An allergy is the result of the body's immune system reacting to substances. The most common allergic conditions include hay fever, asthma, skin and food allergies. The basic cause of allergy is unknown. Allergies run in families, but there are other factors as well. For example, breast fed babies are less likely to have allergies than are bottle fed babies. It is not known why a person can become sensitive to some things and not to others.

Many substances are capable of causing an allergic reaction. The most common are pollen, mold, house dust, animal hair and dander, feathers, food, drugs, and insect stings. These allergens cause different kinds of allergic reactions. Pollen of trees, grasses, weeds, or molds cause hay fever. Hay fever symptoms include sneezing, itching and weeping eyes, stuffy or running nose, and cough.

Asthma results from a partial closing of the airways of the lungs. The main symptoms are wheezing and shortness of breath. Asthma attacks can be triggered by pollens, molds, house dust, exercise, infection, weather changes and stress.

Skin allergies, such as contact rashes like eczema, affect the skin. Contact with allergens like plants, nickel, and dyes can produce itchy rashes and weeping blisters. Hives are small, red, itchy inflamed swellings found in clusters on the skin.

Certain foods may cause allergic symptoms. Common ones include fish, eggs, milk, nuts, and wheat. Symptoms include diarrhea, hives, eczema, headaches, asthma, and a runny nose. Food allergies often occur in children, who usually outgrow it after age three.

Anaphylactic shock is the most serious kind of allergic reaction and is life threatening. It affects many areas of the body at the same time. It may be caused by insect venom, certain foods, and drugs such as penicillin. Within seconds or minutes, allergic shock affects breathing and circulation. If not treated right away, breathing may stop and death may occur.

Whatever the type of allergy, learning the cause can help in effectively avoiding or managing the symptoms.

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