2023-06-20 12:57:21
If your skin touches a nettle, it gives a burning sensation. But how come?
The name ‘stinging nettle’ perfectly describes what happens when you touch it: it burns. That feeling is irritating, but usually disappears pretty quickly. What causes that burning sensation? If you look closely at the stem and leaves of a nettle, you will see a kind of hairs on it. They are there for protection. If you touch the nettle, the plant can be damaged. To protect itself against this, the tip of the hair falls off and a needle appears. These needles pierce your skin and introduce a chemical substance into your body, consisting of histamine, serotonin, acetylcholine and formic acid, among other things. The combination of these substances causes – it is not fully known – the bumps and itching.
Photo: Peter Westen
Angry outside world
The substance histamine is often mentioned when it comes to allergic reactions. It is a substance that also occurs in our body and is part of our defense mechanism against the big bad outside world, it is located in immune cells. If there is too much histamine in our body, for example due to a nettle sting, an allergic reaction occurs. Swelling and itching can occur, just like when you touch a nettle. Serotonin is mainly discussed in combination with depression. Too little serotonin in your body can make you feel unhappy, but it also seems to cause aggression. However, in combination with the other substances from the nettle needle, serotonin in the skin mainly causes irritation and pain.
Burns
Acetylcholine and formic acid – probably – also cause the burning sensation you get after coming into contact with the nettle. Pure formic acid is a particularly corrosive substance. If you get it on your skin in larger quantities than with the nettle, you can get severe burns. It is unclear which substances have the largest share in the nettle reaction. It is clear that many of these substances also occur in other poisonous plants or animals, such as jellyfish, bees and wasps.
Detail of a nettle. Photo: Evelyne Lapouge
What helps against the itch? Deadnettle!
If you have touched a stinging nettle, the irritation generally disappears after an hour or so. If you want it to go faster, you can put dead nettle on it. It often grows close to the nettle, and the plants look a bit alike. This phenomenon, in which a harmless animal or plant resembles another dangerous animal or plant, is called mimicry. The dead nettle has made good use of the fear that the nettle evokes in humans and animals. However, the difference between the dead nettle and the nettle is visible, although you have to look closely.
The stem of the dead nettle is almost square, while that of the nettle is more rounded. The deadnettle also has beautiful white lip-like flowers. The nettle has inconspicuous yellow-green flowers. By smearing the bumps of the nettle with leaf of the dead nettle, they disappear.
In the book Natural Biology by biologist Sara van Duijn you will find 69 other intriguing questions about plants, animals and people in addition to this question, such as ‘Do butterflies sleep?’ and ‘Why are there so many different types of clouds?’ Natural Biology, Sara van Duijn. Publisher Q, € 16.50.
Sara van Duijn answered this question in Roots: Do plants also have faeces?
More questions about nettles
Text: Sara van Duijn
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