Research has demonstrated that biotin hair growth supplements do not seem to improve hair growth except in extreme cases including:
- Severe deficiency from malnutrition
- Removal of portions of the intestines
- Malabsorption caused by gastrointestinal disease
- Neurological diseases
- Enzyme deficiency
- Treatment with antiepileptic medication or broad-spectrum antibiotics
Overconsumption of raw egg whites can also cause biotin deficiency.