hydatid

an itchy rash resulting from the release of HISTAMINE by MAST CELL . Individual swellings (weals) appear rapidly and resolve spontaneously within hours. Acute urticaria is common and represents an immediate response to such allergens as seafood or strawberries. Chronic urticaria is not an allergic condition and may persist for years. Angio-oedema occurs when the weals involve the lips, eyes, or tongue, which may swell alarmingly and constitute a medical emergency. URTICARIA can be prevented by taking antihistamines regularly. Cholinergic urticaria is a condition in which very small weals are brought on by heat, exercise, or emotion; treatment may be with hydroxyzine or ketotifen.