Hi.. I did Global Keratin Hair treatment twice and it works well on my hair :) but my question; does keratin cause cancer? I will greatly appreciate your sincere feed back. Thank You. – anon14564 Hair and nails on humans especially tend to become dry and brittle, because the dead keratin is being pushed to great lengths. By eating foods like and keeping hair and nails moist, they can be grown out while still remaining healthy. In general, the thicker the layer of keratin, the healthier the hair or nail is, because the dead cells outside protect the living cells at the core. Keeping the external layer of keratin moisturized will also keep it healthy and prevent cracking and splitting, whether the keratin is forming the hooves of a horse of the skin of a human..