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).
1 Much of the histamine in the body is produced by the granules in mast cells and basophils as part of a local immune response to the presence of invading bodies. Histamine is also made in the brain where it acts as a neurotransmitter or chemical messenger that carries signals between nerves. 2  Another important site where histamine is stored and released is in the enterochromaffin-like (ECL) cells of the stomach.