No, Keratin doesn't damage your hair. It is a type of protein that is naturally infused into our hair. However, the natural Keratin often gets damaged due to sun exposure and chemicals. In that case, people go for keratin treatments. Although that also brings benefits like manageable, soft, and smooth hair, you should not use Keratin treatment more than three times a year. Also, keratin treatments can be harmful if you overheat your hair  with a blow dryer or flat iron during the process.