While seated for a showing of Are You There God? It's Me, Margaret. last weekend, I was reminded of how isolating the feeling of a changing body can be. It can start as being the first of the friend group to hit puberty and then, later in life, realizing that your once-full head of hair is dwindling while everyone else’s looks fuller. But as we learned in middle school, what feels entirely individual often isn’t — we just don’t really talk about it.

Hair loss, as “woe is me” as it might seem, will likely affect up to 50 percent of women, according to a 2022 study, with celebrities including supermodel Rosie Huntington-Whiteley and actress Alyssa Milano having shared their experiences with it. Luckily, as we’ve become more open about the “taboo” topic, haircare brands have created products designed to reverse it. And right now, one serum shoppers claim promotes growth in as little as one week is on rare sale at Amazon.

Shop now: $69 with coupon (Originally $86); amazon.com

Act+Acre’s Cold Processed Stem Cell Serum is 20 percent off at Amazon now through May 14. The scalp serum, which boasts nearly 1,000 five-star ratings at the brand’s site, promotes hair growth, reduces loss, and soothes the scalp thanks to the utilization of plant cell culture technology. The all-star ingredient of the serum is swiss apple stem cells, which Act+Acre founder and trichologist Helen Reavey once told InStyle, “are clinically proven to stimulate hair growth.” She explained that “when added to your scalp care routine, this unique ingredient elongates the process in which the hair sprouts from the follicle…[leading] to an increased amount of hair follicles and longer hair."

In addition to being science-backed, the scalp serum is also shopper-loved, with customers raving about their new growth and “shinier and silkier” locks. “[I] have been using this product every day for a week and [am] already seeing amazing results,” wrote one person, noting that they were “already seeing growth” after just seven days. Another shopper saw major differences after a month, including “at least a couple of inches” of growth as well as reduction in shedding, despite “always having [their] hair up.” And those with fine hair were particularly impressed by the treatment; one person wrote that, unlike most hair serums, this didn’t leave their hair greasy, sticky, or feeling weighed-down.

Not only is the scalp serum rarely on sale, but it’s gone through periods of being sold out for months, so grab Art+Acre’s Cold Processed Stem Cell Serum while it’s in stock and 20 percent off at Amazon.