histaminic

Very weak muscarinic and histaminic receptors antagonist.

Belladonna has been used in herbal medicine for centuries as a pain reliever, muscle relaxer, and anti-inflammatory, and to treat menstrual problems, peptic ulcer disease, histaminic reaction, and motion sickness.

Since you body produces histaminic reactions in reaction to cold organism invasions (or even histaminic reactions to irritan (sorry irritants) like the oil in poison ivy, the ANTI-histamine benedryl acts to lessen or reverse the histaminic reaction.