The human skin is the largest organ of the human body. It acts as a barrier and provides protection against the external environment: viruses, bacteria, sun, pollution, and wounds. Dermatology is the medical specialty that focuses on the physiology and diseases of the skin, mucous membranes and skin appendages (hair, nails). The most common skin diseases are acne, psoriasis, sun allergies, and skin cancers. It is important to monitor your skin and consult a doctor when a change occurs (change in appearance of a mole, redness, wound).