By Melissa Dahl

Does all that exertion on the elliptical machine make you
nauseous? Have you ever been convinced that if you spend even one more
minute on the treadmill, you will actually die? Maybe it’s not all in your
head.

A few people are actually allergic to exercise, and in
very rare cases, a sweaty workout could be enough to kill them.

Exercise-induced anaphylaxis is a fairly rare condition
which can cause hives, fainting, vomiting and difficulty breathing during a
workout, and the symptoms can last up to four hours after it. In some cases,
it can be triggered by certain foods eaten before exercise, like peanuts,
shellfish, eggs or even, in two reported cases, celery. But this isn't just your
average food allergy, an expert explains.

"These are people who will not have this reaction unless
they exercise right after eating this food," says Dr. Jacqueline Eghrari-Sabet,
an allergist in private practice in Montgomery Village, Md., and a spokeswoman
for the American Academy of Allergy, Asthma and Immunology. "Eating shellfish
and sitting there? Nothing. But eating shellfish and exercising? For these
people, it's bad news."

As you exercise and your heart rate speeds up, your blood
starts whizzing through organs much faster, and therefore more frequently, than
it normally does. With every trip your blood takes to your stomach, it's picking
up more, say, celery bits. For those with exercise-induced anaphylaxis, the
normal amount of celery antigens picked up by the blood isn't enough to bother
them. But while exercising, the extra celery bits their blood is picking up
causes an allergic reaction.

Running and jogging are the most likely to trigger an
attack, but other strenuous activities like dancing, volleyball, skiing and even
yard work can also cause a reaction.

Since the 1970s, only 1,000 cases of exercise-induced
anaphylaxis have been documented – and among those cases, one death. Experts
believe that’s because many people with this condition are able to recognize the
symptoms quickly and keep it under control by waiting a couple hours after they
eat to work out and bookending their workouts with a slow warm-up and cool-down.

"It'll usually happen when you're really exercising," says Eghrari-Sabet. "I don't think you're going to get it when
you're bowling. But if you're doing cardio or a hip hop class, then, yes."

Others suffer from the less serious exercise allergy
cholinergic urticaria, a common type of heat rash, which differs from
anaphylaxis in that it starts and ends with the skin reaction – no nausea or
difficulty breathing for these folks. Ten to 20 percent of the population will
experience some form of it during their lives. Besides exercise, sun exposure,
spicy foods or even getting too emotionally worked up can cause an itch attack.

The condition can strike spontaneously, so even if you’ve
been exercising all your life with nary a rash, you can unexpectedly break out
in hives. Even some marathon runners have suddenly come down with a bad case of
the itches after jogging, explains Eghrari-Sabet. Women are most susceptible to
the condition, and the average age for its first appearance is 16. (A handy way
to get out of gym class?)

Unfortunately for people seeking an excuse not to break a
sweat, most dermatologists and allergists send their patients with
exercise-related allergies right back to the locker room.

“If they come to me, I’m not going to tell them not to
exercise,” says Dr. Bruce Robinson, a Manhattan dermatologist.  Instead he
advises patients to pick a less strenuous regimen or a cooler place to work
out.

Because the itchy sensation happens when body temperature
suddenly rises, it can be eased by warming up and cooling down slowly, before
and after every workout. Or try swimming for your normal cardio routine, which
will keep the body temperature cool. If a food allergy is the culprit, don’t eat
for a couple of hours before your workout.

Although serious side effects are rare, some experts
believe, that exercise-induced anaphylaxis often goes undiagnosed. So if you
start to feel itchy while working out, watch out. It’s probably best to avoid
death by treadmill at all costs.