What Is Idiopathic Anaphylaxis?

Reviewed by Carol DerSarkissian on May 22, 2019

When you have anaphylaxis, your body has a potentially life-threatening response to an allergy trigger. But if your doctor calls it "idiopathic" anaphylaxis, it means cause for the reaction isn't known.

Either way, the symptoms can be the same. They include a swollen throat, lower blood pressure, and shock.

If you have anaphylaxis, you need medical help right away with an epinephrine shot. You'll need to go to the emergency room.

What Happens During Idiopathic Anaphylaxis

You may have a partly blocked airway due to a swollen tongue or throat. It's possible you could pass out.

Other symptoms can include wheezing or breathing problems, hoarse voice, and trouble swallowing.

Skin changes you might get include rash, welts, hives, or pale coloring. Your may also have swelling around the eyelids, mouth, or genitals.

Other symptoms are vomiting, diarrhea, and stomach cramps.


An allergist or immunologist can make a diagnosis of idiopathic anaphylaxis only after other causes have been ruled out.

Some common causes of anaphylaxis that your doctor might want to rule out are allergic reactions to foods like:

  • Shellfish and fish
  • Peanuts and tree nuts
  • Milk
  • Eggs
  • Wheat


Other common triggers include:

Less common causes are:

  • Lupin -- seeds that are milled into flour and used in some baked goods
  • Flour contaminated by mites
  • Oleosins -- allergen found in sesame seeds
  • Exercise
  • Cold temperatures
  • Delayed reaction to red meat

To help identify possible triggers, your doctor may get your medical history, do a physical exam, and do allergy testing.

To help your doctor make a diagnosis, you may want to track the details of each incident of anaphylaxis. Here are some things to note:

  • Your location
  • Time
  • What you ate in the hours before
  • What medications you'd taken in the hours before
  • Your overall health
  • Whether you were hot, cold, or stressed
  • Whether you exercised before the reaction

Prevention and Treatment

Because you don't know the cause of an idiopathic anaphylactic reaction, you cannot avoid triggers and prevent incidents entirely. But you can make sure you are prepared for future reactions. You should:

  • Always carry an epinephrine injector
  • Teach yourself and others how to use the injector
  • Wear medical ID jewelry


Also talk with your doctor about each medication that you use to see if it could be a trigger, and discuss whether continuing it is a good idea.

Another helpful idea is to create an anaphylaxis emergency action plan. Keep it on file at work so that your co-workers can recognize your symptoms and give you treatment.

It's not clear why, but many people with idiopathic anaphylaxis -- even those with especially severe, life-threatening symptoms -- gradually improve and have fewer reactions over time.

If your reactions continue or start to happen more often, or if your symptoms become more serious, your allergist or immunologist may recommend medications such as:

WebMD Medical Reference



American Academy of Allergy Asthma & Immunology: "Anaphylaxis," "Idiopathic Anaphylaxis Definition," "Anaphylaxis Emergency Action Plan."

The Journal of Allergy and Clinical Immunology: "Idiopathic Anaphylaxis."

Anaphylaxis Campaign: "Idiopathic Anaphylaxis: The Facts."

Asthma and Allergy Foundation of America: "Anaphylaxis in America."

Current Treatment Options in Allergy: "Idiopathic Anaphylaxis."

Mayo Clinic: "Anaphylaxis."

© 2019 WebMD, LLC. All rights reserved.