Keratin the same thing your fingernails are made of!
Sebaceous glands secrets sebum into the hair follicle which keeps the hair and epidermal surface pliable and waterproof
Sebum, which is secreted by the sebaceous glands connected to the hair follicles. Sebum keeps the hair and skin supple and waterproof, and is also a natural antiseptic that can reduce the growth of microorganisms.
Keratin is the protein that keeps hair flexible, providing strength and resilience. In the skin, lipids within the epidermis create a barrier that waterproofs the dermis, preventing water loss and protecting against external elements. Together, keratin and lipids play crucial roles in maintaining the integrity and functionality of hair and skin.
I think they are waterproof. I have a blue feather and I wash it when i wash my hair
Air trapped in their fur keeps them warm
Wax
hair is flexible nails aren't flexible, you can dye hair you can only paint nails and so on
the fact that it is probably waterproof !! ;)
Cysteine
It keeps it flexible and living by all the voting.
Your haur keeps your hair in place as it is imbedded into your brain!
Some yes, some no. Depending on the brand you get, there can be some that are and some that aren't waterproof.