Peanut Allergies and Delayed Anaphylaxis

Medically reviewed by Daniel Murrell, MD on November 29, 2017Written by Stephanie Watson

Peanut allergies

If you have a peanut allergy, your immune system will launch an attack anytime it senses the proteins in peanuts. This will cause the release of chemicals that trigger symptoms like itchy hives, nausea, or facial swelling. Peanut allergies are common in the United States.

Some people have severe peanut allergies. When they’re exposed to even the tiniest trace of peanuts, they develop a life-threatening total-body reaction called anaphylaxis.

An anaphylactic reaction often starts within seconds after someone with a severe allergy eats peanuts. Rarely, symptoms can appear minutes or hours after exposure.

You can be treated for a severe reaction, think you’re perfectly fine, and then develop a second reaction hours or days later without being exposed to peanuts again. A reaction that occurs long after you’ve been exposed is called delayed or late phase (biphasic) anaphylaxis.

Learn why this type of response is so dangerous, and find out how to prevent it from happening to you or your child.

Symptoms of a delayed anaphylactic reaction

Symptoms of a delayed anaphylactic reaction can show up an hour or more after you were exposed to peanuts. Some people don’t start to see symptoms until a few days later.

Common anaphylaxis symptoms include:

  • swollen face, eyes, lips, or throat
  • wheezing or trouble breathing
  • weak, fast pulse
  • pale skin
  • confusion
  • sudden feeling of body warmth
  • dizziness or fainting
  • itchy skin
  • hives
  • vomiting
  • diarrhea
  • cramps

The symptoms of a delayed reaction can be more or less severe than symptoms of an immediate reaction.

Who gets delayed anaphylactic reactions?

A 2015 study found that 2 percent of people treated for an allergic reaction at hospital emergency rooms developed a second, late reaction. That delayed reaction occurred, on average, 15 hours after people were first treated. Another study found that about 15 percent of children had a second severe allergic reaction hours after their first reaction.

You’re more likely to have a delayed reaction if you:

  • have a severe peanut allergy
  • don’t get treated with epinephrine quickly enough
  • don’t get a large enough dose of epinephrine
  • don’t respond quickly to epinephrine
  • have low blood pressure during your first reaction
  • have a history of delayed anaphylaxis

Dangers of delayed anaphylaxis

Some allergic reactions are mild, but anaphylaxis is a very serious condition. Your airways can tighten to the point where you can’t breathe. People with anaphylaxis can die within a half hour if they don’t get medical help.

In some cases, people who’ve been treated for an allergic reaction and seem completely fine develop a reaction hours later. In 2013, 13-year-old Natalie Giorgi ate a small bite of a peanut-laced dessert while on summer vacation with her family. She received three doses of epinephrine, a medication that helps reverse the symptoms of an allergic reaction. Natalie seemed fine afterward, but she died of a severe allergic reaction later that evening.

How to avoid a reaction

If you know you have a severe peanut allergy, the best way to prevent anaphylaxis is to avoid them. Here are a few tips:

  • Every time you shop, read food labels carefully. Packaged foods that contain peanuts are required to include them in the ingredients list.
  • When you order food in restaurants, always let the server know that you have a peanut allergy. Ask for your food to be prepared without peanuts, peanut oil, and other peanut-based products.
  • When traveling by plane, contact the airline and alert them to your allergy ahead of time. You can request that your flight be peanut-free and ask to have your seat cleaned.

As a precaution, always keep an epinephrine auto-injector (such as an EpiPen) nearby. This medication can reverse the symptoms of an anaphylactic reaction, but you have to use it quickly for it to be effective.

During a delayed reaction, you may need to administer a second and possibly third dose of epinephrine. See your allergist to learn how to use the auto-injector correctly.

After you inject epinephrine and your symptoms stabilize, go to an emergency room for treatment. Always get medical help to prevent another reaction.

When to see your doctor

Anyone who has had an allergic reaction to peanuts should see an allergist. They’ll review your medical history and symptoms, give you tips on how to avoid peanuts, and determine whether you need to keep an epinephrine auto-injector on hand for emergencies.

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