Collagen for hair growth: what's plausible, what's proven, what we've seen

Collagen is widely sold for hair growth, and plenty of people who take it say their hair got thicker and grew faster. We're one of them. But if you go looking for the trial that proves it, you won't find one. This page explains what collagen can plausibly do for hair, what the research has and hasn't tested, and how to try it properly if you want to.

What hair is made of, and where collagen fits

Hair isn't made of collagen. The strand itself is keratin, a different protein. Collagen is in the skin around the follicle: the dermis, where each follicle is anchored, is about three-quarters collagen by dry weight, and the dermal papilla at the base of the follicle, which drives the growth cycle, sits in a collagen-rich matrix.

So the plausible routes are indirect. Collagen peptides supply amino acids (proline, glycine) that keratin also uses, and the skin trials show that collagen peptides improve the dermis, which is the follicle's environment. That's a reasonable mechanism. It isn't a result.

What the research actually shows

Skin: good evidence. 2.5g a day of specific collagen peptides over 8 weeks improved elasticity and wrinkle depth in placebo-controlled trials. Summarised in Does collagen actually work for skin?

Nails: 1 decent study. 2.5g a day for 24 weeks gave 12% faster nail growth and fewer broken nails in 25 women. Open-label, no placebo group, so treat it as suggestive.

Hair: no placebo-controlled trial of collagen peptides on hair growth, thickness or shedding that we can point you to. Some small studies have tested hair supplements that contain collagen alongside biotin, zinc and other ingredients, which tells you nothing about the collagen itself.

That's an honest gap, not a hidden negative. Nobody has run the trial. Until someone does, "collagen for hair growth" is a plausible idea with personal accounts behind it, not a proven one.

Which collagen type for hair?

You'll see guides ranking Types I, III and V for hair. Ignore them. Once collagen is hydrolysed into peptides, the "type" label mostly describes the source tissue, not what the peptides do in you. Bovine collagen is Type I and III, the same types found in the skin around your follicles, and the skin trials used bovine Type I peptides. There's no evidence that any other type does more for hair.

What matters more than type: peptide size (about 2,000 Daltons in the skin research), a consistent daily dose, and sticking with it long enough to see a hair cycle through.

What actually drives hair loss

If your concern is thinning rather than growth speed, the causes with evidence are: genetics and DHT (pattern hair loss in men and women), iron deficiency, thyroid problems, post-pregnancy and post-illness shedding, crash dieting and low protein intake, and some medications. Collagen addresses none of those directly except low protein. A GP can test iron and thyroid with a simple blood test, and that's the first step before any supplement.

How to try it properly

• Dose: 2.5g to 5g a day, the skin-trial range. More won't speed hair up.
• Duration: at least 3 months. Hair grows about 1cm a month and new growth takes weeks to show at the surface, so judging at 4 weeks is too early.
• Measure something: a photo of your parting in the same light each month, or how far roots have grown out between colours. Memory is unreliable.
• Cover the basics: enough protein overall (hair is protein), iron if you're low, and a source of vitamin C with the collagen.

Frequently asked questions

Collagen or biotin for hair?
Biotin only helps if you're deficient, which is rare. Collagen has the better skin evidence and the same hair evidence gap. Side by side in Biotin vs collagen.

Does marine collagen work better for hair?
No evidence it does. We don't sell marine collagen; our range is bovine, which is what the skin trials used.

Can collagen cause hair loss?
No. It's a food protein. If shedding started around the time you began a supplement, look at what else changed (diet, stress, illness, medication) and see a GP.

Vegan options?
No plant contains collagen. The plant-based route is silica and vitamin C to support your own production: Does vegan collagen work?

The studies

• Proksch E, Zdzieblik D, Oesser S (2025). Bovine collagen peptides, dermal matrix synthesis and clinical skin parameters. Cosmetics 12:79. Read it free →
• Hexsel D et al. (2017). Oral supplementation with specific bioactive collagen peptides improves nail growth and reduces symptoms of brittle nails. Journal of Cosmetic Dermatology 16:520–526. View →

This article is general information, not medical advice. Sudden or patchy hair loss should be checked by a doctor.

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