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).
In humans, the highest histamine concentrations are found in the skin, lung, and stomach, with smaller amounts in the brain and heart. Histamine is also essential in defending the body against invasion by potentially disease-causing agents such as bacteria, viruses and other foreign bodies.