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Editor-In-Chief: C. Michael Gibson, M.S., M.D. 
Biotin deficiency can have a very serious, even fatal, outcome if it is allowed to progress without treatment. Signs and symptoms of biotin deficiency can develop in persons of any age, race, or gender. Biotin deficiency rarely occurs in healthy individuals, since the daily requirements of biotin are low, many foods contain adequate amounts, intestinal bacteria synthesize small amounts, and the body effectively scavenges and recycles biotin from bodily waste. However, deficiency can be caused by excessive consumption of raw egg-whites over a long period (months to years). Egg-whites contain high levels of avidin, a protein that binds biotin strongly. Once a biotin-avidin complex forms, the bond is essentially irreversible. The biotin-avidin complex is not broken down nor liberated during digestion, and the biotin-avidin complex is lost in the feces. Once cooked, the egg-white avidin becomes denatured and entirely non-toxic.
Initial symptoms of biotin deficiency include:
- Dry skin
- Brittle nails
- Seborrheic dermatitis
- Fungal infections
- Rashes including erythematous periorofacial macular rash
- Fine and brittle hair
- Hair loss or total alopecia
If left untreated, neurological symptoms can develop, including:
- Mild depression, which may progress to profound lassitude and, eventually, to somnolence
- Changes in mental status
- Generalized muscular pains (myalgias)
- Hyperesthesias and paresthesias
The treatment for biotin deficiency is simply to start taking some biotin supplements.
Biotin deficiency should not be confused with biotinidase deficiency, which is not due to inadequate biotin, but rather to a deficiency in the enzymes which process it.