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The Keratin Alpha Sleek smoothing treatment from L’Oréal Professionnel smooths unruly hair and, according to the brand, limits frizz for two weeks.
€23.35Price on Amazon.fr as of 15/10/2026 15:00Prices and availability are accurate as of the date and time indicated and are subject to change. Any price and availability information displayed on Amazon.fr at the time of purchase will apply to the purchase of this product.
Tame unruly hair with the L’Oréal Professionnel Keratin Alpha Sleek smoothing treatment. This Keratin Alpha Sleek transformative smoothing treatment smooths the hair at the keratin level. The brand claims two weeks of frizz control and hair that is easier to style.
Its patented technology combines Alpha-Bonder keratin and amino acids. The texture is fluid and creamy. Once a week, after shampooing with the range, apply 30 to 50 ml to towel-dried hair. Leave on for 10 to 15 minutes, then rinse. The Keratin Alpha Sleek smoothing treatment leaves hair soft, shiny and less puffed up by humidity.
The bottle holds 200 ml, enough for four to six treatments. This L’Oréal Keratin Alpha Sleek treatment is completed by the serum applied before straightening. It suits mainly wavy hair or hair that frizzes in humidity. The Keratin Alpha Sleek smoothing treatment softens the curl with each application.
Where it fits in your routine
WashShampoo
SmoothThis treatment, then rinse
StyleDrying, blow-drying
Made for
UnrulyFrizz
Rinse-out
Less frizz for 2 weeks
Review written by the Aura Capillaire team · Updated on 19 September 2026
We read buyers’ feedback on this Keratin Alpha Sleek smoothing treatment to pick out what comes up most often, good and not so good.
Where we land: for wavy hair or hair that frizzes in humidity, this is a simple smoothing treatment to do at home. For a complete routine, the shampoo and treatment duo below combines both steps. For more ideas, browse our hair care.
The same smoothing comes in several treatments in the Keratin Alpha Sleek range. Here is how this Keratin Alpha Sleek smoothing treatment compares with the three other most requested versions.
| Care | Use | Action | Best for |
|---|---|---|---|
| Transformative treatment L’Oréal Professionnel · this treatment |
10 to 15 min, rinse out | Smooths the keratin | Wavy hair |
| Smoothing mask L’Oréal Professionnel |
Mask | Anti-frizz | Dry hair |
| Mirror-smooth serum L’Oréal Professionnel |
Serum | Anti-humidity | Before straightening |
| Smoothing routine L’Oréal Professionnel |
Shampoo and treatment | Two weeks | Complete routine |
The Keratin Alpha Sleek smoothing mask nourishes deeply and also targets frizz. According to the brand, it reinforces the keratin. It does not promise the same two-week smoothing effect. The transformative treatment remains the key step for smoothing.
The Keratin Alpha Sleek mirror-smooth serum is applied before straightening to seal in the keratin. It protects against humidity and frizz. On its own, it does not transform the fibre. It extends the effect of the Keratin Alpha Sleek smoothing treatment.
The Keratin Alpha Sleek smoothing routine brings together the shampoo and this transformative treatment. It is the combination recommended by the brand. The budget is higher. If you already have the shampoo, the treatment on its own is enough.
Its smell is strong and reminiscent of a hair-removal cream. It can linger in the hair after drying. Rinse well and keep the product away from the eyes.
It works best on wavy hair or hair that frizzes in humidity. On very curly hair, the effect stays light. It softens the curl with each treatment.
The transformative treatment is left on for 10 to 15 minutes once a week to smooth. The mask nourishes and tames at every wash. The two complement each other.
Find more treatments to tame your hair in our leave-in treatments range.
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As an Amazon Associate we earn from qualifying purchases.
| Capacity | 200 ml |
|---|---|
| Brand | L'Oréal Professionnel Paris |
| Collections | Find this product in our collections: |
The same smoothing comes in several treatments in the Keratin Alpha Sleek range. Here is how this Keratin Alpha Sleek smoothing treatment compares with the three other most requested versions.
| Care | Use | Action | Best for |
|---|---|---|---|
| Transformative treatment L’Oréal Professionnel · this treatment |
10 to 15 min, rinse out | Smooths the keratin | Wavy hair |
| Smoothing mask L’Oréal Professionnel |
Mask | Anti-frizz | Dry hair |
| Mirror-smooth serum L’Oréal Professionnel |
Serum | Anti-humidity | Before straightening |
| Smoothing routine L’Oréal Professionnel |
Shampoo and treatment | Two weeks | Complete routine |
The Keratin Alpha Sleek smoothing mask nourishes deeply and also targets frizz. According to the brand, it reinforces the keratin. It does not promise the same two-week smoothing effect. The transformative treatment remains the key step for smoothing.
The Keratin Alpha Sleek mirror-smooth serum is applied before straightening to seal in the keratin. It protects against humidity and frizz. On its own, it does not transform the fibre. It extends the effect of the Keratin Alpha Sleek smoothing treatment.
The Keratin Alpha Sleek smoothing routine brings together the shampoo and this transformative treatment. It is the combination recommended by the brand. The budget is higher. If you already have the shampoo, the treatment on its own is enough.
Review written by the Aura Capillaire team · Updated on 19 September 2026
We read buyers’ feedback on this Keratin Alpha Sleek smoothing treatment to pick out what comes up most often, good and not so good.
Where we land: for wavy hair or hair that frizzes in humidity, this is a simple smoothing treatment to do at home. For a complete routine, the shampoo and treatment duo below combines both steps. For more ideas, browse our hair care.
Its smell is strong and reminiscent of a hair-removal cream. It can linger in the hair after drying. Rinse well and keep the product away from the eyes.
It works best on wavy hair or hair that frizzes in humidity. On very curly hair, the effect stays light. It softens the curl with each treatment.
The transformative treatment is left on for 10 to 15 minutes once a week to smooth. The mask nourishes and tames at every wash. The two complement each other.
Find more treatments to tame your hair in our leave-in treatments range.
Quality products • Responsive customer service • Excellent value for money
