L'Oréal Professionnel Keratin Alpha Sleek Hair Serum locks in that smooth, just styled finish and keeps frizz under control for longer. This serum works by sealing the hair’s keratin structure, helping maintain sleekness, reduce volume and protect against humidity that causes frizz to come back. The 5% Keratin Sealer forms a protective layer over the fibre, keeping hair smooth and controlled for up to 10 washes while boosting shine. It also acts as a heat protectant up to 230°C, making it ideal for blow drying and straightening, while helping cut styling time in half by making hair easier to manage. Anti humidity protection up to 80% means your style holds even in damp conditions, so hair stays sleek, polished and frizz free for longer. Used as part of the full routine, it helps maintain up to 2 weeks of smooth, controlled hair with a glossy, mirror like finish.