![Urtica dioica trichomes [CC-BY-SA-3.0 Frank Vincentz]](https://www.polypompholyx.com/wp-content/uploads/2014/07/Urtica_dioica_trichomes-300x262.jpg)
Nettles have a rather unhappy reputation as bringer of painful welts, and – at this time of year – dribbling noses too. The welts are probably caused by histamine, and the pain by oxalic and tartaric acids, which the nettle injects into your skin through the tiny brittle hairs that cover its stems and leaves. If …