What is the ruling on treating hair with keratin, and does it fall under the ruling of talbeed if it coats the hair?

There is no harm in using keratin for treatment if its substance is pure, and it does not cause damage, as long as it does not lead to forbidden adornment or imitation of disbelievers. If the substance is like oil that the hair absorbs, it does not affect ritual purity, and it is permissible to wipe over it. Hair matting is permissible for treatment or benefit, and it is not obligatory to remove it unless it prevents water from reaching the hair during a mandatory ritual bath (ghusl).