Hair that has been weakened by colour, lightening, straightening or heat, and hair that is naturally coarse, dry or prone to frizz. Biotop positions it for damaged, fragile and chemically treated hair.

It is a retail salon product that is simple to use at home in the shower, and stylists also use it as an in-salon repair step. Anyone who dislikes an oily feel on the lengths can use it, since it is rinsed out.

Most hair oils sit on top of the hair as a finish. This one works the other way round: it is applied to wet hair after shampoo, turns creamy when warmed in the hands, and is rinsed out after a short wait, so it acts more like a concentrated mask than a serum.

That makes it a practical weekly repair step for hair that feels rough and brittle from colour or heat but goes limp under heavy masks. The keratin and kale pairing is what the whole 700 line is built on, so it slots in naturally with the 700 Keratin & Kale shampoo and conditioner.

• After shampooing, dispense the required amount into your palms.
• Rub your hands together until the oil turns into a creamy texture; warming it this way activates the formula.
• Apply evenly from the scalp through to the ends and massage gently.
• Leave on for 2 to 3 minutes, then rinse thoroughly.
• Use once a week, or whenever hair needs intensive repair. Follow with your usual conditioner or styling products.

Pros

• Rinses out, so it repairs without leaving the lengths greasy or weighed down
• Hydrolyzed keratin targets the rough, frizzy feel of chemically treated hair
• Quick: two to three minutes in the shower
• Free of sulfates, parabens and sodium chloride and safe on colour

Cons

• Only 30 ml, so long or thick hair goes through a bottle quickly
• Denatured alcohol is the first ingredient, which some people with very dry hair prefer to avoid
• Contains fragrance allergens (hexyl cinnamal, linalool)
• Not a leave-in finishing oil; it does nothing for shine between washes