Stinging Nettle: The Chemical Needles
Woodland edges worldwide harbor plants with microscopic hypodermic needles. The stinging nettle covers its stems and leaves with hollow silicon-tipped hairs that break on contact. These inject a cocktail of histamine, acetylcholine, and formic acid under the skin. The resulting burn can last hours after a single touch. The plant evolved this defense against browsing animals and insects. Traditional medicine uses controlled exposure to nettle stings for treating arthritis through counter-irritation of painful joints.