7 Surprising Triggers of Anaphylaxis

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On August 14, 2025

1. Exercise — on Its Own or With Food, Pollen, or Medication

Symptoms of exercise-induced anaphylaxis can include extreme fatigue, warmth, flushing, wheezing, itching, hives, or facial swelling during or shortly after physical activity. Anaphylaxis can also be triggered by moderate activities such as brisk walking, or vigorous yard work.

This form of anaphylaxis is difficult to diagnose and is estimated to make up 2 to 5 percent of all cases of anaphylaxis worldwide.

“It’s very, very rare,” says Torbati. “I can count on one hand the number of times I have seen it in 30 years of practice.”

In some instances, exercise alone triggers anaphylaxis. In others, exertion combined with a food eaten just before a workout can cause anaphylaxis — and the symptoms can come on suddenly.

“A person can go jogging every day of the week and be fine,” then eat a certain food before jogging and have a reaction, says Scott H. Sicherer, MD, a pediatric allergist and immunologist at Mount Sinai Medical Center in New York City.

Other potential triggers, in combination with exercise, can be pollen or medication, such as penicillin or aspirin. To make diagnosis even more confusing, your response may not be consistent. A severe reaction may happen repeatedly or only sporadically, says Dr. Sicherer.

If you’ve experienced anaphylaxis while exercising, there’s some precautions you can take:

Work out with a friend who can administer treatment and get help.
Avoid exercise in extreme temperatures.
Restrict exercise outside during allergy season.
Avoid trigger foods before exercising.
Take your epinephrine and seek medical help if you feel your symptoms coming on.

2. Semen

Sperm allergy, also called semen allergy, is a rare cause of anaphylaxis but can cause life-threatening symptoms during or after intercourse. While men can be allergic to semen — a rare condition known as post-orgasmic illness syndrome — the allergy is most common in women, and anaphylaxis caused by semen has largely been studied in women.

The allergy seems to be more common in women who have allergic asthma (asthma triggered by allergies) or atopic dermatitis (a skin disorder sometimes caused by allergens).

In some cases, the anaphylactic reaction occurs because the woman’s partner ate something or took a drug that she’s allergic to, which is then transferred through his semen. In other cases, it’s an allergy to seminal plasma protein, a natural component of semen.

After contact with semen, a woman may experience serious anaphylactic symptoms ranging from itching and hives to shortness of breath, throat swelling, wheezing, pelvic pain associated with uterine contractions, low blood pressure, or loss of consciousness.

To prevent this reaction, use a condom (but remember that latex can also trigger an allergic reaction), and ask your partner to avoid eating foods or using medications that you’re allergic to.

3. The Menstrual Cycle

Some women experience a rare form of anaphylaxis just before or during their menstrual cycle. Known as catamenial, or cyclic, anaphylaxis, this rare disorder often goes unrecognized.

In some cases, the culprit is a medication or food consumed around the time of menstruation. But in a study of females under 30, no triggers were identified other than menstruation.

According to that study, catamenial anaphylaxis can often be controlled by a hormone called medroxyprogesterone, which regulates ovulation and menstruation. Some may find relief from symptoms after a salpingo-oophorectomy, a procedure in which the fallopian tubes and ovaries are removed. Administration of a cyclooxygenase inhibitor was also found to be effective.

If you suspect you have catamenial anaphylaxis, you should be evaluated by an allergist. Skin prick testing may be done to rule out food allergies. Your doctor’s questions may help uncover the link between anaphylaxis and your menstrual cycle.

The study also suggests that patients should complete a symptom diary, as well as a menstrual chart, to distinguish whether the anaphylactic episodes happen the week before menstruation, in the first few days of the cycle, or without any regard to the cycle.

4. Latex

The more you’re exposed to latex, the more likely you are to develop an allergy to it.
In a wide-ranging European study of anaphylaxis cases from 2002 to 2020, 30 percent of cases were caused by latex.
“Usually people develop itching, swelling, and redness in their hands,” says Torbati. “Other systemic symptoms might be swelling in the throat, wheezing, or a drop in [blood] pressure. It can happen often in hospitals, so we carry latex-free gloves.”

