Anaphylaxis

A life-threatening allergic reaction (anaphylaxis) can cause shock, a sudden drop in blood pressure and trouble breathing. In people who have an allergy, anaphylaxis can occur minutes after exposure to a specific allergy-causing substance (allergen).

In some cases, there may be a delayed reaction or anaphylaxis may occur without an apparent trigger.

If you're with someone having an allergic reaction with signs of anaphylaxis:Immediately call 911 or your local medical emergency

number.Ask the person if he or she is carrying an epinephrine

autoinjector (EpiPen, Auvi-Q, others) to treat an allergic attack.

If the person says he or she needs to use an autoinjector, ask whether you should help inject the medication. This is usually done by pressing the autoinjector against the person's thigh.

Have the person lie still on his or her back.Loosen tight clothing and cover the person with a

blanket. Don't give the person anything to drink.

If there's vomiting or bleeding from the mouth, turn the person on his or her side to prevent choking.

If there are no signs of breathing, coughing or movement, begin CPR. Do uninterrupted chest presses — about 100 every minute — until paramedics arrive.

Get emergency treatment even if symptoms start to improve. After anaphylaxis, it's possible for symptoms to recur. Monitoring in a hospital for several hours is usually necessary.

If you're with someone having signs and symptoms of anaphylaxis, don't wait to see whether symptoms get better. Seek emergency treatment right away. In severe cases, untreated anaphylaxis can lead to death within half an hour.

An antihistamine pill, such as diphenhydramine (Benadryl), isn't sufficient to treat anaphylaxis. These medications can help relieve allergy symptoms, but work too slowly in a severe reaction.

Signs and symptoms of anaphylaxis include:

Skin reactions, including hives, itching, and flushed or pale skin

Swelling of the face, eyes, lips or throatConstriction of the airways, leading to

wheezing and trouble breathingA weak and rapid pulseNausea, vomiting or diarrheaDizziness, fainting or unconsciousness

Some common anaphylaxis triggers include:MedicationsFoods such as peanuts, tree nuts, fish and

shellfishInsect stings from bees, yellow jackets,

wasps, hornets and fire antsIf you've had any kind of severe allergic

reaction in the past, ask your doctor if you should be prescribed an epinephrine autoinjector to carry with you.

Treatments and drugs

During an anaphylactic attack, an emergency medical team may perform cardiopulmonary resuscitation (CPR) if you stop breathing or your heart stops beating. You may be given medications including:

Epinephrine (adrenaline) to reduce your body's allergic response

Oxygen, to help compensate for restricted breathingIntravenous (IV) antihistamines and cortisone to

reduce inflammation of your air passages and improve breathing

A beta-agonist (such as albuterol) to relieve breathing symptoms

Case history #1A 14-year-old girl presents in severe respiratory distress to

the emergency department. Her past medical history includes asthma and a peanut and tree nut allergy. Shortly after ingestion of a biscuit in the school cafeteria, she began complaining about flushing, pruritus, and diaphoresis followed by throat tightness, wheezing, and dyspnoea. The school nurse called an ambulance.

No medications were administered and the patient did not have the epinephrine (adrenaline) pen prescribed by her allergist. Her physical examination reveals audible wheezing and laryngeal oedema and an oxygen saturation of 92%.