Biotin is a coenzyme and a B vitamin. It is also known as vitamin H. Biotin is used for preventing and treating biotin deficiency associated with pregnancy, long-term tube feeding, malnutrition. It is also used orally for hair loss, brittle nails, skin rash in infants (seborrheic dermatitis), diabetes, and mild depression. Symptoms of deficiency include thinning of the hair (often with loss of hair color), and red scaly rash around the eyes, nose, and mouth. Other symptoms include depression, listlessness, hallucinations, and tingling in the arms and legs. There is some evidence that cigarette smoking may cause mild biotin deficiency. There isn’t a good laboratory test for detecting biotin deficiency, so this condition is usually identified by its symptoms, which include thinning of the hair (frequently with loss of hair color) and red scaly rash around the eyes, nose, and mouth. Nervous system symptoms include depression, exhaustion, hallucinations, and tingling of the arms and legs. On its own, biotin might decrease insulin resistance and nerve symptoms related to type 2 diabetes. Pregnant women sometimes have low levels of biotin, so some take biotin supplements.