What is hair serum?

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3 min read L'Oréal Professionnel Team
20/08/2026

What is hair serum FAQs

Should I use hair serum if I have naturally fine hair?

It's a common misconception that hair serum will weigh down naturally fine hair. Instead, it all depends on which serum you use and in what quantity. A serum formulated to repair and strengthen hair, like the Absolut Repair Molecular Serum, will actually give thicker, healthier-looking results. If your hair lacks volume, or quickly becomes greasy at the roots, focus your serum application on the lengths and tips, and only use a couple of drops.


If you're looking to actively thicken your hair, try the Serioxyl Denser Hair Serum from L'Oréal Professionnel, used in a three-month daily programme, to add density to the hair and achieve greater volume and thickness.

What’s the best hair serum?
As with any haircare product, finding the best hair serum depends on your hair type and concerns. If you're unsure about which serum will give you the best results, ask your L'Oréal Professionnel hairdresser. They will be able to diagnose your hair and suggest the most suitable hair serum to include in your haircare routine.

When should I start using hair serum?
If you've noticed your hair looks dull and lacklustre, it tangles and breaks easily, if you suffer from frizz or flyaways, or are a regular user of heated tools to straighten or curl your hair, serum could be your haircare solution. Many also find that hair serum is a must when it comes to humid weather, vacations, or any situation where frizz and flyaways can be a particular pain.

How often should I use hair serum?
There’s no set answer to how often to use hair serum, as this can vary depending on hair type and condition. Most hair serums work best when applied to damp hair, so we recommend using your chosen serum after your regular hair wash. To benefit from heat protection, use it every time you style or dry your hair.