L'Oréal ProfessionnelKeratin Alpha Sleek Hair Serum, Anti Fririzz, Heat Protection, Smoothing & Glass
L'Oréal Professionnel Keratin Alpha Sleek Hair Serum, Anti Frizz, Heat Protection, Smoothing & Glass Shine 50ml
Reprograms hair for up to 2 weeks of frizz control1
•\tUp to 5x smoother hair and 2x less frizz2
•\tControls unwanted volume for daily styling in half the time3
Keratin Alpha Sleek Mirror Sleek Serum, formulated with Keratin Sealer 5%. The Mirror Sleek serum seals the hair's keratin structure to:
•\tDelivers instant shine that lasts up to 5 days.4
•\tThe serum helps to fight against up to 80% humidity5
•\tHeat protection up to 230°C (450°F)6
Heat-activated. Dry with hair dryer. Use straightening iron for longer lasting results. This serum is artificial colorant free, and alcohol free.
1Instrumental test after 4 uses of Smooth Transformer. ²Instrumental tests with routine 4 times of Shampoo + Smooth Transformer + Leave-on. ³ Consumer test on 68 participants, 1 application/week for 4 weeks. Based on a 15-day break observation. 4Instrumental test after 1 application of shampoo, mask & serum. 5Instrumental tests, with full routine after 4 uses of the Smooth Transformer. 6Instrumental tests.
Reprograms hair for up to 2 weeks of frizz control1
•\tUp to 5x smoother hair and 2x less frizz2
•\tControls unwanted volume for daily styling in half the time3
Keratin Alpha Sleek Mirror Sleek Serum, formulated with Keratin Sealer 5%. The Mirror Sleek serum seals the hair's keratin structure to:
•\tDelivers instant shine that lasts up to 5 days.4
•\tThe serum helps to fight against up to 80% humidity5
•\tHeat protection up to 230°C (450°F)6
Heat-activated. Dry with hair dryer. Use straightening iron for longer lasting results. This serum is artificial colorant free, and alcohol free.
1Instrumental test after 4 uses of Smooth Transformer. ²Instrumental tests with routine 4 times of Shampoo + Smooth Transformer + Leave-on. ³ Consumer test on 68 participants, 1 application/week for 4 weeks. Based on a 15-day break observation. 4Instrumental test after 1 application of shampoo, mask & serum. 5Instrumental tests, with full routine after 4 uses of the Smooth Transformer. 6Instrumental tests.
Directions
Shake before use. On washed and towel-dried hair, detangle and section hair into two parts. Spraying into your hand, start with 2-4 sprays for thin to medium hair and 6-8 sprays for thicker hair. Rub hands together and distribute product evenly from lengths to ends. Do not rinse. Heat-activated. Dry with dryer. Use straightening iron for longer-lasting results.
Ingredients
1261091 B2 - INGREDIENTS: DIMETHICONE • BIS-(MORPHOLINOMETHYL C1-4 DIALKOXYSILOXY) DIMETHICONE • BIS-CETEARYL AMODIMETHICONE • PARFUM / FRAGRANCE • LINALOOL • CITRONELLOL • GERANIOL (F.I.L. N70063363/1).
This list of ingredients may be subject to change, please consult the packaging of the product purchased.
Bundle
25% SAVING. When you buy two qualifying L'Oréal Professionnel products.*
*Simply add two qualifying L'Oréal Professionnel products fulfilled by SEPHORA UK to your Shopping Bag and the discount will automatically apply at checkout. One offer bundle per order. Valid until the 13th July or whilst stock lasts. Cannot be used in conjunction with any other promotional discount. Offer is not applicable to pending purchases or previously made purchases.
Free Gift
FREE Absolut Repair Molecular Mini Rinse-off Serum 75ml when you spend £38 on L'oreal Professionel.*
*One free gift per order. Valid until the 13th of July or whilst stock lasts. Your free gift will automatically add to the shopping bag page. Total at order summary must be £38 or more worth of L'oreal Professionel products, after any Promotion Code, Brands You Love discount and before delivery charges are applied. Cannot be used in conjunction with any other Promotion and this offer is not applicable to previously made or pending purchases.
