K18 Leave-In Molecular Repair Hair Mask

Four minutes, no rinsing, and no conditioner beforehand. Those three things are the method.

1. Shampoo your hair. Do not use conditioner. Conditioner blocks the treatment from working.
2. Towel dry thoroughly — properly damp, not wet. Squeeze out excess water.
3. Apply a small amount evenly through the lengths and ends. Start with less than you think; this is a concentrated product.
4. Comb through so it is distributed evenly.
5. Leave it in for four minutes to activate.
6. Do not rinse. Style as usual, wet or blow-dried.

For the first few washes, use it every time you shampoo. After that, most people drop to every third or fourth wash to maintain the result.

Two practical notes:

• If your hair feels heavy or greasy, you used too much. Reduce the amount rather than rinsing it out.
• On very damaged hair the difference is usually obvious by the second or third use rather than the first.

For external use only. Avoid contact with the eyes. Keep out of reach of children.

K18 is built around a patented peptide designed to work inside the hair's internal structure rather than coating the surface. That is why it is left in rather than rinsed out, and why it does not build up or weigh hair down over time.

The product is free from silicones and heavy oils, which is what allows a leave-in treatment to avoid the greasy, coated feeling those ingredients cause.

The complete INCI ingredient list is printed on the packaging. Please read it before first use if you have a known allergy or a sensitive scalp.

Do I really not rinse it out?

Correct. It stays in. Rinsing removes the treatment before it has finished working and is the single most common reason people report no result.

Why can I not use conditioner first?

Conditioner coats the hair shaft and physically blocks the treatment from getting inside. Shampoo, towel dry, then apply.

Will it make my hair greasy?

Not if you use the right amount. It contains no silicones or heavy oils. A heavy or greasy feel almost always means too much product rather than the wrong product.

50ml or 150ml?

Start with the 50ml to see how your hair responds — it lasts longer than the size suggests. Move to the 150ml once you know it works for you, since it is better value per millilitre.

How often should I use it?

Every wash for the first few, then roughly every third or fourth wash to maintain.

Can I use it with Olaplex?

Yes. They work differently — Olaplex No.3 is a pre-shampoo treatment you rinse out, K18 is a post-shampoo leave-in. Use them at separate points rather than in the same wash.

• Product Type: Leave-In Hair Treatment
• Technology: K18Peptide™ Biomimetic Repair
• Use: Leave-in molecular repair mask
• Hair Type: All hair types
• 50 ml / 1.7 fl oz – Travel size or trial format
• 150 ml / 5 fl oz – Professional size for long-term use