Frizz, unwanted volume and long styling routines can make maintaining smooth hair at home difficult. L’Oréal Professionnel Keratin Alpha Sleek is a professional at-home smoothing range designed to help create smoother, softer and more manageable hair while controlling frizz and unwanted volume.

The complete Keratin Alpha Sleek routine includes four products:

Keratin Alpha Sleek Shampoo 300mL
Keratin Alpha Sleek Progressive Treatment / Smooth Transformer 200mL
Keratin Alpha Sleek Mask 250mL
Keratin Alpha Sleek Mirror Sleek Serum 50mL

But you don't simply apply all four products one after another.

The Progressive Treatment is used once a week, while the Mask is used instead of the Progressive Treatment on your other wash days. The Mirror Sleek Serum completes both routines before heat styling.

What is Keratin Alpha Sleek?

Keratin Alpha Sleek is L’Oréal Professionnel's smoothing and anti-frizz haircare range for people who want greater smoothness, softness, frizz control, volume control and easier styling.

It is suitable for all hair types, including natural and colour-treated hair. 

Despite the name, L’Oréal states that the products do not contain animal-derived keratin. The name refers to the range working at what L’Oréal describes as the hair's Keratin Alpha level

What are the benefits of Keratin Alpha Sleek?

When the complete routine is used as directed, Keratin Alpha Sleek is designed to help with:

• Smoother, softer-feeling hair
• Frizz control
• Unwanted volume control
• Increased shine
• Improved manageability
• Easier daily styling
• Protection during heat styling

L’Oréal reports up to two weeks of smoothness, frizz and volume control after four applications of the Shampoo + Smooth Transformer + Serum routine under its instrumental testing conditions.

How to Use the Keratin Alpha Sleek Range

There are essentially two Alpha Sleek routines.

Once a week: Progressive Smoothing Routine

Shampoo → Progressive Treatment → Serum → Heat Activation

Other wash days: Nourishing Smoothing Routine

Shampoo → Mask → Serum → Heat Activation

So you don't need to apply both the Mask and Progressive Treatment during the same wash.

Step 1: Keratin Alpha Sleek Shampoo 300mL

Start every Alpha Sleek routine with the L’Oréal Professionnel Keratin Alpha Sleek Shampoo.

This professional sulfate-free shampoo gently cleanses while helping smooth, soften and hydrate the hair. L’Oréal also describes benefits for shine, frizz and volume control. 

How to use

Apply evenly to wet hair.

Work into a lather and rinse thoroughly.

Then follow with either the Progressive Treatment on your weekly treatment day or the Mask on your other wash days.

Why use it?

Using the matching Shampoo keeps your cleansing step within the Alpha Sleek routine and prepares the hair for the smoothing or nourishing step that follows.

Shop L’Oréal Professionnel Keratin Alpha Sleek Shampoo 300mL – Second Avenue Hair

Step 2A: Keratin Alpha Sleek Progressive Treatment 200mL

The Keratin Alpha Sleek Progressive Treatment, also called the Smooth Transformer, is the key intensive smoothing step in the range.

Unlike a standard hair mask, this is a progressive treatment. L’Oréal recommends using it once a week, with performance building over repeated applications and peaking after four applications. Weekly use can then continue to maintain the results. 

How to use the Progressive Treatment

After shampooing:

1. Shake the bottle well.
2. Divide the hair into sections.
3. Apply the treatment evenly through the lengths and ends.
4. Use approximately 30–50g, depending on hair length and thickness.
5. Leave for 10–15 minutes.
6. Rinse thoroughly.
7. Follow with Keratin Alpha Sleek Mirror Sleek Serum.
8. Blow-dry completely to activate the smoothing technology.

L’Oréal says there is no benefit to leaving the Progressive Treatment on beyond the recommended 15-minute processing time. 

Benefits of the Progressive Treatment

The Smooth Transformer is designed to progressively improve:

• Hair smoothness
• Frizz control
• Unwanted volume
• Shine
• Manageability
• Styling time

L’Oréal reports 77% instant shine in instrumental testing and says the complete routine can reduce daily styling time following four applications under its testing conditions. 

Keratin Alpha Sleek Progressive Treatment – 200mL – Second Avenue Hair

Step 2B: Keratin Alpha Sleek Mask 250mL

The Keratin Alpha Sleek Mask has a different job.

You don't need to use it immediately after the Progressive Treatment.

Instead, L’Oréal recommends using the Mask on your other wash days, when you aren't using the Smooth Transformer. 

How to use

After shampooing:

1. Apply evenly through the lengths and ends.
2. Leave for 5 minutes.
3. Rinse thoroughly.
4. Follow with Mirror Sleek Serum.
5. Blow-dry and style.

Benefits of the Alpha Sleek Mask

The Mask provides the nourishing and moisturising component of the routine, helping:

• Hydrate the hair
• Nourish the hair
• Improve softness
• Improve smoothness
• Increase shine
• Control frizz and unwanted volume

L’Oréal's Australian professional information reports 61% more hydrated hair in instrumental testing of the Mask. 

Step 3: Keratin Alpha Sleek Mirror Sleek Serum 50mL

The Mirror Sleek Serum is the finishing product in the Alpha Sleek routine — and it's an important step.

This heat-activated leave-in serum is designed to help maintain smoothness while providing heat protection up to 230°C and anti-humidity protection under L’Oréal's testing conditions. 

