Types of Allergens

Allergies affect approximately 50 million people in the United States, according to the Everyday Health website. Allergies vary by type of allergen and severity of symptoms, which may be instantaneous or develop gradually over time. An allergy is a physical reaction, such as watery eyes or sneezing, that occurs when the body's immune system reacts to a specific foreign particle, known as an allergen. Allergens can take many forms, both common and uncommon -- for example, particles as in pollen and mold allergies or chemicals as in food allergies.

Pollen

• Pollen, which causes allergic rhinitis, more commonly known as hayfever, is a microscopic particle formed by trees, grasses and weeds and is spread by the wind. Flowers also produce pollen; however the likelihood of developing an allergic reaction to flower pollen is low because flowers produce heavy, waxy pollen that is unlikely to be spread by the wind. The pollen season normally begins with the start of spring, but can start as early as January and lasts through October.

Animal Dander

• A common misconception is that allergies to animals are caused their fur. In reality, animal allergies are caused by proteins from animal saliva or skin oils that are carried through the air by the animal's dander. Dander is loose skin cells that may float in the air and trigger an allergic reaction. Although severe allergies do exist, animal allergies, mainly caused by cats and dogs, are mostly mild in symptoms such as watery, itchy eyes and sneezing.

Dust Mites

• Dust mites are tiny, eight-legged creatures in the arachnid family that live in homes, hotels and other places that provide the proper environment. Dust mites can be seen only through a microscope, but are known to live in carpets, bedding, furniture and stuffed animals. Dust mites do not bite or spread disease; they eat flakes of dead skin which slough off of us regularly. The allergy to dust mites is not caused by the insect itself, but by the insect's droppings, and is often mild. It is virtually impossible to eliminate dust mites from your home, but you can lessen the allergy by frequently vacuuming carpets and furniture and washing linens and soft toys.

Foods

• It is important to understand that a food allergy is different than food intolerance -- an allergy involves the immune system while intolerance causes mainly gastrointestinal symptoms. In order to have a food allergy, you must first have been exposed to the food either firsthand or through breast milk. It takes minute amounts of a food, so little that it may not be visible, to trigger an allergic reaction. Symptoms can range from slight to life-threatening. About 90 percent of all food allergies are caused by milk, eggs, wheat, soy, tree nuts or peanuts.

Insect Stings

• Allergic reactions to insect stings are most common with bees, wasps, hornets, yellow jackets and fire ants. Most reactions last 2 to 3 hours and result in redness, swelling, itching and pain. Some people may have very severe reactions to stings resulting in severe symptoms such as difficulty breathing, low blood pressure, shock, loss of consciousness and even death.

Latex

• The diagnosis of latex allergies is on the rise as a result of latex's common use in products, especially those in the medical field. Sensitivity to latex rubber can be seen after contact with the skin, blood or mucus membranes. The allergy can also be triggered by blowing up latex balloons. Generally, latex allergy symptoms are mild, including swelling, itching and rash, but they can worsen with exposure and may become severe, reports the Children's Hospital of Pittsburgh.

Mold

• Mold, or fungus, is as green, black or white growths on damp surfaces such as soil, dead leaves, basement or bathroom walls, refrigerators or window sills. According to Lucile Packard Children's Hospital, molds usually contain spores, which are tiny round particles that can float in the air much like pollen and trigger allergic reactions. Mold allergies can be also be triggered by ingesting certain foods such as cheeses processed using fungi, mushrooms, yeasts, soy sauce, vinegar and dried fruits.

Poison Ivy, Oak and Sumac

• Poison Ivy is a term that can collectively refer to the native American plants poison ivy, poison sumac or poison oak. These plants contain urushiol, an oil in the plant's resin. Urushiol is effortlessly transferred to skin, clothing, animals and any other item that comes into contact with the plant and can remain active for more than a year. The oils can also be spread as an airborne particle in the smoke of burning plants. Symptoms may manifest as long as weeks after exposure and include dermatitis, rash, blisters, itching and swelling.