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 a chemical involved in your immune system, proper digestion, and your central nervous system. As a neurotransmitter, it communicates important messages from your body to your brain. It is also a component of stomach acid, which is what helps you break down food in your stomach. You might be most familiar with histamine as it relates to the immune system.