Stinging nettle (Urtica dioica) greatly reduced pain and disability from osteoarthritis in a study at England’s University of Plymouth. Every day, twenty-seven brave souls applied the fresh leaves to their arthritic fingers and endured nettle’s characteristic sting caused by formic acid in its leaf hairs. This old folk remedy helped the study’s participants so much that they were able to reduce their use of analgesic and anti-inflammatory drugs. In fact, half of them preferred using nettles over standard pain relief medication. Eighty-five percent said they didn’t even mind the small welts that sometimes appeared. When the experiment was repeated five weeks later using white dead nettle (Lamium album) as a placebo (because it resembles stinging nettle), it did not produce the same results. Previous studies make researchers think that nettles reduce sensations of the pain pathway.
Source: Randall, C., et al. “Randomized controlled trial of nettle sting for treatment of base-of-thumb pain.” Journal of the Royal Society of Medicine 2000, 93(6): 305–309.