For hair that frizzes, puffs up in humidity or looks rough and dull. Biolage lists it as best for medium to thick hair and suitable for colour-treated hair, and says it also reduces frizz and adds shine on curly hair.

It is an easy leave-in for everyday use at home. Anyone with very fine hair should start with a single pump on the ends so the lengths stay light.

Shampoo and conditioner can only start the smoothing; once hair is dry, humidity gets to work again. This serum is the step that stays on. The silicone base seals and polishes the surface, the micro-dose of camellia oil adds a humidity barrier, and glycerin keeps the strands from drying out, which is often why hair frizzes in the first place. Biolage measured 80% less frizz for up to 24 hours versus a non-conditioning shampoo, and because one pump goes a long way, a 100 ml bottle lasts.

Warm one pump of serum between your palms.

Run it through damp hair, starting at the ends and then working up through the lengths, and blow-dry.

For extra shine or to calm flyaways, smooth a small amount over dry hair.

Start with one pump and add more only if your hair needs it.

Pros:

• Up to 24 hours of frizz control from a small amount
• Works on damp hair before blow-drying and on dry hair as a touch-up
• Camellia oil adds a protective layer against humidity
• Suitable for colour-treated hair
• Pump dispenses a measured dose, so it is easy not to overdo it

Cons:

• Silicone-based (dimethicone, dimethiconol), so it does not suit a silicone-free routine
• Contains several fragrance allergens, such as geraniol, isoeugenol and citronellol, which can bother sensitive skin
• Made for medium to thick hair; too much on fine hair can look flat
• No temperature rating is given, so it is not a substitute for a dedicated heat protectant