Keratin vs Biotin: which one actually repairs damaged hair?
Keratin rebuilds the hair shaft from the outside; biotin supports growth from within. Here's how each one works, when to use them, and which one fixes damaged, frizzy, or color-treated hair fastest.
The short answer
Biotin is a B-vitamin taken internally — it supports the follicle so new hair grows in healthier. Keratin is the structural protein your hair is already made of — applied topically, it rebuilds the surface of strands you have right now. If your hair is damaged, frizzy, or color-treated, keratin is the faster fix.
Keratin
Topical · works on existing hair
- Fills in damaged gaps along the hair shaft
- Smooths the cuticle for instant shine
- Visible results after the first wash
- Best for heat damage, bleach, color, frizz
Biotin
Oral · works on future hair
- Supports keratin production in the follicle
- May help with thinning linked to deficiency
- Results take 3–6 months of consistent use
- Won't repair strands you already have
How keratin actually repairs hair
Each strand is roughly 90% keratin. Heat tools, bleach, and color treatments break those protein bonds and lift the cuticle — that's what "damaged" hair physically is. Hydrolyzed keratin in a mask is small enough to slot into those broken sections and bond, rebuilding the strand from the outside in. You feel it as softness; you see it as shine and frizz disappearing.
When biotin helps (and when it doesn't)
Biotin matters if you're genuinely deficient — which is rare. For most people with damaged hair, more biotin won't undo broken bonds in the strands already on your head. It supports what grows in the future. If your concern is "my hair feels rough, looks dull, breaks at the ends," biotin is the slow path. A keratin treatment is the direct one.
Can you use both?
Yes. They work on different layers — keratin treats the strand, biotin supports growth. If your hair is currently damaged, lead with a topical keratin treatment for immediate repair, then consider biotin as a long-term follicle-health habit if your doctor agrees.
The verdict
For damaged, frizzy, color-treated, or heat-styled hair you want fixed now, keratin wins. Biotin is a long game for growth — not repair.