Anaphylaxis: the Basics

Medically Reviewed by Sabrina Felson, MD on October 31, 2021
3 min read

This serious, sometimes life-threatening allergic response is marked by swelling, hives, lowered blood pressure, and dilated blood vessels. In severe cases, you could go into shock. If anaphylactic shock isn't treated immediately, it can be fatal.

This condition starts in your immune system. Your body creates a protein (you might hear it called an antibody) called immunoglobulin E or IgE to fight allergens. It kicks off an over-the-top reaction to something that should be harmless, like certain foods.

Your body may not react the first time you come across this substance, but it could produce antibodies later on. When you come in contact with it again, the allergen binds to these antibodies, and your body churns out more symptom-causing chemicals called histamines. That brings on the anaphylaxis.

It might begin with severe itching of the eyes or face. Within minutes it could get more serious. You could find it hard to swallow or breathe. It can also affect your stomach -- you might have belly pain, cramps,vomiting, or get diarrhea. Your skin could be involved too, with hives (itchy red welts), and angioedema, a swelling that’s like hives but shows up under your skin.

Food is most often to blame. Nuts, shellfish (shrimp, lobster), dairy products, egg whites, and sesame seeds are common triggers. So are wasp or bee stings.

Sometimes exercise can cause it, if you’re active after you eat a trigger food.

Some medications are also on the list.

Pollens and other allergens you breathe in rarely cause anaphylaxis.

Some substances can cause reactions -- called anaphylactoid reactions -- that are similar to and just as serious as anaphylaxis, but don’t involve IgE antibodies. The most common triggers:

The symptoms are the clue. If you have a history of allergic reactions, you’re more likely to have severe problem in the future. Skin tests may help your doctor figure out the root cause.

There’s only one fast-working method: a shot of epinephrine, or adrenaline. It can stop your symptoms on a dime. Most people take it with a device called an auto-injector -- it lets you give yourself the shot. The best place to do it is in your thigh.

If you think you’re having this type of reaction, don’t wait to give yourself the shot. Do it even if you aren’t sure allergies are to blame. It won’t hurt you to take it just to be safe.

The same rule applies if you’re near someone who seems to be going into anaphylactic shock. If you know they have an auto-injector and they can’t use it, do it for them. Then call 911. Some people need CPR and other lifesaving measures.

Treatment also includes fluids into your veins and medicines that help your heart and circulatory system. Once you’re stable, you’ll get antihistamines and steroids to also help control your symptoms.

If you have anaphylaxis, get emergency medical care immediately. The condition can quickly lead to an increased heart rate, sudden weakness, a drop in blood pressure, shock, and ultimately unconsciousness and death.

If you’re allergic to bee stings or anything else that could bring on anaphylaxis, ask your doctor to prescribe an epinephrine injection kit. Carry two with you at all times.

The best way to avoid a reaction is to stay away from triggers you know about. Tell your doctor about any drug allergies before you get any kind of health care treatment, even dental work.

It’s also a good idea to wear a medical alert bracelet or pendant, or carry a card that identifies your allergy. In an emergency, it could save your life.