From a young age we were taught that the treatment for a nettle sting was to rub it with a dock leaf. Conveniently, docks usually grow close to where there are nettles.
- Does this actually do something to help?
- Is the effect entirely/mostly placebotic?
- How does it work? (and what is the best technique to use)
- Would washing/rubbing with water be as/more effective?
As an adult if I get stung I have used the same treatment. It does seem to gradually calm the sting but it is difficult to say if the sting would be better without the treatment.
The treatment especially seems to help kids. Looking around for dock leaves is a great distraction. Kids are really happy to be able to help and do something about the problem. I have also heard that getting stung with a nettle is "lucky" (think magic fairy type of lucky here - woo!) and also that it gives a boost to the immune system (now that sounds much more scientific!). These two things are another good distraction and comfort to kids especially.
Physical action ?
Does rubbing the sting with juice of dock leaf simple rub away the sting needles? And does the juice dilute the chemicals injected in the sting?
In the summer when the nettles are out and it is common to get stung I have found several times that no water is convenient (even in Ireland) so the best source of something cooling is a crushed dock leaf.
Chemical action ?
I believed nettles had an acid in the sting and that dock leaves had a base. And a simple acid+base=>salt+water neturalising reaction took place to calm the sting.
However, reading a bit more about this shows up different and sometimes contradictory information. It is hard to determine what are actual facts. What chemicals are involved depend on what article you are reading!
I think the facts on nettle sting are: Stinging nettles have sharp needles of silica(glass). There is a mix of chemicals which are injected by the needles. From wikipedia : several chemicals: acetylcholine, histamine, 5-HT (serotonin), moroidin, leukotrienes, and possibly formic acid.
- Stinging Nettle: https://en.wikipedia.org/wiki/Urtica_dioica
Doc leaves are related to sorrel (and related to rhubarb). The leaves contain oxalic acid and tannins. It is also said they contains an antihistamine.