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).
The message is, Release histamines, which are stored in the mast cells. When they leave the mast cells, histamines boost blood flow in the area of your body the allergen affected. This causes inflammation, which lets other chemicals from your immune system step in to do repair work. Histamines then dock at special places called receptors in your body.