I'm Gwen Outen with the VOA Special English Health Report.

An allergy is an unusually strong reaction to a substance. Many different things can cause allergies. The most common cause is pollen. Trees and many other kinds of plants release pollen into the air to reproduce successfully.

Different kinds of plants produce pollen at different times of the year. For example, trees usually produce pollen in the spring, grasses pollinate in the summer. Weeds produce pollen in the autumn.

Many other things can cause allergies. They include organisms such as dust mites and molds, dead skin particles on dogs and cats, chemicals, plants, medicines and some common foods. Insect bites also can cause allergic reactions.

There are several kinds of allergic reactions. The most common reaction is watery, itchy eyes and a blocked or watery nose. Other reactions include red, painful, itchy skin. Some allergic reactions can be life threatening. For example, allergic reactions that block breathing tubes are very dangerous.

Doctors say there are several ways to treat allergies. They say people should try to avoid the substances that cause allergic reactions. Medicines called antihistamines are used to treat allergies.

Another treatment is called immunotherapy. This involves injecting a patient with small amounts of the allergy causing substances. Larger and larger amounts are given. Overtime, the patient develops a resistance to the allergy causing substance.

This treatment is usually effective against allergies to small particles in the air, like pollen or dust and insect bites. However, this treatment is generally not used for allergies to foods. In some cases, they can be life-threatening reactions.

The National Institute of Allergy and Infectious Diseases says four percent of Americans have severe food allergies. On June 24th, the institute announced a new food allergy research group. Plants call for 22 million dollars to be spent over five years.

Scientists will look for new ways to treat and prevent food allergies. Studies will take place at five research centers. The first project will involve testing experimental new treatments for allergies to peanuts. The second project will involve a study of 400 babies with allergies to milk or eggs.

This VOA Special English Health Report was written by Mario Ritter. Our reports are on the Web at voaspecialenglish.com. I'm Gwen Outen.

allergy: an abnormally high sensitivity to certain substances, such as pollens, foods, or microorganisms. Common indications of allergy may include sneezing, itching, and skin rashes（敏感癥，過敏性反應）

pollen : the fine, powderlike material consisting of pollen grains that is produced by the anthers of seed plants（花粉）

pollinate: to transfer pollen from an anther to the stigma of (a flower)（傳花粉給；授以花粉）

mold: any of various fungi that often cause disintegration of organic matter（真菌，霉菌）

immunotherapy: treatment of disease by inducing, enhancing, or suppressing an immune response（免疫療法，通過誘發(fā)、增強或抑制免疫反應的療法）