Antihistamines are the most commonly used type of drug for the treatment of allergy symptoms. The drugs work by blocking the effects of a chemical called histamine, which is released into the bloodstream during allergic reactions.

By using an antihistamine, an individual is able to reduce many of the symptoms commonly associated with allergies, including runny nose, watery eyes, itchiness and an irritated throat. Antihistamines are also used in some cases to treat motion sickness, sleeplessness and even Parkinson’s disease.

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 through several different methods, including:

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

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

Pregnant mothers can generally take one category of antihistamine – known as category B – with a very low risk of complications, though they should always contact a physician before taking any type of medication.