Involved in various functions within the body, nicotinic acid aids in red blood cell formation, plays an active role in more than 50 different enzymatic reactions, and is considered necessary to maintain the health of the skin and digestive tract. Consequently, a dietary deficiency of the vitamin is primarily characterized by digestive disturbances and skin lesions. Known as pellagra, this condition may also lead to dementia in severe or prolonged cases. Occurrences of pellagra are most common is countries whose inhabitants eat little or no protein-rich foods, but the illness is also sometimes a side effect experienced by long-term alcoholics. A similar condition that occurs in dogs is known as black tongue disease.