Harrys Keratin Treatment Cashmere Intense Repair Mask: Why Many Consider It The Best Keratin Hair Mask. We no longer present it, so well known to those who are committed to providing the best for their hair. Indispensable, keratin is naturally present in the hair and it is also a very precious ingredient which is included in the composition of many hair care products. The Keratine Treatment Harrys mask is a high performance product, mainly used in professional hairdressing salons. Its exclusive use gives it a rarity which makes this treatment a product intended for professional use. It is one of the most concentrated keratin masks on the market today, which is why it is very popular with hairdressing professionals. At the heart of its formulation, shea butter, cashmere keratin, a magnesium complex and jojoba oil. The presence of keratin plays a big role in the active principle of this hair treatment and it is this which strengthens the internal structure of the hair. Rehydrated, the hair is nourished deeply and durably but also protected from external aggressions. The hair is transformed into a stunning texture where suppleness, softness and velvety shine meet.