Is it permissible to perform ablution (wudu') without washing the hair before it, knowing that the anti-hair loss substance used is applied to the scalp, is non-alcoholic, and evaporates after a period?

If the mentioned substance does not prevent water from reaching the hair being wiped, then it does not affect the validity of wiping over the head. However, if it is placed on the hair and has a bulk that prevents water from reaching it, then it must be removed during ablution because it acts as a barrier. It is permissible for a man to wipe over his turban.