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Dr. Scott Sicherer

How Long Until Someone Starts to Feel Better After Food Allergy Anaphylaxis?

Q: I’m severely allergic to tree nuts and eggs and recently had a frightening anaphylactic reaction in which I had trouble breathing and became covered in hives. I used my auto-injector, had a second dose in the ambulance and required a third dose at the hospital. 
My question: how long does it take for someone’s immune system to return to normal after anaphylaxis? 

Dr. Sicherer: In most cases, serious symptoms of anaphylaxis, including wheezing, trouble breathing, throat tightness, etc., improve with a single dose of epinephrine, and usually within minutes. If serious symptoms are not improving, or recur, more epinephrine may be needed. But this is less common.

Symptoms such as skin rashes or abdominal pain may resolve more gradually, over about an hour or more. It may take longer for swelling, such as swollen eyelids or lips, to get back to normal.

Less often, symptoms may improve but then recur, sometimes with greater severity, which is called a biphasic reaction. The chance of a biphasic reaction is higher if initial symptoms are worse, but it is not entirely predictable. This is why it is recommended to call 911, and go to an emergency room and stay under observation for at least four hours to be sure symptoms have abated. Rarely, anaphylaxis symptoms can be protracted over many  hours or even days.

Almost everyone with anaphylaxis feels much better hours later or by the next day. If that’s not so, any symptoms should be reviewed with your doctor. There is usually no need for additional medications, but be sure to have renewed prescriptions for your expended epinephrine auto-injector.

I recommend reviewing the incident with an allergist to ensure the trigger was properly identified, determine if additional testing is needed, and to review avoidance strategies and emergency response.

Dr. Scott Sicherer is a practicing allergist, clinical researcher and professor of pediatrics. He is Chief of the Division of Allergy and Immunology, Jaffe Food Allergy Institute, at the Icahn School of Medicine at Mount Sinai in New York. He is also the author of Food Allergies: A Complete Guide for Eating When Your Life Depends On It.

Send your question to Dr. Scott Sicherer by email.
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