Which acid is found in stinging nettles?

What’s in this mix of different chemicals that causes the sting? Whilst we still haven’t identified every single compound in the mixture, we have some idea. We used to think that the main component was formic acid, the same compound contained in ant venom. Whilst formic acid is certainly capable of causing a stinging sensation, and it is present in stinging nettles, it’s now thought that it’s present in too low a concentration to account for the extended pain of a stinging nettle sting.

Other chemicals contained in the stinging nettle venom, and the ones we now think are primarily responsible for the pain it induces, are histamine, acetylcholine, and serotonin. Serotonin, in particular, might sound familiar – it’s produced in our bodies, and sometimes referred to as the ‘happy hormone’, though it’s actually responsible for a number of other roles too. When injected by the stinging nettle, however, it functions as an irritant, leading to pain. Acetylcholine is another neurotransmitter that can accomplish a similar effect, and you might remember histamine from previous discussions of allergies, particularly hayfever. In the venom, histamine causes inflammation and pain.