Donating organs for cases of necessity is considered permissible. One of the conditions is that the donor must not endanger their own health. In the case of hair donation, such a risk does not arise; therefore, it is permissible. Moreover, if this donation helps to alleviate, even partially, the effects of serious and traumatic illnesses such as cancer, it may even be regarded as commendable.
The fact that the donated hair may be seen by non-mahram individuals or used without covering does not impose any responsibility on the donor. Once the hair is separated from the body, it no longer entails any obligation for its original owner.