Biotin is a type of B vitamin, but it's sometimes called vitamin H, for haut, the German word for skin. In humans, biotin deficiency can cause lethargy, depression and a scaly rash around the eyes, nose and mouth. Balanced diets normally provide all the biotin people need -- the vitamin is particularly plentiful in liver, egg yolks, yeast, salmon, carrots and peanuts.
Uses: Supplements are prescribed to treat biotin deficiency, which is caused by rare genetic disorders. Some people take it in hopes of combating acne, eczema, brittle nails, cowlicks, high cholesterol and low blood sugar. Biotin is sometimes used in attempts to stop hair from graying or thinning.
Dose: Biotin is available by itself and in many multi-ingredient supplements. Supplemental doses range from a few hundred micrograms to a few milligrams per day. Healthy adults usually get 30 to 100 micrograms of biotin a day from their diets.
Precautions: Biotin supplements are generally considered safe.
Research: There's no good evidence that biotin supplements can reduce acne, tame cowlicks or reverse hair loss or graying. Some studies suggest it may help combat brittle nails. Animal studies suggest biotin may also help improve glucose metabolism in people with Type 2 diabetes, but much more research is needed to confirm its effects.