A skin ulcer describes a sore on the skin that causes a complete loss of the outer layer of skin, some inner layers of skin and in some cases the subcutaneous fat. Skin ulcers may appear red or swollen and may bleed or ooze fluids. Although a lack of blood circulation most commonly causes skin ulcers, many types of diseases can cause the formation of skin ulcers.
Anthrax
Anthrax, a disease caused by the bacterium Bacillus anthracis, usually spreads to humans through direct or indirect contact with infected animals. The most common form of anthrax, known as cutaneous anthrax, occurs when the bacteria enter the skin through a cut or sore. Although anthrax infection is deadly, cutaneous anthrax usually produces mild symptoms. Even when left untreated, 80 percent of cutaneous anthrax cases aren't fatal, according to the Centers for Disease Control and Prevention. Cutaneous anthrax causes small skin blisters that develop into skin ulcers with a black area in the middle. Although the ulcers appear serious, they are not painful.
Basal Cell Carcinoma
Basal cell carcinoma, the most common form of skin cancer, affects approximately 2 million people every year, according to The Skin Cancer Foundation. Basal cell carcinoma usually affects the areas of skin exposed to the sun, such as the face, ears, neck, scalp, shoulders and back. The skin lesions caused by basal cell carcinoma vary and can resemble non-cancerous skin conditions. A reddish, irritated-appearing patch on the skin can indicate the presence of basal cell carcinoma. Other patients will notice a small shiny bump or a pink growth. The formation of a small ulcer that bleeds or continually oozes and fails to heal is a common early sign of basal cell carcinoma.
Scleroderma
Doctors classify scleroderma, also known as system sclerosis, as an autoimmune rheumatic disease. Although the exact cause remains unknown, scleroderma involves an overproduction of collagen---a fibrous protein that makes up connective tissues. Scleroderma initially affects the skin, causing hardening of the skin, but can also affect other organs in the body. Scleroderma can cause Raynaud's phenomenon, according to MayoClinic.com, in which the blood vessels in the hands and feet constrict, resulting in numbness and pain. The changes in the skin caused by scleroderma, along with the restricted blood flow, can lead to the formation of skin ulcers on the fingers and toes, as described by the International Scleroderma Network.
Inflammatory Bowel Disease
Inflammatory bowel disease---IBS, a term used to describe a group of diseases that cause inflammation of the digestive tract--usually causes chronic and sometimes bloody diarrhea. IBS can also cause other symptoms unrelated to the intestines, including pyoderma gangrenosum. Pyoderma gangrenosum causes the formation of small red bumps that appear like blood blisters. The skin around the blisters continues to break down, resulting in skin ulcers that can deepen and widen rapidly, according to doctors at the Mayo Clinic.
