The Middleton sisters are famed for their healthy and glossy locks.

London - With shoulder-length wavy locks that are prone to kink and frizz, I know all about bad hair days.

Heavy conditioners make my hair lank, straighteners flatten the life out of it and much of the time it simply won’t behave.

The problem, according to L’Oreal, is that I haven’t been treating my scalp well enough.

“The scalp is made of skin,” says Patricia Pineau, scientific communications director at L’Oreal. “And while we moisturise and use specialist creams on our face, neck, eyes and even feet, we are not in the habit of treating our heads in the same way.

“Women need to understand that the beauty of their hair relies on the quality of the skin on their scalp.”

To help treat it, L’Oreal has launched the world’s first product that uses the stem-cell technology found in skincare to improve the look, feel and quality of our hair.

Kerastase Initialiste contains plant stem cells and aims to nurture the skin around the surface of the hair follicles, which is where you’ll find some of the hair’s stem cells, which build and repair the hair. L’Oreal’s clinical studies have shown that using it three times a week for a month will deliver better overall hair quality, thickness and softness.

Unlike hair masques and intense conditioners, which simply nourish your locks from the outside in, the serum aims to help your hair grow stronger from the roots. I have been using the serum for a couple of weeks every time I wash my hair. I make around ten partings in my washed and towel-dried hair and drip four drops along each on to my damp scalp.

The serum is fresh-smelling and not too runny, but at first I couldn’t see how it would make that much difference. Yet even after just one application, my hair was easier to style - and looked smoother and shinier.

It will take another fortnight of diligent use to get the full results, but it is already my fail-safe route to a good hair day. - Daily Mail

* Initialiste, £40, Kerastase salons, 0800 316 4400.