Giving In To The Urge To Scratch: Researchers Find Not All Itches Created Equal

... Different reactions in the brain to two common allergy triggers -- allergens (pollen and dust) and histamine (allergy cells within the body caused by foods, drugs or infection) -- may shed some light on the itch-scratch cycle. Allergen-induced itch intensity ratings were higher compared to histamine and perception of itch and changes in blood flow were significantly greater when allergen induced. Itch intensity and changes in blood flow were perceived to exist for significantly longer periods. ...