Nettles have a peculiar notoriety.
The tiny spines along the stems and on the underside of the leaves are hardly noticed. But when touched, they release formic acid, the same chemical that lends authority to ant bites and bee stings. In a few seconds any skin that has touched the nettle begins to burn and sting. The stinging may last only a few minutes or as long as an hour. Several species of nettle from the warmer countries cause intense pain if carelessly handled.