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 histamine increases blood flow to the area---ostensibly to bring in white cells to fight infection---which causes swelling. Histamine also causes fluid release, leading to runny nose and eyes, notes Dr. Sherwood. As mucus builds up in the nasal passages, it can irritate the throat, leading to soreness.