Antihistamines and decongestants. Your pediatrician or allergist may start with an over-the-counter medication combining an antihistamine (which blocks the release of misery-inducing histamine) and a decongestant (which shrinks nasal tissues to reduce congestion).

Many antihistamines cause drowsiness -- which could affect your child's schoolwork and social life -- as well as dry mouth or constipation. Nondrowsy prescription antihistamines are available for most children.

Nasal sprays. Simple over-the-counter saline solutions can work fine as decongestants and have no side effects. Sprays with cromolyn sodium (such as Nasalcrom for Children) relieve inflammation without the drowsy side effects of antihistamines. These must be used at least three times a day for several months prior to your child's allergy season.

Other prescription sprays containing corticosteroids (such as Flonase and Rhinocort) also reduce inflammation in the nose. But some experts caution that long-term use of inhaled corticosteroids can cause growth retardation in some children.

Allergy shots. If medicines and staying clear of allergens are not enough, immunotherapy regimes exist for ragweed, grass pollens, dust mites, some molds, and cat and dog dander.

As with common childhood-disease vaccines, an allergist injects minute quantities of the allergen your child is sensitive to under his skin, which helps the immune system become desensitized to it. Your child will have to go to the allergist at least once a week in the beginning, and then once a month for several years after that.

Children younger than age 5 generally don't get allergy shots, since many allergists fear their immune systems aren't strong enough to withstand the introduction of an allergen. But older children are good candidates for the treatment, and the best results for allergy shots are generally in the age 5 to 25 age group.