Scleritis (inflammation of sclera) is a strong indication of the underlying medical problem. It can be due to fungal, viral or parasitic infection, trauma, exposure to chemicals, poisonous gases or due to post-surgical complications.
Mast cells are granulated cells typically found in connective tissue. These cells mediate immune responses to foreign particles. In particular, they release large amounts of histamine and enzymes in response to antigen recognition.
Histamine is also the irritating ingredient present in the venom of many species of wasps and bees. In humans histamine is found in nearly all tissues of the body, where it is stored primarily in the granules of tissue mast cells. The blood cells called basophils also harbour histamine-containing granules.