Histamine is commonly known as the dreaded mediator of allergic reactions and hypersensitivities. A special type of cell, called the mast cell, plays the key-role in these inflammatory events. The mast cell is a connective tissue cell that contains several inflammatory mediators in their inactive state. When mast cells are triggered,
such as by free radicals or during an allergic reaction, they degranulate and release inflammatory mediators such as histamine, serotonin, and bradykinin. During degranulation, mast cells also release an enzyme called hyaluronidase. Its task in the mast cell is to activate histamine during the degranulation.
Mast cells are present throughout the body, so at any given time and place they can instantly liberate their agents to initiate the inflammatory response.

Allergic reactions, sensitivities and inflammations can flare up anywhere in the body and result in numerous health problems and disorders. The inflammatory process manifests itself in skin diseases such as eczema, nettle rash, psoriasis, sunburn, and itching; in respiratory disorders including bronchitis, asthma, cough, and hay fever; in joint problems such as rheumatism; and in stomach ulcers and after hemorrhages. In all these events, the free radical scavenging effect of OPCs checks oxidative stress, which precedes and accompanies any inflammation.