L'Oréal Professionnel Serie Expert Keratin Alpha Sleek Serum 50ml

Why you'll love it

• A high-performance finishing serum for ultra-smooth, glass-like shine
• Long-lasting frizz control, up to 2 weeks of frizz control with regular use¹
• Helps refine the hair surface, tame flyaways and reduce the look of split ends
• Fights up to 80% humidity³ with heat protection up to 230°C4
• Lightweight, so it smooths without weighing hair down, for all hair types

Glass-like shine and serious frizz control in one drop. L'Oréal Professionnel Keratin Alpha Sleek Serum is a high-performance finishing serum designed to deliver ultra-smooth, mirror-like shine with long-lasting frizz control. Perfect for unruly, frizz-prone or chemically treated hair, the lightweight formula helps transform dull, rough-looking strands into a sleek, polished finish without weighing the hair down. Infused with keratin-inspired smoothing technology, it helps refine the hair's surface, improve manageability and enhance softness with every use, for impeccably smooth, radiant hair that feels as luxurious as it looks.

What it does for your hair

Frizz, flyaways and a rough-looking surface are what make hair look dull and unpolished. This serum helps on all fronts: keratin-inspired smoothing technology helps refine and smooth the hair's surface for a glass-like, mirror shine, while helping tame flyaways, reduce the appearance of split ends and improve manageability. It also helps protect your style against humidity (up to 80%³) and adds heat protection up to 230°C4, so your sleek finish holds up through the day, and it can cut your styling time down too. The result is visibly healthier-looking, luminous, sleek hair, without any heaviness. It works hardest as part of the full Keratin routine.

How to use it

Warm a small amount between the palms and work through damp or dry hair, focusing on the mid-lengths and ends where frizz and roughness concentrate. Use before blow-drying for smoothness and heat protection, or on dry hair as a finishing touch for shine and flyaway control. A little goes a long way, so start small and build up.

Who it's for

This one's for anyone with unruly, frizz-prone or chemically treated hair who wants sleek, glossy, controlled hair with humidity resistance and heat protection built in. We've been perfecting colour, blow-dries and styling for clients in Codsall for years, and a good smoothing serum is one of the quickest ways to take hair from rough and dull to sleek and mirror-shiny.

Build your routine

Smoothness works best as a full routine, so pair the serum with the matching Keratin shampoo and mask. Find them and more in our shampoo collection, explore more smoothing and anti-frizz options across our hair products, or browse our shop by brand pages for your favourites.

Free UK delivery on all orders.

¹Up to 2 weeks of frizz control: consumer test on 68 participants, 1 application per week for 4 weeks, based on a 15-day break observation. ²Instant shine lasting up to 5 days: instrumental test after 1 application of shampoo, mask and serum. ³Up to 80% humidity: instrumental tests, full routine after 4 uses. 4Heat protection up to 230°C (450°F): instrumental tests. 5Styling in half the time: instrumental tests with the full routine. Contains fragrance; patch test before use if you have sensitive skin.