Antihistamines are drugs that block the effects of a chemical called histamine. Produced by the body, histamine can cause symptoms such as itching, sneezing, runny nose and watery eyes. Antihistamines are used to treat skin conditions such as itchy rashes. They are particularly effective in treating hives. In addition, antihistamines are the most commonly used type of drug for the treatment of allergy symptoms.

Antihistamines are sold under a variety of generic and brand names, and are available in both over-the-counter and prescription form. Depending on the type of antihistamine, the drugs can be administered in several different forms, including:

• Topical creams
• Pills
• Liquid
• Nasal sprays
• Eye drops

Potential side effects of antihistamines include drowsiness, irritability and nightmares. Children and the elderly should be careful when using antihistamines because side effects can be more pronounced among these two groups.