How does riboflavin deficiency affect hair growth?

Riboflavin or vitamin B2 is a water-soluble vitamin that's part of the B complex vitamins. Riboflavin is needed for collagen production, which leads to healthy hair so a deficiency would interfere with that. Additionally, riboflavin plays a crucial role in activating niacin and vitamin B6, both needed for healthy hair. So a deficiency in riboflavin would lead to less of these nutrients, thus interfering with hair growth.