Why do stinging nettles sting?
The stinging nettle is a herbaceous perennial, growing to 1-2 m tall in the summer and dying down to the ground in winter. It has very distinctively yellow, widely spreading roots. The soft green leaves are 3-15 cm long, with a strongly serrated margin, a cordate base and an acuminate tip. Both the leaves and the stems are covered with brittle, hollow, silky hairs that were thought to contain formic acid as a defence against grazing animals; but recent research has revealed the cause of the sting to be from three chemicals – a histamine to irritate the skin, acetylcholine to bring on a burning sensation and hydroxytryptamine to encourage the other two chemicals (Elliott 1997). Bare skin brushing up against a stinging nettle plant will break the delicate defensive hairs and release the trio of chemicals, usually resulting in a temporary and painful skin rash.
