Skin

Skin
	Layers of human skin (Wikimedia Commons, PD)
Field	Face ; ;

Skin is the body's outer protective organ, with roles in sensation, temperature regulation and preventing water loss. Its appearance includes colour, texture and visible conditions such as acne. In looksmaxxing, these appearance-related questions are discussed under skin clarity, while sunscreen concerns protection from ultraviolet exposure.^[1] Facials and specific treatments have separate articles.

Structure and functions

Skin is the body's largest organ. It forms a protective covering, helps prevent dehydration, participates in defence against germs, regulates temperature and provides sensation. Its roles therefore extend beyond visible appearance. The National Institute of Arthritis and Musculoskeletal and Skin Diseases also identifies the production of melanin and vitamin D among its functions.^[1]

Epidermis, dermis and underlying tissue

The epidermis is the outer layer. New cells form below the surface while older cells are shed. The dermis beneath it contains blood vessels, nerve endings and glands. NIAMS's introductory account also describes the hypodermis, the deeper tissue associated with energy storage and connection to underlying structures. These layers and their different components explain why a change visible at the surface may have several possible causes.^[1]

Melanin contributes to skin colour and protection from the sun's rays. Sweat glands help with temperature regulation, while nerves convey information about touch, pressure and temperature. Hair follicles belong to this system as well; they are not simply decorative structures placed on an otherwise inactive covering.^[1]

Injury and repair

Following a cut or scrape, platelets participate in the formation of a clot. A scab can cover the damaged area while new cells replace injured tissue. Deeper damage may leave a scar. This repair process is distinct from an immediate cosmetic change in colour or texture.^[1]

A bruise, by contrast, can occur beneath an unbroken surface when small blood vessels are damaged. NIAMS explains the characteristic changes in colour as the material from the damaged vessels is broken down. The surface appearance alone does not make a bruise equivalent to pigmentation, acne or a scar.^[1]

Conditions and appearance

NIAMS discusses conditions including acne and eczema as health problems with differing causes and manifestations. Eczema can involve dry, itchy patches and triggers that vary between individuals. Acne is not explained simply by declaring the skin dirty. Treating every visible mark as the same problem obscures these distinctions.^[1]

In an appearance encyclopedia, Skin clarity, Acne, Sunscreen and related articles address narrower questions. Anatomy supplies a basis for understanding those topics, but it does not establish that a particular cosmetic product or treatment is appropriate for an individual. Modern treatment claims require current evidence in addition to a historical anatomical illustration.