Skin layers: epidermis, dermis, and subcutis, showing a hair follicle, sweat gland & sebaceous gland. In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs.[1] Skin pigmentation (see: human skin color or coloring) varies among populations, and skin type can range from dry skin to oily skin. The adjective cutaneous literally means "of the skin" (from Latin cutis, skin). As the interface with the surroundings, skin plays the most important role in protecting (the body) against pathogens. Its other main functions are insulation and temperature regulation, sensation, and synthesis of vitamin D and the protection of vitamin B folates. Severely damaged skin will try to heal by forming scar tissue, often giving rise to discoloration and depigmentation of the skin. The use of natural or synthetic cosmetics to treat the appearance of the face and condition of the skin (such as pore control and black head cleansing) is common among many cultures. Oily skin is caused by hormonal fluctuations in the body, which lead to a DHT sensitivity. This sensitivity means that the skin begins to lose moisture and essential fatty acids (linoleic acid in particular), causing thousands of skin cells to die, so the skin compensates for this loss of moisture by producing higher levels of oil.[2] Oily skin can be cleaned quickly with a mild solution of detergent,[1] when pure bath soaps fail (see below: Hygiene). Afterward, body lotions could be used to recondition cleansed skin,[1] as would be used to treat dry skin.