Woman in front of 3 doors with her hands out. She's indicating that she doesn't know the answer to her allergy issue.

When it comes to our health, today’s world of information overload leads us to believe that every mysterious symptom can be identified, every problem solved. But sometimes it’s not that easy.

Anaphylaxis is a severe allergic reaction that comes on swiftly and can turn deadly in minutes. Often the cause is obvious: the unexpected peanuts in the cookie; the shellfish mixed into soup; the latex balloons at the party table.

For people with no previously diagnosed allergy, anaphylaxis can be the beginning of a detective search worthy of the great Sherlock Holmes himself.

When there is no obvious or apparent cause of a reaction, it is termed idiopathic anaphylaxis.

It’s critical that people at risk for anaphylaxis – whether the cause is known or not – always carry two epinephrine auto-injectors with them at all times. Epinephrine is the first line treatment for any anaphylactic reaction and the only medication that effectively stops symptoms.

Allergy & Asthma Today spoke with Dana Wallace, MD, board-certified allergist at Florida Center for Allergy and Asthma Care in Fort Lauderdale, Florida and an Anaphylaxis Community Expert (ACE) volunteer, about idiopathic anaphylaxis and what patients need to know.

Q: What should a patient do if the cause of an anaphylactic reaction is unknown?

A: Any time a person experiences anaphylaxis, they should consult with a board-certified allergist for an in-depth evaluation. When the cause of the allergic reaction is not obvious, the process will likely take several visits, extensive discussion and allergy testing.

Q: What investigative steps can patients take to find out the cause of an anaphylactic reaction?

A: When anaphylaxis symptoms occur, write down a list of all recent activities, especially foods, beverages and medications encountered or consumed within the previous 24 hours.

If the severe reactions occurred after a meal, get a detailed ingredient list of all food consumed. If your meal was eaten out, ask the restaurant for it; for home-cooked food, keep all labels and the remaining food product, if possible, especially if it is a newly opened package or is very old.

With each episode of anaphylaxis, these lists should be compared to identify similarities or patterns.

Write down a detailed description of your symptoms and when they occurred in relation to potential triggers – and ask a friend or relative who was with you to jot down their observations as well. If you went to the emergency department for treatment or observation, your allergist will need to review those medical records.

Some questions your allergist may ask:

Did anaphylaxis occur immediately after eating a meal or 2-5 hours later? What foods were consumed and was it a restaurant meal?

Did it occur soon after taking a medication such as aspirin or ibuprofen?

Were you outside in a setting where insect stings might occur?

Were there extreme hot or cold temperatures?

Did it occur during or after exercise?

Q: What type of testing is involved?

A: The allergist will likely want to do extensive testing for a wide range of food and other allergens. This could include testing specific foods that the patient will be asked to supply, such as spices used, packaged food, or even leftover restaurant food. Both skin tests and blood tests might be ordered.

The allergist will also test for underlying diseases that mimic anaphylaxis. If after an exhaustive evaluation no cause is determined, the diagnosis is idiopathic anaphylaxis.

While allergists search for a cause, patients with frequent episodes (six or more times per year) may be placed on daily antihistamines or short courses of oral corticosteroids to minimize possible reactions. Patients with infrequent reactions (less than five episodes per year) do not usually need daily medications, but this may vary depending on past episodes.

Reviewed by Michael Mellon, MD and Bradley Chipps, MD