How to use the Serum

After rinsing either your Progressive Treatment or Mask:

1. Towel-dry and detangle the hair.
2. Shake the serum before use.
3. Section the hair.
4. Spray the product into your hands.
5. Start with approximately 2–4 sprays for fine-to-medium hair or 6–8 sprays for thicker hair.
6. Rub your hands together.
7. Distribute evenly through the lengths and ends.
8. Do not rinse.
9. Blow-dry the hair completely.
10. For longer-lasting smoothing results, L’Oréal recommends following with a straightening iron. 

Benefits of Mirror Sleek Serum

• Heat protection up to 230°C
• Anti-humidity protection
• Frizz control
• Smoothness
• Volume control
• Helps support longer-lasting smoothing results
• Leave-in formula
• Heat activated 

SHOP: Keratin Alpha Sleek Mirror Sleek Serum 50mL

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Step 4: Heat Activation

Keratin Alpha Sleek is designed as a heat-activated routine.

After applying Mirror Sleek Serum, blow-dry the hair completely. L’Oréal also recommends a straightening iron for longer-lasting results. 

Always use heat tools appropriately for your individual hair condition and avoid unnecessary excessive heat.

Keratin Alpha Sleek Weekly Routine: An Easy Example

If you wash your hair twice per week, your routine could look like this:

Wash 1 – Progressive Treatment Day

Step 1: Alpha Sleek Shampoo
↓
Step 2: Progressive Treatment – 10–15 minutes
↓
Step 3: Rinse
↓
Step 4: Mirror Sleek Serum
↓
Step 5: Blow-dry and heat style

Wash 2 – Mask Day

Step 1: Alpha Sleek Shampoo
↓
Step 2: Alpha Sleek Mask – 5 minutes
↓
Step 3: Rinse
↓
Step 4: Mirror Sleek Serum
↓
Step 5: Blow-dry and style

Then repeat your Progressive Treatment once a week. 

Is Keratin Alpha Sleek Suitable for Colour-Treated Hair?

According to L’Oréal Professionnel, the Smooth Transformer is suitable for all hair types and both natural and colour-treated hair. 

However, individual hair condition still matters. Hair that is highly compromised, breaking or has an extensive chemical history may require personalised professional advice before adding intensive treatments or significant heat styling.

Is Keratin Alpha Sleek the Same as an In-Salon Keratin Straightening Treatment?

No.

Keratin Alpha Sleek is an at-home progressive smoothing system. It shouldn't be confused with a permanent hair straightening service or assumed to permanently change your natural hair texture.

Its purpose is to progressively improve smoothness and control frizz and unwanted volume when the routine is used as directed. 

How Long Does Keratin Alpha Sleek Last?

This is where the difference between how often you use it and how long the results can last is important.

L’Oréal recommends using the Progressive Treatment once per week.

After four applications of the Shampoo + Smooth Transformer + Serum routine, L’Oréal reports up to two weeks of smoothness, frizz and volume control under its testing conditions. 

So “up to two weeks” doesn't mean you initially use the treatment only once every two weeks. The recommended Progressive Treatment routine is weekly.

Does Keratin Alpha Sleek Actually Contain Keratin?

This is one of the most interesting things about the range.

Despite the name Keratin Alpha Sleek, L’Oréal says the products do not contain animal-derived keratin.

Instead, L’Oréal describes the technology as working at the hair's Keratin Alpha level, reshaping Keratin Alpha chains to create longer-lasting smoothness and frizz control. 

Keratin Alpha Sleek FAQs

How often should I use the Progressive Treatment?

Use the Smooth Transformer Progressive Treatment once a week after shampooing. L’Oréal says performance peaks after four applications and recommends continued weekly use for maintenance. 

Do I use the Mask and Progressive Treatment together?

No. Use the Progressive Treatment once weekly and the Mask on your other wash days. 

Do I use Mirror Sleek Serum after the Mask too?

Yes. The Serum is the leave-in finishing step used before heat styling as part of the Alpha Sleek routine. 

Do I rinse out the Serum?

No. Mirror Sleek Serum is a leave-in product. Apply it to towel-dried hair and then heat style. 

Does Alpha Sleek need heat?

Yes, if you're following L’Oréal's complete smoothing routine. The technology is heat activated. Blow-dry completely, with a straightening iron recommended for longer-lasting results. 

Can I use Alpha Sleek on coloured hair?

L’Oréal says the Smooth Transformer is suitable for both natural and colour-treated hair. 

Is Keratin Alpha Sleek suitable for all hair types?

L’Oréal states that the range is suitable for all hair types. Individual results will naturally vary according to hair type, condition, history and styling routine. 

Shop the Complete L’Oréal Professionnel Keratin Alpha Sleek Routine

Build your at-home smoothing routine with the complete L’Oréal Professionnel Keratin Alpha Sleek range at Second Avenue Hair:

1.Cleanse

L’Oréal Professionnel Keratin Alpha Sleek Shampoo 300mL – Second Avenue Hair

2. Weekly Progressive Smoothing Treatment

Keratin Alpha Sleek Progressive Treatment – 200mL – Second Avenue Hair

3. Nourish on Other Wash Days

Keratin Alpha Sleek Mask – 250mL – Second Avenue Hair

4. Finish & Heat Protect
L’Oréal Professionnel Keratin Alpha Sleek Mirror Sleek Serum 50mL – Second Avenue Hair

Used correctly, the range gives you a simple system: cleanse, progressively smooth or nourish, protect, then heat activate.