It’s a joke you’ve probably cracked at one point or another — I’m allergic to the elliptical machine!” Sounds like the ultimate excuse to avoid the gym, right? But for some people, it’s no joke.It’s called exercise-induced anaphylaxis (EIA), and, according to Brian Smart, M.D., an allergist and immunologist at the DuPage Medical Group Asthma and Allergy Center in Glen Ellyn, Ill., it’s quite rare, with rates of under one in 1,000 people.MORE FROM SELF: The 33 Hottest New Workout Classes“Life-threatening episodes and fatalities have been reported, but are quite uncommon with this condition,” he says. “Nonetheless, anaphylaxis is always serious and should be treated as such.” EIA can affect anyone, of any age, race or gender, but Dr. Smart says it’s seen most often in people in their 20s and 30s.Wait — so people are actually, like, ALLERGIC to exercise? Not exactly, says Dr. Smart. “That’s a misnomer — but exercise can trigger anaphylaxis.” Anaphylaxis is a severe, whole-body reaction to a trigger; in the case of EIA, Dr. Smart says symptoms may start at any stage during or even after exercise, but in 90 percent of cases, symptoms start in the first 30 minutes of exercise. “Typical symptoms start with fatigue, itching and flushing, but then may progress to abdominal cramping, nausea, vomiting, labored breathing and choking,” says Dr. Smart.But how do you know if you’re having an anaphylactic reaction to working out, and not just, say, feeling faint from the heat or suffering from cramps thanks to an unwise lunch? “The symptoms of EIA are so overwhelming that simple dehydration or fatigue cannot explain them,” says Dr. Smart. “A reaction to something you ate, like an upset stomach, is also generally milder in severity. Also, there usually is a constellation of symptoms, which usually include rash and/or flushing.” And, says Dr. Smart, “If the episode becomes full-blown, it may include loss of consciousness, cardiovascular collapse and death.”MORE FROM SELF:Fat-Frying Cardio MachinesEIA episodes can begin suddenly even if you’ve never had them before, says Dr. Smart. In fact, he says, “Some people may get milder, non-life-threatening anaphylaxis and may fail to recognize their symptoms for what they are.”Any degree of exercise can cause symptoms, but more intense exercise is more likely to do so, Dr. Smart explains. However, he says, episodes are inconsistent and an intense workout one day may not cause symptoms, while a recovery session another day could cause symptoms.Can EIA be treated? Or are people with this condition doomed to being couch potatoes forever? “Most of those rare people who actually have this condition can exercise, but this needs to be under the direction of a board-certified allergist,” says Dr. Smart. “Medications, combined with careful warm-up and warm-down routines can help.” So, he says, if you suspect you might be affected by EIA, don’t hang up your sneakers — make an appointment with a board-certified allergist.MORE FROM SELF: 11 Ways to Outsmart Spring Allergies