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. 

This answer was adapted from Sharecare's award-winning AskMD app. Start a consultation now to find out what's causing your symptoms, learn how to manage a condition, or find a doctor. 

Continue Learning about Nasal Agent

What is an antihistamine?
Jumo HealthJumo Health
Antihistamines are medicines that treat mild allergic reactions. Antihistamines come in tablets and ...
More Answers
How can I explain anesthesia to a child?
Rocky Mountain Hospital for Children at P/SLRocky Mountain Hospital for Children at P/SL
Children may have concerns about anesthesia before surgery. You can explain to them that there are n...
More Answers
Can decongestants relieve allergy symptoms?
If a stuffy, blocked-up nose is your primary allergy symptom, a decongestant may offer relief. These...
More Answers
What other medications do oral antihistamines interact with?
Donna Hill Howes, RNDonna Hill Howes, RN
If you are taking an opioid, antihistamines may not be good options for you. If you are taking a dr...
More Answers

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.