10 Weird and Surprising Allergens


You’re probably familiar with allergies to mold, pollen, and pets. But what about allergies to water, shoes, and exercise? Get the scoop on these and other highly unusual, sometimes imagined, allergies.

Allergy Outliers

Allergies are a fact of life for many people, affecting an estimated 17 million adults and 7 million children in the United States (allergic conditions are the most common health issues affecting children). Allergies occur when your body’s defense system overreacts to a foreign substance called an allergen, resulting in symptoms that range from sneezing and watery eyes to body rashes and, in severe cases, life-threatening anaphylaxis.

Allergies can be seasonal, such as a pollen allergy that gets worse in spring and summer, or perennial, such as an allergy to cats or peanuts that persists year-round. The best way to manage allergies is to avoid or eliminate exposure to the allergen, and to treat symptoms by taking over-the-counter or prescription medication.

The most common allergens are animal dander, food, pollen, dust, and mold, so it may surprise you to learn that you can develop allergies to all kinds of odd things. While you can’t really be allergic to, say, your job (sorry about that), it may not be your imagination if you think you are allergic to your shoes. Here are a few other weird and surprising allergens to be aware of.

Your Shoes: Leather Allergy

If you get a poison ivy-type rash on your feet after wearing leather shoes, you could be allergic to chemicals used in the leather tanning process. “This type of allergy is called contact dermatitis (a form of eczema), and you can diagnose it by doing a patch test,” says Linda Ford, MD, an allergist at the Nebraska Medical Center in Omaha and past president of the American Lung Association. Contact dermatitis is a catchall term for a common skin condition that can result from contact with many possible allergens or irritants. Its rashy reaction leads to more than five million doctor visits every year. The solution to a shoe allergy — contact dermatitis of the feet — is to wear socks or shoes made with something other than leather. Antihistamines can help with the rash, which usually clears up in a few days.

Don’t Dive In! Water Allergy

We all need water to survive, but some people get hives, or urticaria, from water. A water allergy, known as aquagenic urticaria, is one of a group of hive-related conditions known as physical urticarias. “Urticaria is the medical word for hives, which are red patches and wheals that appear on the skin and are very itchy,” says Dr. Ford. “Why some people get hives from water is not really known.” This is one of the very rare types of allergies. The hives and itching usually go away in 15 to 30 minutes, and antihistamines will relieve symptoms of water allergy.

A Problem if You Want to Get Pregnant: Semen Allergy

“This is an extremely rare type of allergy in women,” explains Ford. “In 30 years of practice, I have only seen it once.” Symptoms are hives and swelling in the vaginal area after sexual intercourse. Your doctor will do a skin test to make the diagnosis. The best treatment is to use a condom, but women who want to become pregnant can get allergy shots to treat semen allergy. If that doesn’t work, artificial insemination is an option.

On the Bench: Allergy to Exercise

This type of allergy has been reported in the medical literature only about 1,000 times since the 1970s. In mild cases, exercise allergy causes only urticaria, or hives, but in a more severe form, it can lead to anaphylaxis, a dangerous condition in which your blood pressure drops suddenly and you have trouble breathing. “There are two types of exercise allergy,” Ford says. “One type occurs after eating food and within two hours of exercise, and the other occurs without eating food. In either case, you should stop exercising, but you can prevent the food-related type by not eating before exercise.” Treatment of anaphylaxis, a medical emergency, may require injections of the drug epinephrine.

Solar Flare: Allergy to the Sun

“Solar urticaria is another of the physical urticarias,” explains Ford. “Symptoms are hives caused by sun exposure. The hives can be treated with antihistamines, and avoidance of sun can prevent this reaction.” Fortunately, sun allergy is very rare. When it happens, the hive symptoms, which include stinging and itching, appear within 30 minutes of sun exposure and clear up within minutes of getting out of the sun. The reaction seems to be caused by ultraviolet light. Antihistamines can relieve the reaction but not prevent it.