From the Research
The triple response of Lewis is a physiological reaction that occurs when the skin is stroked firmly with a blunt object, consisting of three distinct phases: red line, flare, and wheal, with the most recent evidence suggesting that histamine release from mast cells plays a crucial role in this response 1. The initial red line appears due to direct capillary dilation from mechanical stimulation.
- This is followed by the flare, a reddening of surrounding skin caused by an axon reflex that releases vasodilators like substance P and calcitonin gene-related peptide from sensory nerve endings.
- The final phase is the wheal, a raised area resulting from increased vascular permeability and fluid leakage into surrounding tissues. This response involves histamine release from mast cells, activated by neuropeptides from sensory nerves, as supported by studies on the role of histamine in allergic diseases 2. The triple response is medically significant as it demonstrates normal neurogenic inflammation and vascular reactivity.
- Exaggerated responses may indicate dermatographism or urticaria, while diminished responses could suggest autonomic neuropathy or vascular dysfunction. No medications are typically needed as this is a normal physiological response, though antihistamines may reduce the reaction in hypersensitive individuals, as discussed in the context of mast cells and eosinophils in allergic inflammation 3. Understanding this response helps clinicians assess cutaneous vascular and neurological function in various clinical conditions, with recent studies highlighting the complex role of mast cells in allergy and inflammation 4.