If you’re a healthcare worker, hairdresser, or housekeeper who wears latex gloves, you’re at a higher risk for a latex allergy. If you have to wear latex, look for gloves that are powder-free, since they contain less latex protein — the substance that causes the allergic reaction. Wash your hands with soap and water after removing them.

If you are sensitive or allergic to latex, let healthcare workers know so you can have medical or dental procedures performed with latex-free supplies.

5. Red Meat

Meat from mammals — beef, pork, lamb, veal, venison, rabbit, and others — can cause symptoms of anaphylaxis hours after eating it, making it difficult to draw a connection between the food and allergy.

With most other allergies, “it’s unusual to have anaphylaxis hours after exposure,” Sicherer says. But with this form of anaphylaxis, you may not experience symptoms until three to six hours later, he says. That’s because it takes time to digest the meat.

People in the United States tend to develop this allergy after getting a bite from a lone star tick, though other ticks, such as the blacklegged tick or western blacklegged tick, have also been associated with the condition. When someone is bitten by one of these ticks, a molecule known as alpha-gal may be transferred through the tick’s saliva. Alpha-gal is naturally produced in mammals, but not in humans, which can cause the immune system to trigger an allergic reaction. This is known as alpha-gal syndrome.

This form of anaphylaxis is more common in woodsy southeastern states where ticks thrive.

6. Insect Stings

As many as 90 to 100 people in the United States die each year because of a severe allergic reaction to an insect sting.

Bees, hornets, wasps — including yellow jackets — and fire ants are the most likely insects to cause a severe anaphylactic reaction. You may not have a reaction to your first or second sting, says Torbati. But in some individuals, after the first sting, their immune system may overreact to the insect venom and produce specific antibodies called immunoglobulin E (IgE). If stung again by the same type of insect, the venom may interact with the antibodies, triggering an allergic reaction.

If you’ve ever had an anaphylactic reaction to a sting, you should carry an epinephrine auto-injector and take steps to prevent stings, such as:

Wear clean, light-colored clothing when outdoors. Avoid bright colors such as yellow and orange.
Avoid perfume and scented toiletries.
Cover up as much of your body as possible with clothing.
Wear closed-toe shoes outdoors.
Stay away from food and garbage when outdoors.
Remain calm if a single stinging insect is flying around.

You can also ask your doctor about venom immunotherapy, where you’re regularly exposed to small amounts of the venom in a clinical setting until your immune system no longer reacts to a full-size dose of it.

7. Unknown Reasons

Sometimes, anaphylaxis happens for unknown reasons.

“A person is sitting there, watching TV, and has an allergic reaction,” says Sicherer.

If you have a sudden and unexplained allergic reaction, your doctor will probably take a complete history and ask a lot of questions, such as: What did you eat or drink? Did you exercise? Did you take medication?

But sometimes, you’ll never know what triggered it. This situation baffles doctors and patients, but it’s not uncommon.

In fact, 30 to 60 percent of people with anaphylaxis may have had a reaction that can’t be explained by a known trigger, according to one study. And there is no test available that can tell you, for example, what type of insect bit you if you are having a reaction, says Torbati.

If you have a history of reactions to unknown triggers, it’s important to carry an epinephrine auto-injector with you.

“You can’t always prevent anaphylaxis,” says Torbati. But you can recognize the signs and treat it right away.

The Takeaway

In anaphylaxis, your immune system reacts to a food or substance as if it’s a harmful invader and your body releases a flood of chemicals that cause allergy symptoms.
While common triggers are food and insect bites, anaphylaxis can also be caused by medicine, and in rarer cases, exercise, semen, the menstrual cycle, and other triggers.
Anaphylaxis is unpredictable, but treatable with an injection of epinephrine. If you are susceptible to anaphylaxis, you should carry an epinephrine auto-injector with you at all times. If you have a reaction, inject epinephrine and go straight to the emergency room.

Additional reporting by Nina Wasserman and Quinn Phillips.