Skin ulcer is a sore on the skin or a mucous membrane, accompanied by the disintegration of tissue. An ulcer that appears on the skin is often visible as an inflamed tissue with an area of reddened skin. A skin ulcer is often visible in the event of exposure to heat or cold, irritation, or a problem with blood circulation. Ulcers can result in complete loss of the epidermis and often portions of the dermis and even subcutaneous fat. They can also be caused due to a lack of mobility, which causes prolonged pressure on the tissues. This stress in the blood circulation is transformed to a skin ulcer, commonly known as bedsores or decubitus ulcers. Ulcers often become infected, and pus forms.