Funnily enough, I got this question as part of my holiday homework. I'm not sure if this is correct but this is what I wrote:
"Hair is composed of the protein Keratin which is an alpha helix. It is able to stretch and its hydrogen bonds can be broken when heat is applied, but it eventually returns to its original shape as hydrogen bonds form over time."
Would water (H2O) help in these hydrogen bonds in forming?
In biology, Hydrogen bond is considered to be a quite weak bond, it can easily break and reform (that's why water is cohesive). Hydrogen bond is made from when an H+ attracts an N,O, or F. Hence, in water, when H+ attracts to OH-, it will create a water molecule. In Keratin, if you look at the alpha helix structure, it's quite flexible, easily stretch since H-bond is weak but easily rejoin since the H+ and O- will try to attract to each other, making the bond cohesive.
Another reason is, keratin contains cysteine amino acids, these amino acid contains Sulfur element. if 2 cysteines meet, they can build a disulphide link between them. Imo, if you add water, then these H+ and O- along the chain will not attract to each other anymore ( or less attract) since there are more H+ and OH- from the added water molecules, therefore, it will break the bond.
These are just my knowledge and might contain some errors
, still, hope this makes sense.