• Erythema: Superficial reddening of the skin as a result of relaxation of the blood capillaries from injury or irritation.
• Edema: Abnormal collection of fluid in the cavities or tissues of the body.
• Dermis: The layer of skin below the epidermis containing blood capillaries, nerve endings, sweat glands, hair follicles and other structures.
• Epidermis: The outermost layer of skin overlying the dermis.
• Pruritus: Severe itching of the skin.
• Angioedema: An abnormal swelling of the deeper layers of the skin usually caused by an allergic reaction.
• Histamine: A specific chemical released by the cells in response to injury or in allergic or inflammatory reactions that causes contractions of smooth muscles and relaxation of the capillaries.