What are antihistamines?

Some articles on antihistamines, antihistamine:

H1 Antagonist - Clinical Use of H1-antihistamines - Indications
... H1-antihistamines are clinically used in the treatment of histamine-mediated allergic conditions ... reactions—adjunct only Nausea and vomiting (first-generation H1-antihistamines) Sedation (first-generation H1-antihistamines) H1-antihistamines can be administered topically (thr ... recommend that, for cough associated with the common cold, first-generation antihistamine-decongestants are more effective than newer, non-sedating ...
Chlorphenamine
... is a first-generation alkylamine antihistamine used in the prevention of the symptoms of allergic conditions such as rhinitis and urticaria ... effects are relatively weak compared to other first-generation antihistamines ... Chlorphenamine is one of the most commonly used antihistamines in small-animal veterinary practice as well ...
Clemastine - Pharmacology
... Clemastine is an antihistamine with anticholinergic and sedative effects ... Antihistamines competitively bind to histamine receptor sites, thus reducing the neurotransmitter's effects ... Effects of histamine (which are countered by antihistamines) include Increased capillary permeability Increased capillary dilatation Edema (i.e ...
Histamine Antagonist - Clinical: H1- and H2-receptor Antagonists - H1-receptor Antagonists
... In common use, the term antihistamine refers only to H1 antagonists, also known as H1 antihistamines ... It has been discovered that these H1-antihistamines are actually inverse agonists at the histamine H1-receptor, rather than antagonists per se ... However, second-generation antihistamines do not cross the blood–brain barrier, and as such do not cause drowsiness ...
Chronic Urticaria - Management - Antihistamines
... Antihistamines such as diphenhydramine may be used ... The benefit of H2 receptor antagonists such as ranitidine is poorly supported by the evidence ...