Biotin is a B-vitamin and coenzyme that plays several roles in the human body and affects the skin and nerves. It supports digestive health and plays a role in cellular metabolism. According to WebMD, a normal diet along with the body's recycling of previously used biotin satisfies the body's requirements for the nutrient, which means actual biotin deficiencies are rare and taking biotin supplements is usually not necessary.
Biotin supplements are likely effective in treating biotin deficiencies. Such deficiencies cause thinning of the hair and loss of hair color. A scaly red rash surrounding the mouth, nose and eyes is another symptom of a biotin deficiency. A lack of biotin is also associated with symptoms including depression, hallucinations and listlessness. Some studies show people who smoke cigarettes are more likely to be deficient in biotin, according to MedlinePlus.
Due to the lack of biotin deficiencies, Mayo Clinic indicates there are no recommended daily amounts for the supplement, but the normal daily intake for adults ranges from 30 to 100 micrograms per day. With normal intake, biotin is unlikely to cause any side effects, although it has the potential to cause interactions with other medications, tobacco or alcohol. Before beginning supplementation with over-the-counter products containing biotin, speak with a doctor about any possible risks.