Imagine a woman having a few drinks a night, having a little ibuprofen in the morning for her hangover and going for a run. She never had a problem with alcohol, ibuprofen or exercise before. But this time, some combination of the three triggers a life-threatening allergic reaction known as anaphylaxis.
This is a real case that happened to a patient of Dr. Andrew Murphy, an allergist at Suburban Allergy Consultants in Pennsylvania. So, is it possible to be allergic to exercise?
Not technically, said Murphy. When a person is exposed to something they are allergic to, a protein from the allergen, for example, peanuts, grass or cat hair, interacts with antibodies in immune cells in your body. Immune cells trigger chemicals such as histamine, which cause sneezing, hives, wheezing and other symptoms. No protein enters the body when a person exercises, so you cannot be allergic to running.
But, exercise can trigger the same series of symptoms in people with a rare condition called exercise-induced anaphylaxis. “It is not necessarily mediated by antibodies, but exercise is a trigger and allergy [immune] the cells are still activated, “Murphy told Live Science.
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Exercise alone is enough to trigger an allergic reaction in some people, but the way you do it is unknown. One theory proposes that exercise causes the release of endorphins, which causes certain immune cells to release chemicals such as histamine, according to a 2010 review in the journal. Current Allergy and Asthma Reports.
Other people, like Murphy’s patient, have a condition known as food-dependent exercise-induced anaphylaxis, or FDEIA. For them, eating a certain food before training can cause symptoms such as wheezing or hives – even if they don’t react to that food when they rest. In the case of Murphy’s patient, the “food” was alcohol, ibuprofen, or a combination of the two. There are several theories as to why certain foods in combination with exercise can cause an allergic reaction, including that working out makes the gastrointestinal tract more permeable, allowing allergens to get in better contact with the immune system. Ibuprofen can further increase the permeability and uptake of foreign allergens throughout the body and can interact directly with immune cells, according to the review.
Exercise-induced anaphylaxis is rare. About 2% of people in the western world suffer from anaphylaxis and 5% to 15% of cases are exercise-induced, according to the review. The food-dependent version of the disease is less common and accounts for between a third and a half of all cases. Not many children come to the office with any of these conditions, said Murphy, and it usually appears in teenagers and adults.
Treatment for food-dependent exercise-induced anaphylaxis is simple: don’t eat for four hours before and after training, according to a review in the magazine Specialized review of clinical immunology. Another option is to avoid trigger foods entirely, if these foods are known.
When exercise is the only trigger, controlling the disease can be more difficult than controlling FDEIA, but doctors can help patients develop specialized exercise regimens, said Murphy. The amount of effort that a person with the disease can safely make varies. A casual walk can cause a reaction in some people, but others can ride a bicycle without problems. Each patient must work with a doctor to discover their own limits. Murphy always prescribes an EpiPen in an emergency, and antihistamines can help prevent episodes, according to a 2001 review in the magazine. American Family Physician.
Serious reactions in response to exercise are rare. In 25 years of practice, Murphy has seen only one person pass out. “I tend to see more people with skin problems [skin-related] symptoms like hives, swelling of the lips or wheezing with it, “he said.
Originally published on Live Science.