of, relating to, or of the nature of preference: preferential policies. 2. showing or giving preference: a preferential hiring system. 3. receiving or enjoying preference, as a country in trade relations; favored. Origin of preferential.
Histamine dilates post-capillary venules, activates the endothelium, and increases blood vessel permeability. This leads to local edema (swelling), warmth, redness, and the attraction of other inflammatory cells to the site of release. It also depolarizes nerve endings (leading to itching or pain).
Histamine. Histamine is a chemical the immune system uses to help protect the body's cells against infection. The immune system is the body's natural defence against illness and infection. If the immune system detects a harmful foreign object, such as bacteria or a virus, it will release histamine into nearby cells.