Stinging nettle

Stinging nettles ("Urtica dioica") are a type of plant which have stinging defensive hairs on the leaves and stems. Stinging nettles can be found in America, Europe and Asia. 
Sting mechanism.
The hairs inject histamine and other chemicals that produce a stinging sensation when contacted by humans and other animals. Soaking stinging nettles in water or cooking removes the stinging chemicals from the plant, which allows them to be handled and eaten without injury. 
Usage.
The plant has been used as medicine, food, tea and fibre. Nettles are sometimes used in cheesemaking, as nettle soup or as substitute for spinach. Its stems contain a bast fibre that is used for the same purposes as linen. Nettles have been used to make clothing for 2,000 years.
Ecology.
Stinging nettles are important food plants for several butterflies, like the peacock butterfly and the small tortoiseshell. Also some deers and other animals eat the plant, preferred the leaf shot.