Antihistamine
The vast majority of marketed H-antihistamines are receptor antagonists and only a minority of marketed compounds are inverse agonists at the receptor. Clinically, H-antihistamines are used to treat allergic reactions and mast cell-related disorders. Sedation is a common side effect of H-antihistamines that readily cross the blood–brain barrier; some of these drugs, such as diphenhydramine and doxylamine, are therefore used to treat insomnia. H-antihistamines can also reduce inflammation, since the expression of NF-κB, the transcription factor the regulates inflammatory processes, is promoted by both the receptor's constitutive activity and agonist (i.e., histamine) binding at the H receptor.
Cold urticaria
Allergy medications containing antihistamines such as diphenhydramine (Benadryl), cetirizine (Zyrtec), loratidine (Claritin), cyproheptadine (Periactin), and fexofenadine (Allegra) may be taken orally to prevent and relieve some of the hives (depending on the severity of the allergy). For those who have severe anaphylactic reactions, a prescribed medicine such as doxepin, which is taken daily, should help to prevent and/or lessen the likelihood of a reaction and thus, anaphylaxis. There are also topical antihistamine creams which are used to help relieve hives in other conditions, but there is not any documentation stating it will relieve hives induced by cold temperature.