Why do nettle stings hurt?

THAT'S THE WHY:IF YOUR skin has ever brushed against the surface of a stinging nettle, you'll know the sudden burning sensation you feel on contact. But what is it about Urtica dioica that makes it such a pain?

The stinging nettle is an upright perennial with characteristic jagged leaves, and it tends to crop up in woodland and disturbed areas.

From a safe distance the plant looks harmless enough, but if you get right up close and analyse the leaves using a microscope, the reasons for the nettle’s kick become clear.

Stinging hairs dot the surface of the leaves and protrude as tiny hollow spines fill with silica, each with a bulb at its base that contains a number of different chemicals with biological properties.

When the silica rods break on contact with something like your bare hand or leg, their sharp ends can pierce the skin and a payload of serotonin, acetylcholine and histamine are released from the bulb, causing pain and triggering a local, inflammatory reaction.

Formic acid released by the nettle may also contribute to the sting, but as the acid is released in such small quantities, its role is unclear.

If left untreated, nettle stings can hurt for up to several hours and red welts or itchy rashes can appear on the skin at points of contact.

Reported soothing agents that can be applied topically (and gently to avoid further irritation) include anti-histamine creams, baking soda paste and the juice of Rumex (dock) leaves.

– CLAIRE O’CONNELL