There she got about a hundred injections and, a week later, saw the beginning of the glow she’d sought. At home, “friends kept telling me, ‘Wow your skin looks so good,’ ” Yip says.

The injectable Rejuran is not FDA-approved and is available in America only for topical use, but that’s not stopping American women from traveling overseas, mostly to South Korea, to get it injected, for up to $450 a session. The company recommends three sessions, with results meant to last for up to a year.

Unlike other popular injectables, such as Botox which freezes muscle contractions, or fillers like Juvederm that pump volume into the skin, Rejuran purports to both hydrate the skin and boost its elasticity.

Women travel overseas and pay up to $450 a session to get Rejuran injections.

Rejuran is made with PN, a chain of molecules that contains fragments of DNA derived from salmon cells that are said to promote healing and skin regeneration. It originated in 2014 in South Korea, and 20 additional countries have approved its use as an injectable since then.

Parent company PharmaResearch has a number of other aesthetic drugs and devices in its portfolio, but, according to Forbes, Rejuran’s success in particular made founder and chairman Jung Sang-soo a billionaire this year. The company said it couldn’t confirm this valuation.

Some American doctors remain skeptical of Rejuran. “If it does work that would be great because everyone is looking for a booster that truly improves skin integrity, something that’s currently missing from the market, but anecdotal is not data, and the data we do have is still very new,” says Catherine Chang, a plastic and reconstructive surgeon in Beverly Hills. She has also heard mixed reviews—some people notice a big improvement in skin texture while others see none—and points out that side effects can include irritation, rash and skin discoloration.

PharmaResearch said it’s observed only minor skin reactions since Rejuran’s launch and no severe adverse side effects. The company said it has filed an application for FDA approval for injections.

“My main skin concerns were dryness, dullness and early fine lines,” says Tris Vo, a 25-year-old nurse in Toronto who went to Seoul to try Rejuran. The injectable is approved in Canada but costs about half as much in Seoul. “I began seeing results around day eight. My skin felt plumper, and I noticed a natural glow, fewer breakouts and my dry patches had disappeared.”

South Korea has long been a mecca for skincare enthusiasts, and part of Rejuran’s success is due to a broader interest in Korea-born beauty products and rituals (K-beauty for short). “Asian skincare overall tends to be much more advanced than in the U.S.,” says Chang. “K-beauty in particular may just be more noticed now than in the past because of the rise in popularity of K-pop, K-dramas and social media allowing users to see what everyone in Asia is doing.”

Alex Cho, a 34-year-old advertising director in Los Angeles, traveled to South Korea to get laser treatments for hyperpigmentation, but also tried Rejuran after hearing about its collagen-boosting effects. “My skin just looked more radiant, and it felt supple and silky,” she says of the result.

In the U.S., Rejuran is only legally offered as a serum or cream, usually as part of what’s called a “salmon facial” because it’s made of salmon-derived DNA fragments, which closely resemble human cells and are said to help stimulate collagen.

The salmon facial has been praised by Jennifer Aniston and Kim Kardashian and involves microneedling or a resurfacing laser, like Fraxel, followed by a topical application of Rejuran.

Unlike Botox or fillers which are injected sparingly and directed deep into the skin, Rejuran involves hundreds of shots near the surface “using a serial puncture technique,” says Chris Lee, head of global healthcare at PharmaResearch. “On average this results in 100 to 150 injection points per session.”

With any injection there is potential for infection, says Connie Yang, a cosmetic dermatologist in Manhattan.

Rejuran injections are also often combined with other treatments (collagen-stimulating filler Juvelook, ultrasound tightening device Ultherapy, and many lasers are frequently recommended by clinics) which can make it hard to isolate which intervention is impacting the skin.

Michelle Lee, the former editor of Allure magazine, combined full-face Rejuran with a trio of lasers and Juvelook on a recent trip to South Korea. “Within ten days my skin looked f—ing amazing, very glowy, and somehow poreless, and for the first time in years I did not need a spot of foundation or concealer,” she says, adding that she can’t be sure which treatment was responsible for the improvement.

Immediately after Rejuran the skin is covered in raised red, hive-like bumps, which have also been extensively chronicled on social media. It can take anywhere from 24 hours to a few days for them to disappear.

Lee says the experience is not for the faint of heart. “I have gone through childbirth three times, torn my ACL, and done microneedling with a derma pen,” she says. “I pride myself on having a pretty high pain tolerance, but this was intense.” Clinics usually offer topical numbing cream or anesthesia during the treatment.

Sofie Pavitt, a New York facialist who has, by her own admission, tried it all, including Rejuran in Seoul earlier this year, agrees. “I stopped counting after 80 shots,” says Pavitt. “It’s not unbearably painful, but it’s like death by 1,000 cuts.”

“When you walk out you look really nuts,” she says. “It’s giving ‘Avatar.’”