|Histamines are responsible for many of the symptoms of allergies and allergic reactions, including nasal congestion, itching, watery eyes, and hives. Antihistamines act by blocking histamine receptors, so that the histamines can not cause a reaction.
While effective for a runny nose, sneezing, and nasal itch that is caused by allergies, the nasal congestion that is part of an upper respiratory infection is not related to histamine, and so these medicines are not very effective. It is the side effects of the antihistamines that can make them useful in upper respiratory illnesses, including causing drowsiness and a dry mouth and nose.
Antihistamines also do not help congestion, so if your child mostly has a stuffy nose or is congested, a decongestant and/or a nasal steroid may be a good alternative.
Common antihistamines include:
- diphenhydramine (Benadryl)
- brompheniramine (Dimetapp, Bromfed), chorpheniramine (Chor-trimeton, Pediacare, Naldecon, Rynatan, Triaminic), triprolidine (Actifed) , pyrilamine, clemastine (Tavist), and carbinoxamine (Rondec). These are usually a part of multisymptom cold relievers.
- cyproheptadine (Periactin). A long acting prescription antihistamine, sometimes used for prophylaxis for frequent migraines and recurrent abdominal pain.
- hydroxyzine (Atarax or Vistaril). A long acting prescription antihistamine.
- loratadine (Claritin), desloratadine (Clarinex), cetirizine (Zyrtec), levocetirizine (Xyzal), and fexofenadine (Allegra) are newer, second generation antihistamines that are available by prescription to treat allergies and are usually less sedating than older medications.