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The concept of hyaluronic acid in hair-care products isn't a new one. According to cosmetic chemist David Petrillo, when it shows up in shampoos and conditioners, hyaluronic acid binds to the strands and follicles encourage a smoother look and feel and help prevent breakage. But using a straight-up hyaluronic acid serum intended for the skin seems a little strange, no? Not to mention potentially wasteful if it's not effective. But that didn't stop one TikTok user from experimenting and sharing her results with what has become an audience of hundreds of thousands of viewers.
On August 29, Kaitlyn Boyer posted a video with the caption, "Saw a TikTok that said hair oil doesn't moisturize your hair, only water can. So I tried Hyaluronic Acid!" In the clip, we see her dry-looking blonde ends before she wets her hair and applies The Ordinary's Hyaluronic Acid 2% + B5. The $7 skin-care serum is made with a mixture of different molecular weights of hyaluronic acid — not to mention vitamin B5 — to help replenish moisture and support the skin barrier.
Boyer says she felt a "major difference" after just two nights of use. After two weeks, her hair looks noticeably softer, and she says it's "way more manageable."
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It sure looks like a hyaluronic acid serum indicated for skin could be a boon for hair. But can hyaluronic acid serum really moisturize hair? Yes and no.
"Hyaluronic acid is a humectant, and rather than moisturizing hair, it works by drawing moisture in from the environment," says Connecticut-based board-certified dermatologist Deanne Mraz Robinson. "When applied to damp hair, HA can hold approximately 1,000 times its weight in water."
And The Ordinary's Hyaluronic Acid 2% + B5 especially may make quite a bit of sense for hair. "It uses a combination of hyaluronic acid, hyaluronic acid crosspolymer, and B5, which does make sense for hair treatment," says cosmetic chemist Ginger King, who explains that the hyaluronic acid crosspolymer is a film former to seal in moisture.
The Ordinary Hyaluronic Acid 2% + B5
$7
Mraz Robinson suggests applying the HA serum to your scalp as a treatment so it can soothe and nourish dry skin. "Then brush your hair, spreading the serum down the hair shaft to the ends," she advises. "Leave it on for a few minutes — or if you're super dry, overnight — and then wash your hair as normal."
But don't toss your hair oil. Instead, Mraz Robinson says, use your favorite jojoba- or argan-based hair oil after the hyaluronic acid serum to retain more moisture, seal the cuticle, and fight frizz.