Many types of nettles protect themselves from herbivores with stinging hairs located on all parts of the plant. Each hair is a large cell, shaped like a medical ampoule. The upper part of the "ampulla" protrudes beyond the surrounding cells of the outer surface of the plant. This tip contains silicon salts. Even with a slight impact, the tip breaks, the sharp end penetrates the skin, and the contents of the cell enter the animal's body. Cell sap contains histamine, choline and formic acid, the effect of which is manifested by the sensation of a sharp "burn" at the point of touching the plant.Most stinging nettle burns are relatively harmless, but several tropical species are known to be very painful and even fatal to touch (Urtica ferox, a nettle tree from New Zealand).
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