Antihistamines are the most widely used medications to relieve or prevent symptoms of allergic rhinitis (hay fever). Some antihistamines may also be used to treat chronic urticaria (hives).
These medications reduce symptoms by preventing the effects of histamine—a chemical substance produced by the body during an allergic reaction.
Antihistamines are available as a liquid, tablet or nasal spray. Different antihistamines are available either by prescription or over-the-counter (OTC). Newer antihistamines prescribed by your allergist / immunologist are less likely to have side effects such as drowsiness, dry mouth, constipation or difficulty urinating.