Antihistamines are the most common medicines used to treat allergies. Available as pills, liquids, nasal sprays and eye drops, they can be used by both children and adults. They block histamine, the chemical produced and released in allergic reactions that causes many of the symptoms of allergies and hay fever (allergic rhinitis).

Many antihistamines are also available combined with decongestants if significant congestion is a problem. Antihistamine/decongestant medicines are “behind” the counter but don’t require prescriptions.

People with seasonal allergies should start using antihistamines or nasal corticosteroids before the expected allergy period to get the best results. While some of these medications can relieve symptoms quickly, their long-term effectiveness builds up slowly. Starting medicine before an active pollen season can reduce most of the problems.

Nonsedating antihistamines may not cause drowsiness and sleepiness when used as directed, although drowsiness as a side effect varies.

Antihistamine eye drops relieve allergy symptoms such as itching, watery and red eyes. For people who experience a lot of eye symptoms along with their nasal allergies, eye drops can be very helpful when antihistamines or nasal corticosteroids are not sufficient. Some eye drops also contain mast-cell stabilizers for greater effectiveness.
Read more: When Allergy Medications Make You Drowsy