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).
Reaction of histamine. When you have a wound, your body cells are triggered to heal it by forming new tissues. These cells release a substance called histamine whenever they get a signal that your body has faced some trauma. This substance can cause an allergic reaction that you might experience in the form of itching.