Thetriple response of Lewis is a cutaneous response that occurs from firm stroking of theskin. This produces an initialred line, followed by a flare around that line, and then finally awheal.
The triple response consists of three aspects:
The red spot emerges within 15seconds.[4] Flare can take up to 45 seconds to begin.[4] Wheal can take up to 3minutes to begin.[4][5]
The triple response is caused by firm stroking of the skin with a pointed object.[5] but some time at caused by capillary vasodilation.[citation needed] The triple response of Lewis is particularly sensitive in people withdermatographia urticaria.[4][5] Some form of dermatographia is present in around 5% of the population.[4]
The triple response of Lewis is due to the release ofhistamine.Histamine, or 2-(imidazol-4-yl)ethanamine, is a dibasicvasoactiveamine that is located in most body tissues but is highly concentrated in the lungs, skin, and gastrointestinal tract. Histamine is asmall molecule, stored in granules ofmast cells andbasophils. Mast cells and basophils are the effector cells involved in the immediate hypersensitivity response. Found in tissues throughout the body, they are particularly associated with blood vessels and nerves, and are in proximity to surfaces that border the external environment.
The underlyingpathophysiology offrostbite is a combination of freezing, vascular insufficiency (constriction and occlusion) and damage due to inflammatory mediators. As extremities cool, the ‘hunting response of Lewis’ (alternating vasoconstriction and vasodilation) occurs, ending with vasoconstriction.[1]