Redken labels this leave-in as a regimen for demanding, processed hair. That means hair that has been coloured, lightened or regularly heat-styled and now shows it: breakage, split ends, roughness and frizz through the mid-lengths and ends.

It is a retail product for home use, with no mixing or salon application involved. It suits anyone who already uses the Acidic Bonding Concentrate Shampoo and Conditioner and wants a finishing step, or anyone who wants bond-care conditioning and heat protection from a single cream before styling.

Most leave-ins either condition or protect from heat. This one is built to do both while also carrying Redken's Bonding Care Complex, the same bond-care technology that runs through the Acidic Bonding Concentrate shampoo and conditioner, in an acidic, citric-acid formula aimed at hair weakened by colour, lightener and hot tools.

Because it stays in the hair, it keeps working through styling instead of rinsing away. That makes it the step that protects hair at the moment it is most exposed: under a blow-dryer or a flat iron.

• Shampoo and condition, ideally with Acidic Bonding Concentrate Shampoo and Conditioner.
• Apply the leave-in to clean, damp hair.
• Distribute through the lengths and ends.
• Do not rinse. Style as usual; it protects up to 230°C (450°F) when you use hot tools.

Start with a small amount on fine hair and add more only where the ends need it.

Pros

• Heat protection up to 230°C (450°F) is built in, so it replaces a separate thermal spray for most styling.
• Redken's breakage, smoothness and split-end results were measured with the leave-in used on its own, not only as part of the full regimen.
• The silicone-rich cream leaves processed hair noticeably slicker and easier to comb and style.

Cons

• Silicones and fatty alcohols can weigh down very fine or oily hair if too much goes near the roots.
• It contains several listed fragrance allergens, which matters for sensitive scalps.
• It is not silicone-free; anyone avoiding silicones, for example in a curly routine, would look at the Acidic Bonding Curls leave-in instead.