Allergies:

Your immune system protects you from diseases by fighting germs like bacteria and viruses, but when you have allergies, it overreacts and tries to "fight" ordinary things like grass, pollen, or certain foods. This causes the sneezing, itching, and other reactions that you get with allergies.

The substances that cause allergies (grass, pollen, foods, pet by-products, insects, etc.) are called allergens. When your immune system reacts to one of these allergens and you have symptoms, you are allergic to it.

Some common allergens include:

• dust mites
• protein found in the dander, saliva, urine, or other things from some animals
• grass, flower, and tree pollen
• mold and mildew
• foods, such as milk, wheat, soy, eggs, nuts, seafood, and legumes, which include peas, beans, and peanuts
• latex

Some of these allergens cause sneezing, a runny nose, itchy eyes and ears, and a sore throat.

Other items on the list, such as foods, may cause hives (a red, bumpy, itchy skin rash), a stuffy nose, stomach cramps, vomiting, or diarrhea. Less often, allergens can cause breathing problems like wheezing and shortness of breath (asthma).

Some allergens, such as foods, are a problem all year long. But others might bother people only during certain seasons. For instance, you might be allergic to pollen from trees, which is present in the air only in the spring.

• Allergy Information
  Allergy information and resources.