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 is primarily: (2) 1  A neurotransmitter, like a chemical messenger, that passes from one neuron to another in the nervous system. 2  A component of stomach acid that helps break down food.  An inflammatory response mechanism that dilates blood vessels to enable white cells to quickly reach and neutralize invaders.