These Smart Products Will Transform Your Hair While You Sleep

Most of us can't imagine our bedtime beauty routine without a slathering of hyaluronic acid serum, an exfoliating toner or a luxurious night cream. Skin experts argue that our skin cells regenerate faster while we're sleeping, so the products we choose to apply at this time have the potential to make all the difference. But while skin always takes centre stage in nighttime rituals, hardly any of us give thought to our hair.

Recently, there has been a rise in overnight hair serums, with the sole purpose of hydrating, reducing breakage and reversing the stress we put hair under during the day, for example over-brushing, using heated styling tools and subjecting it to environmental aggressors. But unlike the treatments you're used to, they won't completely drench your pillowcase.

So how important is overnight care for hair? "When we look at the processes in our body, there is a general consensus that at nighttime the body tries to repair itself and do all the maintenance overnight," said Steven Shiel, L'Oréal UK's director of scientific affairs. "When it comes to hair, it isn’t as clear because hair grows relatively slowly and there aren’t many studies to show that it really grows more overnight than it does in the day, but there is lots of anecdotal evidence," Steven continued. "If your body is working on its internal mechanisms at this time, then it is likely to focus on the hair, too. In fact, scientists are now starting to use samples of hair to measure people’s body clocks, by looking at how the hair follicle is reacting."

Lisa Caddy, trichologist at Philip Kingsley Trichological Clinic, elaborates: "While hair is never in 'repair mode' as it is essentially a dead tissue and so doesn't regenerate as skin would, hair cells are still dividing and growing while we sleep." To protect and strengthen these new cells, Steven suggests looking out for ingredients such as vitamin C, B5 and E, as well as iris root extract in haircare, essentially antioxidants. "These protect the protein matrix and give you long-term protection in hair," he explained.

If your hair feels parched and damaged thanks to over-styling, harsh weather or continuous colouring, swap sticky masks and oils, which can be uncomfortable to sleep in, for overnight serums. Lighter than most overnight haircare products, they can be applied from root to tip without weighing hair down and don't need to be rinsed out. Sachajuan's Overnight Hair Repair, £35, softens rough, damaged strands and imparts shine, while Shu Uemura Art of Hair Essence Absolue Overnight Serum, £35.90, minimises frizz and fluffy ends. Both can be applied to wet or dry hair.

If you can't be bothered to add yet another step to your bedtime beauty routine, that's okay. "Nighttime hair products are not entirely necessary," says Lisa, who explains that many in-shower treatments have the ability to penetrate the hair cuticle within 20-30 minutes of application. "Elasticizer, for example, provides hair with moisture, giving elasticity, bounce and shine," she continues. R29 also rates Redken All Soft Mega Sheet, £10.34 and Shea Moisture Jamaican Black Castor Oil Treatment Masque, £10.99. "Some people also find that sleeping on a silk pillowcase means hair is far less tangly and messy in the morning versus sleeping on cotton, for example," adds Lisa. "If hair is therefore less knotty it will take less effort to comb the hair, reducing further breakage."