Encyclopedia
Every molecule that touches your hair
From proven medicines to kitchen-cupboard oils, with the studies behind each one.
11 entries
A
-
protein or peptide
Afamelanotide and melanotan
Skin-tanning peptides discussed online as hair-darkeners, but no study shows any effect on gray hair, and unlicensed melanotan injections have been linked to melanoma in case reports.
B
-
botanical
Bhringraj
Bhringraj is the Ayurvedic "king of hair" herb; extracts speed regrowth in rats and mice, but no human hair trial was found.
C
-
supplement
Catalase and pseudocatalase
The idea that hair grays because follicles accumulate hydrogen peroxide has a real basis in vitiligo skin, but catalase supplements for gray hair have no human trial evidence.
H
-
botanical
Hibiscus
Hibiscus leaf and flower extracts grew hair in rats and cultured rat follicles, but no human hair trial exists.
-
chemical treatment
Hydrogen peroxide
The oxidiser in every bleach and permanent dye; it lifts colour by destroying melanin but also oxidises the hair's own proteins, so damage rises with strength and repeat use.
I
-
drug with hair side effects
Imatinib
A leukaemia drug that blocks the receptor pigment cells depend on can lighten or whiten hair reversibly, and oddly has also been listed among drugs that darkened gray hair.
-
drug with hair side effects
Immune checkpoint inhibitors (nivolumab, pembrolizumab)
Anti-PD-1 cancer immunotherapy darkened white hair in 13 of 14 lung cancer patients in one series, and in a single case left a persistent curly-hair look.
L
-
supplement
Luteolin
A plant flavonoid sold as a supplement slowed hair graying in a mouse model while two similar antioxidants did not, and there is no human data at all.
P
-
colorant
p-Phenylenediamine (PPD)
The main dark permanent dye ingredient and one of the commonest hair-dye allergens; it colours well but can cause severe contact dermatitis in sensitised people.
-
supplement
Para-aminobenzoic acid (PABA)
A 1950 physician report described gray hair darkening on high-dose PABA, and the idea has survived 75 years on weak evidence.
V
-
supplement
Vitamin B12
A real but uncommon cause of hair loss when deficient, with no evidence that extra B12 helps hair if your levels are normal.