research Reversible Hypopigmentation of Hair Secondary to Vitamin B12 Deficiency 1 citations, January 2013 in “Nasza Dermatologia Online” Vitamin B12 deficiency can cause reversible hair color loss in children.
research Knuckle Hyperpigmentation as a Preliminary Marker of Vitamin B12 Deficiency: A Case Series July 2021 in “PARIPEX INDIAN JOURNAL OF RESEARCH” Knuckle darkening can be an early sign of vitamin B12 deficiency.