Antihistamines

Antihistamines work by blocking the effect of histamine on the respiratory system. Histamine is a messenger substance that is released and causes inflammation and other allergy symptoms when your body is exposed to an allergen.

Antihistamines work best at reducing symptoms of itching, sneezing, and runny noses, as well as itchiness and inflammation of the eyes. However, antihistamines do little to reduce congestion of the nose.

There are two kinds of antihistamine medication--sedating and non-sedating--which are available in both oral form and nasal spray.