Grey Hair

What it is

Hair turns grey as the melanocytes in each follicle make less melanin, so new hair grows in with less pigment [1]. Once the pool of melanocyte stem cells in the follicle is depleted, greying is usually permanent [2]. Greying is common: about a quarter of 6,390 men under 30 already had some grey hair in one survey [3], and 55.9% of 1,193 respondents in a Saudi survey reported grey hair before age 30 [4].

How it might work

Proposed drivers include oxidative stress in the follicle, melanocyte stem-cell exhaustion and weaker pigmentation signalling, with genes setting much of the timing [2]. Some grey hairs regain colour, and drugs and hormones can trigger repigmentation, which shows the process is not always one-way [2]. Psychological stress has been linked to greying, and single-hair mapping found greying and reversal events that paralleled periods of stress and relief [5].

What the research says

For reversing or preventing grey hair, the evidence is thin. A 2025 review found no permanent treatment and limited options [6]. The best-controlled test was a 24-week randomised trial of 44 women: a Pueraria lobata extract lotion reduced new grey hairs (6.3 vs 11.4 per cm2) but produced no visible change [7]. A systematic review of 27 reports of medication-induced repigmentation called the evidence low-quality [8]; case reports describe results with alpha-MSH peptide lotions [9]; and an uncontrolled 10-patient series reported improvement with exosome injections [10].

For deficiency correction, case-control studies found lower vitamin B12, folate and biotin in patients with premature canities [11], and vitamin B12 deficiency and hypothyroidism were strongly associated with early greying in a 71-patient series [12], while a 300-versus-300 study found low ferritin associated instead [13]. A 2020 systematic review and meta-analysis reported reversal after treating associated conditions 'in many cases' and gave a low-grade (2A) recommendation to calcium pantothenate and PABA [14].

For risk factors, family history is the strongest and most consistent: 90.1% of one Indian series had a family history [12], and among 6,390 young men family history carried an odds ratio of 12.82, ahead of obesity (2.61) and smoking more than 5 pack-years (1.61) [3]. A review of 32 studies found premature greying more common in smokers [15], and a 2,644-person survey linked higher stress to earlier onset [16]; one 600-person case-control study found no smoking link, showing the surveys disagree [13].

Doses used in studies

Pueraria lobata extract (APHG-1001) applied twice daily for 24 weeks [7]; palmitoyl tetrapeptide-20 lotion at 10 ppm applied daily for 3 months [17]; calcium pantothenate 200 mg a day plus vitamin E, alongside plucking of grey hairs, in a 1986 study of 39 girls [18]. These are the doses used in research, not recommendations.

Safety and interactions

Hair dyes: contact allergy to p-phenylenediamine (the main allergen in permanent dyes) occurs in an estimated 0.1-2.3% of the general population [19]. 'Black henna' mixes that add p-phenylenediamine sensitised about 2.5% of users in one review, and topical henna can cause life-threatening haemolysis in children with G6PD deficiency [20]; allergy to pure henna is uncommon but documented [21]. Supplements: He Shou Wu (Polygonum multiflorum), used in some anti-grey formulas, has been linked to idiosyncratic liver injury in many countries [22], and biotin supplements can interfere with laboratory tests, causing false results [23]. Medicines that have darkened grey hair as a side effect, such as psoralens and immunosuppressants, are prescription drugs for other conditions and are not approved for greying [8]. No studies were found of anti-grey products in pregnancy or breastfeeding; supplement use while pregnant or breastfeeding is a question for a doctor. No product has an established effective dose or long-term safety record for greying [6].

Caveats and open questions

No controlled trial has yet shown a visible colour change from any marketed remedy [7], and product studies tend to measure cells or proteins rather than appearance [17]. Surveys conflict on smoking and on ferritin [3][13]. The stress evidence comes from small studies [5]. Reviews call for rigorous clinical trials of greying treatments, which may settle these questions [6].