I had been looking into this recently. My beard is graying and it's annoying me excessively.

10 years ago, the research consensus behind hair graying was, "we don't know what causes it, lol." Today, it's a little bit better understood -- though far from completely understood.

There's a handy review article here: https://pmc.ncbi.nlm.nih.gov/articles/PMC10535703/

To summarize, there's no known agent that can reliably repigment gray hair. Sometimes powerful drugs repigment hair as a side-effect.

Hair graying results from the dysfunction or loss of melanogenic melanocytes and the depletion or immobility of McSCs, often due to aging or stress.

Lots of cellular signalling pathways are involved. The Wnt/β-Catenin pathway promotes melanocyte stem cell (McSC) proliferation and differentiation, while the MC1R/cAMP pathway, activated by α-MSH, drives melanin production via the MITF transcription factor. The SCF/c-KIT pathway supports melanocyte survival and function, and the Endothelin/EDNRB pathway stimulates both melanocyte proliferation and melanogenesis. In contrast, the PI3K/AKT pathway inhibits melanogenesis by suppressing MITF activity, and the TGF-β pathway maintains McSC quiescence while inhibiting melanogenesis.

Stress is actually a factor because activation of the sympathetic nervous system can deplete McSCs, and neuropeptides like CGRP, SP, and VIP, can either enhance or suppress melanogenesis in ways which are, as yet, unclear. Dermal white adipose tissue (dWAT) near hair follicles also plays a role by secreting factors such as adiponectin that affect hair growth and pigmentation.

A drug to reverse or prevent hair graying would be very welcome, so I hope that the phenomenon becomes better understood in the near future, and then we get products that work.

> My beard is graying and it's annoying me excessively.

So is mine, and now I've lost most of the hair on my head I shave it so completely bald.

But I've learnt to accept it. I don't like it, and wish it was different. There's nothing I can do and I have plenty of more pressing problems to worry about.

So I keep fit and eat reasonably healthily. So even though I look old, I don't have to act it

Could there be a genetic component to PGH? I started to to get grays at about 14yo so did my sister, and for my mother I only saw her hair color on pictures.

You've obviously done a bit of research. Have you ever seen the vitamin B12 link referenced in other studies? Are you taking supplements or did you get it tested?