Writing in the Journal of Emergency Medicine, the NHS Fife authors said leaf sap may be more important than the type of plant.
“If this were the case, any large, fresh, non-toxic leaf would be useful, and dock may have become favored simply because it grows in similar habitats to nettles,” the researchers wrote.
“Similar symptom relief may have occurred without any treatment at all, and our study design does not allow us to conclude that either dog food or lettuce is better than nothing.”
“I came to the conclusion that while dock leaf might be effective against nettle stings, lettuce might be just as effective, and either way it would provide immediate relief.”
Lettuce was chosen because it is similar in size, shape and texture to dock leaves but lacks the anti-inflammatory and toxic properties.
The dock-leaf cure cited by Chaucer
Nettle is a plant found widely in the British Isles. Its stems and leaves are covered in spines called trichomes that have brittle tips that break off when touched, spraying tiny amounts of chemicals onto the skin, including histamine, formic acid, acetylcholine, and serotonin.
Stings can cause a burning sensation, itching, white or red spots, or raised red spots that may take several days to go away.
Rubbing dock leaves on nettle stings was first mentioned 600 years ago in Geoffrey Chaucer’s Troilus and Criseyde, but there is little evidence that dock leaves contain any special properties that make them more beneficial than other plants.
It has been speculated that dock may contain natural antihistamines that reduce inflammation, but none have been found so far.
Similarly, it was once thought that the alkaline sap could neutralize the formic acid in the nettle, but it has since been found that dock sap is also acidic.
The pain-relieving effects of dock leaves are generally thought to be due to the cooling sensation felt as the sap evaporates and a placebo effect.
