Why Does Hair Turn Grey: Causes and What Actually Helps (2026)

Quick answer (as of October 2026): Hair turns grey when the pigment-making cells in each follicle stop being replenished. A landmark 2023 study showed the stem cells responsible get physically stuck in the follicle and can no longer mature into colour-producing cells [1]. Genetics sets the schedule, which is why grey hair runs in families [2]. Stress, smoking and deficiencies in B12, iron and thyroid hormones can accelerate it [3,4]. There is no proven pill or shampoo that reverses greying, but when a deficiency or thyroid problem is the driver, correcting it can restore some pigment.

Grey hair is one of the most searched hair questions in the UK, and one of the most myth-loaded. This guide covers what actually causes it, what is worth checking, and what genuinely helps.

Why does hair turn grey?

Each hair gets its colour from melanin, delivered by pigment cells called melanocytes at the base of the follicle. Those melanocytes are renewed from a pool of stem cells.

In 2023, researchers showed exactly how that renewal fails. Melanocyte stem cells normally shuttle between two compartments in the follicle, switching states as they go. With age, more and more of them get stuck in one compartment, unable to move back and mature. No mature melanocytes, no pigment, and the hair grows through grey or white [1].

Age and genetics do most of the scheduling. The first gene linked to grey hair, IRF4, was identified in 2016, and family history remains the strongest predictor of when you will go grey [2].

What counts as premature greying?

Greying is usually called premature when it starts before the age of 20 in people of white European ancestry, before 25 in people of Asian ancestry and before 30 in people of African ancestry [4]. Going grey at 30 is common and normal. Going grey at 20 is worth a conversation with a doctor, not because it is dangerous, but because it is occasionally a flag for something fixable.

Does stress cause grey hair?

Partly, and the science here is newer than most people think. In 2021, researchers mapped pigment loss along individual human hairs and found periods of greying that lined up with reported stressful periods, and, in a small number of hairs, re-pigmentation when the stress passed [3]. The effect is real but modest: stress can nudge the timeline, not override your genes. The idea that fright turns hair white overnight is a myth; hair that has already grown cannot change colour.

Can a deficiency cause grey hair?

Yes, and this is the practical part. Premature greying has been linked to low vitamin B12, low ferritin (iron stores) and thyroid disorders in clinical studies [4,5]. Smoking is also associated with earlier greying [4]. These are checkable with a simple blood test, and when a deficiency is the driver, correcting it can restore some pigment, particularly in younger people. It is the one grey-hair intervention with a real mechanism behind it.

Does plucking a grey hair make more grow?

No. Each follicle produces one hair. Plucking removes that hair; it does not signal neighbouring follicles to turn grey. The myth survives because greying is progressive anyway: by the time you notice one grey, others are already on their way. Plucking is still a bad idea, because repeated plucking can damage the follicle and thin the hair permanently.

What actually helps?

Honesty first: no shampoo, supplement or serum has been shown to reverse established genetic greying. Products claiming otherwise are ahead of their evidence.

What genuinely helps, in order of usefulness:

1. Check the fixable causes. If greying came early or fast, test B12, ferritin and thyroid function [4,5].
2. Stop smoking. Associated with earlier greying, and quitting helps everything else too [4].
3. Manage the hair you have. Grey hair is often drier and wirier because oil production falls with age. Gentle care, less heat and conditioning go further than any miracle cure.
4. Look after density, not just colour. Most people bothered by greying are also noticing texture and thickness changes. That part is very treatable.

Can PRP help with grey hair?

Directly, no, and we will not pretend otherwise. PRP works on follicle health and hair thickness, not on pigment cells. What PRP does well is improve the calibre, density and condition of the hair itself, which is usually the bigger concern behind the question. We have written separately about the interesting early research on PRP and hair pigment, and where the limits sit.

In our internal case study completed in March 2026, 87 percent of patients showed visible improvement in hair quality and coverage at their week-16 photo review. Hair PRP at The London PRP Clinic is £450 per session or £1,215 for a course of three, starting with an assessment that maps your pattern, checks for treatable drivers and agrees what success would look like.

Message the team on WhatsApp with your questions, or call 020 3951 3429.

Frequently asked questions

Why am I going grey at 25?

Almost always genetics [2]. But 25 sits at the edge of the premature range, so a one-off blood test for B12, ferritin and thyroid is sensible reassurance [4,5]. If those are normal, your timeline was simply written early.

Does stress really cause grey hair?

It can accelerate it. A 2021 study documented greying and occasional re-pigmentation in step with stressful periods in individual hairs [3]. Genetics still does most of the work.

Does plucking one grey hair cause more to grow?

No. One follicle, one hair. More greys appear because greying is progressive, not because you plucked.

Can grey hair turn back to its natural colour?

Usually no. The exception is greying driven by a correctable cause such as B12 deficiency, thyroid disease or a period of intense stress, where some re-pigmentation has been documented [3,4].

Does B12 deficiency cause grey hair?

Low B12 is associated with premature greying in clinical studies, and correcting a true deficiency can restore some pigment [4,5]. Supplementing when your levels are already normal has no proven effect on colour.

Is grey hair weaker or thinner?

The hair itself is often coarser but more brittle, and oil production falls with age, so grey hair feels drier. Density loss is a separate process that often arrives at the same time, which is why the two get confused.

Does smoking cause grey hair?

Smoking is associated with significantly earlier greying in observational studies [4]. One more reason to stop.

Can PRP restore hair colour?

No. PRP improves the health, thickness and calibre of hair from living follicles; it does not act on pigment cells. Early research on PRP and pigmentation is interesting but preliminary, and we cover it honestly in a separate guide.

Sources

1. Sun Q et al. Dedifferentiation maintains melanocyte stem cells in a dynamic niche. Nature, 2023. https://www.nature.com/articles/s41586-023-05960-6
2. Adhikari K et al. A genome-wide association scan identifies loci influencing hair colour and morphology. Nature Communications, 2016. https://www.nature.com/articles/ncomms10815
3. Rosenberg AM et al. Quantitative mapping of human hair greying and reversal in relation to life stress. eLife, 2021. https://elifesciences.org/articles/67437
4. Kumar AB, Shamim H, Nagaraju U. Premature graying of hair: review with updates. International Journal of Trichology, 2018. https://doi.org/10.4103/ijt.ijt_47_18
5. Daulatabad D et al. Association of serum vitamin B12, ferritin and thyroid profile in premature hair greying. https://pmc.ncbi.nlm.nih.gov/articles/PMC5448266/

The Wellness Clinical Team. Sources checked 22 October 2026. General information, not an individual diagnosis or treatment plan.