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.