Many kids have allergies — in fact, they're the most common cause of chronic nasal congestion in children.

Allergen immunotherapy (allergy shots) can be an effective treatment for allergies. Here are the basics on allergy shots and how to help a child deal with them.

Why Allergy Shots Are Used

An allergy occurs when the body's immune system has an exaggerated reaction to a usually harmless substance. The most common allergens (substances that trigger the allergy) are dust mites, molds, pollen, pets with fur or feathers, stinging insects, and some kinds of foods.

The body reacts to the trigger by releasing chemicals, one of which is histamine. Allergic symptoms can include runny nose, congestion, sneezing, itchy eyes, and ear itching or popping. Asthma also might occur in some kids.

The best way to prevent or control allergy symptoms is to avoid triggers. An allergist (a doctor trained to identify and treat allergies) will look for causes of an allergy by testing a person's reaction to specific allergens with skin or blood tests. Then, based on the test results, the allergist or another doctor can recommend treatments, including medications and ways to avoid exposure to allergens.

If environmental control measures and treatment with basic allergy medications are not successful, allergy shots might be recommended as the next step.