In the pharmacodynamics term, Antihistamines usually competes with Histamine H1 receptors or H2 receptors in the cell membrane.
Most of the Antihistamines bind to other receptors therefore it applies to other pharmacologic actions. The mast cells and basophils are the main sources of Histamine, and its basic uses of Antihistamines in diseases made by excessive production and the release of Histamine from these two types of cells. In experimental trials, it has been proven to be of use in evaluation of Antihistamines content in humans. In the case of the central nervous system, sadly, the models are not available and in other means which must also be devised. The duration of oral route and dose response Antihistamines can be defined by a single skin model by blocking the wheal and erythema which might result in an intradermal obstacle with Histamine and allergen. Antihistamines can be evaluated in urticaria induce from scratching or cold.
Injection of Histamines into the skin is for itching, it is usually inhibited by this type of class drugs. The commonly used Antihistamines are effective which is used to treat skin diseases. There are other methods like injection in the nose and conjunctiva are used.