Health & wellness

Health answers: What is anaphylaxis?

Q. What is anaphylaxis and what should you do if someone is having it?

A. Anaphylaxis is a severe and potentially life-threatening allergic reaction. Compared with other allergies, “the scale is much greater,” said Dr. David Hong, an allergist and immunologist at Brigham and Women’s Hospital. It is systemic (involving the entire body) rather than localized to one spot, and usually happens suddenly. The most common triggers are specific foods (peanuts, tree nuts, shellfish, dairy products), insect bites and stings, and medications.


Typical symptoms are swelling, hives, and difficulty breathing or swallowing. Anaphylactic shock refers to a sudden drop in blood pressure in someone experiencing anaphylaxis, which can cause dizziness, loss of consciousness, and even death. Hong says that asthmatics are especially at risk of bad outcomes because their airways constrict.

There is one critical treatment for anaphylaxis: an epinephrine shot. It’s delivered to the thigh muscle and delivers relief within seconds.

People with a known risk for anaphylaxis should get an epinephrine auto-injector (such as an EpiPen) from their doctor and keep it with them at all times. “It’s important for patients and their friends and family to know how to use an EpiPen,” Hong says. The device is relatively simple and is designed to go through clothing. People often feel afraid to deliver an injection, but leaving anaphylaxis untreated is far more dangerous. “It doesn’t hurt to use the EpiPen out of caution,” he says. If an epinephrine shot is unavailable, seek emergency medical help immediately.

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