Etymology
Urtica is derived from a Latin word meaning sting.Dioica (δίοικος) is derived from Greek, meaning of two houses (having separate staminate and pistillate plants; dioecious). Distribution and habitat
U. dioica is considered to be native to Europe, much of temperate Asia and western North Africa. It is abundant in northern Europe and much of Asia, usually found in the countryside. It is less widespread in southern Europe and north Africa, where it is restricted by its need for moist soil, but is still common. It has been introduced to many other parts of the world. In North America, it is widely distributed in Canada and the United States, where it is found in every province and state except for Hawaii, and also can be found in northernmost Mexico. It grows in abundance in the Pacific Northwest, especially in places where annual rainfall is high. The European subspecies has been introduced into Australia, North America and South America.In Europe, nettles have a strong association with human habitation and buildings. The presence of nettles may indicate the site of a long-abandoned building, and can also indicate soil fertility. Human and animal waste may be responsible for elevated levels of phosphate and nitrogen in the soil, providing an ideal environment for nettles. Ecology
Nettles are the larval food plant for several species of butterflies, such as the peacock butterfly, comma (Polygonia c-album), and the small tortoiseshell.
Demodicosis , also called Demodex folliculitis in humans and demodectic mange () or red mange in animals, is caused by a sensitivity to and overpopulation of Demodex spp. as the hosts immune system is unable to keep the mites under control. Demodex is a genus of mite in the family Demodecidae. The mites are specific to their hosts, and each mammal species is host to one or two unique species of Demodex mites. Therefore, demodicosis cannot be transferred across species and has no zoonotic potential. Signs and symptoms
Humans
Demodicosis in humans is usually caused by Demodex folliculorum and may have a rosacea-like appearance. Common symptoms include hair loss, itching, and inflammation. An association with pityriasis folliculorum has also been described.Demodicosis is most often seen in folliculitis (inflammation of the hair follicles of the skin). Depending on the location, it may result in small pustules (pimples) at the base of a hair shaft on inflamed, congested skin. Demodicosis may also cause itching, swelling, and erythema of the eyelid margins. Scales at the base of the eyelashes may develop. Typically, patients complain of eyestrain. Dogs
Minor cases of demodectic mange usually do not cause much itching but might cause pustules, redness, scaling, leathery skin, hair loss, skin that is warm to the touch, or any combination of these. It most commonly appears first on the face, around the eyes, or at the corners of the mouth, and on the forelimbs and paws. It may be misdiagnosed as a "hot spot" or other skin ailment.