What are oral antihistamines?

The most commonly used oral antihistamines are second generation antihistamines such as loratidine (Claritin ), cetirizine (Zyrtec) and fexofenadine (Allegra). These antihistamines are less sedating than older first generation antihistamines such as Benadryl. They are also available combined with a decongestant, most commonly pseudoephedrine.

Donna Hill Howes, RN
Family Practitioner

Histamine is a chemical produced by the body. It is a normal part of the body's immune system and its defense against germs, such as bacteria and viruses. People with nasal allergies produce too much histamine in response to common irritants, such as pollen and mold. This causes the usual symptoms of runny nose and itchy eyes. An antihistamine is a drug that blocks the action of histamine.

Many oral antihistamines (those taken by mouth) are available in the US. Newer ones include cetirizine (Zyrtec), desloratadine (Clarinex), fexofenadine (Allegra), levocetirizine (Xyzal), and loratadine (Claritin). Some of these, such as desloratadine and levocetirizine, require a prescription. Others are available over the counter. Many other products combine an antihistamine with another drug such as a decongestant in a single pill. 

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