=157&r=401&p=281014 -dermalinstitute.com/us/news/?p=1266

15-livestrong.com/article/134435-what-is-paba-sunscreen/16-Viral Shaha ,Hitesh Jain , Jethva Krishna,Pramit Patel,Microsponge drug delivery: A Review, Viral Shaha et al. |

Int. J. Res. Pharm. Sci. Vol-1, Issue-2, 212-218, 2010 P(212,216)17-slideshare.net/akstout18/sun-safety-1698273