Antihistamines are most often used to treat the symptoms of allergies, particularly hay fever, and reactions to bites and stings. Taken in tablet form for hay fever and other allergies, antihistamines reduce itching of the nose and eyes, a runny nose and watering eyes, and sneezing. They are not as effective at unblocking a stuffy nose, but can be combined with a decongestant (a drug that reduces swelling in the mucous membranes and stops mucous being produced) to treat nasal congestion. In this combined form they are sometimes used to treat the nasal symptoms of the common cold. Oral antihistamines are also used for allergies to medicines (such as aspirin), to prevent and treat migraine symptoms, and to relieve severe morning sickness. You can also take antihistamine tablets containing drugs such as cyclizine or cinnarizine to prevent travel or motion sickness. Topical antihistamines are creams and ointments, applied to the skin. Antihistamine creams and tablets are both effective in reducing urticaria (hives or nettle rash), the itchy white bumps on the skin often caused by insect bites and stings. Oral antihistamines are also used to treat chronic (long-lasting) urticaria. Eyedrops containing antihistamines such as antazoline can be applied to the eyes, to treat allergic conjunctivitis (swelling and irritation of part of the eye). Injections of antihistamines such as chlorphenamine are used after adrenaline injections, in emergency treatment of serious allergic reactions such as anaphylactic shock and angioedema.
