Antihistamines are the formulations that block the receptors of histamine that cause an allergic answer of the organism. Histamine is a neurotransmitter that can impact the airways (bronchospasm), skin (itching, blister-hyperemia), digestive tract (intestinal colic, stimulation of gastric secretion), cardiovascular system (expansion of capillary vessels, increased vascular permeability, hypotension, cardiac arrhythmia), and smooth muscle.
Antihistamines are used to cope with allergy as well as for the reduction of cold and flu manifestations. There are three types of antihistamines and only H1-receptor blockers are used for allergy.
The most known medications from the group of antihistamines are cetrin (cetirizine), phencarol (hifenadine), diphenhydramine, clemastine, and suprastin. They are available in pill form, nasal spray, drops, including ophthalmic drops, solution for intramuscular administration (usually for emergency therapy).