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Rated 2 out of
5
by
MORGAN from
Stinky
It works.. my hair looks really good when using this but I can not get past the smell. It smells like burning tyres and liquorice and stays in your hair until the next wash. Absolutely disgusting smell.
Date published: 2026-06-21
Rated 5 out of
5
by
CharlotteD from
Smooth and sleek
[This review was collected as part of a promotion.] Ive recently used the L'Oréal Keratin Alpha Sleek Serum 50ml and I have to say I am really impressed with the results. From the first uses, I noticed a clear difference in the improvement of my hair, as it appears and feels much softer and sleeker.
Having afro hair, frizz has always been an issue for me, but after using this serum I have noticed a big difference especially in more humid weather.
My hair feels much more controlled throughout the day, but doesn't feel heavy or greasy and it's great that it lasts up to 10 weeks, however, I did reapply sooner to get the same effects. It also helps control volume perfectly, as my hair appears polished and styled, rather than puffy and frizzy.
Despite applying sooner, what I love most is the long lasting effects. With my hair care routine, I usually have to apply lots of products to try and reduce the frizz, however, with this product I have been able to use less products which means less chemicals on my hair, which can often make my hair feel cakey and greasy.
After numerous uses, I would definitely recommend the serum and I will definitely be repurchasing again. I have already recommended it to family and friends, especially my curly hair girls.
Date published: 2026-04-07
Rated 3 out of
5
by
LindsayF from
Use a small amount
[This review was collected as part of a promotion.] I found this L’Oréal serum to leave my hair sticky and unmanageable. So after trying it and using a lot less it was slightly less sticky and kept my hair straight and manageable for longer than normal. I had shine and lot less frizz than usual .
Date published: 2026-03-27
Rated 4 out of
5
by
MeganJ from
Great product for taming frizz and getting that sl
[This review was collected as part of a promotion.] Smooth, frizz free hair for up to 2 weeks with a lasting shine. Great for taming unruly hair and boosting manageability.
The spray aspect of the bottle is great as it’s mess free and the application couldn’t have been easier.
I have quite long hair at the moment and I used around 8-10 sprays. So this bottle will last quite a while
Date published: 2026-03-27
Rated 4 out of
5
by
NayhaaS from
Good but don’t like the smell
[This review was collected as part of a promotion.] I like how it works and it does truly smooth my hair but I’m not a big fan of the smell. It smells really strong and similar to bleach. Other than that it is good. I like the packaging too.
Date published: 2026-03-26
Rated 5 out of
5
by
CathyS from
Five days straight smooth hair ❤️
[This review was collected as part of a promotion.] L'Oréal professional keratin Alpha Sleek serum is a leave in serum for smooth, frizz free hair. Reprograms the hair for long lasting frizz control. Glass shine and easier styling in half the time. The serum seals the hairs keratin structure for up to 5 days straight smooth hair. Fights against 80% humidity and doubles up as a heat protectant too! The serum is heat activated with either a hair dryer or a straightener for long lasting results. Just divide the hair into sections, spray the serum into your hands and glide through sections until hair is coated before heat styling for best results. I used a straightener and I can definitely see a huge difference. My hair felt significantly smoother, easier to style and did last days before I needed a wash day! I love that the serum is colourant and alcohol free. Easier manageable glossy hair, an amazing serum ❤️
Date published: 2026-03-24
Rated 5 out of
5
by
IsabelliT from
perfect for a straight look with no frizz
[This review was collected as part of a promotion.] great serum and works best with heat for a glossy look. Worth it’s value as a little goes a long way. Makes your hair smell light and salon-fresh.
Apply to damp hair, don’t rinse, and style with heat.
Date published: 2026-03-23
Rated 5 out of
5
by
LeahR from
Easy to use
[This review was collected as part of a promotion.] Such an easy product to use, simply wash my hair and then spray onto it after. No harsh smells, good sized bottle, pretty purple colour so looks very nice. Heat activated so tends to work when using the hairdryer after washing.
Date published: 2026-03-09
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