Allergies happen when your body's defense system overreacts to a foreign substance, called an allergen; an estimated 40 to 50 million Americans have allergies. We're all familiar with the more common allergens – animal dander, food, pollen, dust, and mold – and you're probably allergic to one or more of them yourself. But it may surprise you to learn that you can develop allergies to all kinds of odd things. Here are a few.
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.
Myth or Reality: Allergy to Electricity
People who claim to suffer from electrosensitivity say they are sensitive to electricical fields generated by products such as cell phones, microwaves, computers, and power lines. Symptoms of electricity allergy include headache, ringing in the ears, fatigue, and many other complaints. This is one type of allergy you probably do not have to worry about, says Ford, because there is "no such thing." There have actually been several studies done to see if electrosensitivity exists, and almost all of the studies have come up empty.
Plastic, Please: Allergy to Coins
If you get an allergic rash on your hands after handling coins, you could have another type of contact dermatitis — a reaction to nickel, one of the metals from which coins are made. Nickel is a silvery metal that is mixed with other metals to form alloys. It's found in coins, jewelry, zippers, the frames of eyeglasses, and many other products, and if you're sensitive to it, you can develop a rash wherever nickel comes in contact with your skin. As with other allergens that cause contact dermatitis, the best treatment is to avoid the substance, take antihistamines after exposure, and perhaps apply a topical steroid cream when a rash develops.
Written on Your Skin: Touch Allergy
Dermographism is yet another type of physical urticaria. The word means "skin writing," and the condition is so named because if you have this type of allergy you can write your name on your skin with pressure from your fingernail. Pressure on the skin causes an itchy hive reaction. You can also develop this urticaria rash from tight clothing or even just toweling off after a hot shower. Dermographism affects about 4 percent of the population. The rash goes away on its own in about 15 to 30 minutes. You can use antihistamines to control the itching it causes.
Beyond Brrr: Allergy to Cold
Cold urticaria, another of the physical urticarias, is very rare, but potentially dangerous. "Cold urticaria can be life-threatening if a person is suddenly exposed to extreme cold, such as diving into very cold water. This can cause a massive release of histamine, which can severely drop the blood pressure," notes Ford. Managing this type of allergy centers on prevention — avoiding exposure of large areas of skin to the cold and never swimming alone.
Eat Veggies Instead: Allergy to Pollinated Fruit
If you are one of the millions of Americans who have pollen allergies, you could experience a type of allergy known as oral allergy syndrome. "This allergy occurs when someone is allergic to pollen and then eats a fruit that contains the same protein as the pollen," explains Ford. This is called cross reactivity, and it can occur between ragweed and bananas, grasses and tomato, and birch trees and apples, plums, or peaches. Symptoms of such allergies are an itchy mouth and throat, and sometimes swelling of the lips. Symptoms usually go away if you swallow or spit out the fruit, and treatment is usually not necessary.
- Last Updated: 11/24/14