Do All Nettles Sting? Species Differences and the Chemistry of the Sting

Only some nettle species have stinging trichomes. Stinging nettles (Urtica dioica, U. urens, U. chamaedryoides) inject histamine, acetylcholine, serotonin, and formic acid via fragile silica‑tipped hairs, causing urticaria. Non‑stinging nettles (e.g., dead nettle, Lamium purpureum) lack these trichomes and are harmless—often used as ornamental ground cover.