Kiehl's 1cc CollaShot Plumping Serum earned a 4.3-star average rating from 998 real-world testers, giving the brand its first consumer validation outside the lab for a product built around GLP-1 weight-loss skin changes.

The serum, which launched this summer at $55 for 30 mL and $78 for 50 mL, went to NewBeauty BeautyPass members through the Free Gift Friday program. A post-campaign survey, fielded October 1, 2026, reached 1,200 recipients by SMS; 998 members who actually used the product responded. Of those, 85.4 percent rated it four or five stars, and 62.6 percent said it works better than similar products on the market.

What makes the formula different?

Rapid weight loss, common among people taking GLP-1 medications, can visibly change the face: deflated cheeks, lost elasticity and thinner-looking skin. Most plumping serums rely on hyaluronic acid to draw water to the skin's surface. CollaShot takes another route.

The formula centers on recombinant collagen polypeptides — biosynthetic collagen fragments — delivered in supra-liposomes that Kiehl's says are engineered to penetrate 10 layers of skin. It also contains rhamnose, which targets visible signs of aging linked to collagen loss, and vitamin B12, a vegan colorant responsible for the gel's pink tint. The "1cc" refers to the recommended daily dose: two pumps, twice a day.

"Collagen is the main structural protein in the dermis and plays a critical role in maintaining skin firmness," said Dr. Jane Yoo, a dermatologist and Kiehl's brand partner. She noted that the serum "won't replace injectables, but it helps the skin stay resilient through the changes GLP-1 patients are experiencing."

Kiehl's ran clinical testing that included consumers prescribed a GLP-1 for weight management. In that group, cheek sagging improved by 22 percent at eight weeks. Across testers, skin plumpness improved threefold over the same period. In the brand's consumer study, 94 percent said their skin looked more radiant, 93 percent said it looked plumper and 90 percent said their facial contours looked more defined.

What did the 998 testers report?

The survey reached a largely cold audience: 66 percent of respondents had never heard of the serum before it arrived. Among those who had, social media was the most common source of awareness, at 12.2 percent.

The headline numbers:

• 49.8 percent gave it a perfect five stars — the most common rating. Only 2.1 percent rated it one or two stars.
• 62.6 percent said it performs better than similar serums, with 25.9 percent saying "much better." Only 1.2 percent said it was worse.
• 61.3 percent found nothing unappealing about it. The most common complaint was price, at 16.2 percent.
• Ease of use (48.5 percent), effectiveness (45.8 percent), Kiehl's reputation (44.6 percent) and texture (43.4 percent) led the appealing features.
• 70.1 percent said they are likely or very likely to buy it again.
• 67.8 percent rated their likelihood to recommend it 8 to 10 out of 10; a perfect 10 was the single most common score, at 36 percent.

Testers singled out texture and overnight results. "It sinks into my skin instead of sitting on top of it, and it doesn't interfere with my makeup," wrote Melissa T., 45–54. "When I use it at night, my skin looks fuller and more hydrated in the morning."

"I'm a 77-year-old woman with dry skin. CollaShot is an absolute wonder," wrote Diane B. "It has really made my skin's texture and plumpness [improve]. It has really made a difference in my skin's texture and plumpness."

Cassie H., 35–44, said the "lightweight and bouncy" gel "sinks in quickly without feeling sticky or heavy" and "wears beautifully under my cream makeup without pilling." Aura R., 45–54, said she owns roughly 100 serums but uses only about five a day — and CollaShot "always makes its way into my top five."

Does it appeal beyond GLP-1 users?

Skin care marketed to GLP-1 users is a growing category. CollaShot stands out on two counts: Kiehl's tested it on GLP-1 patients, and it uses biosynthetic collagen with a delivery system designed to reach below the skin's surface.

The survey suggests the audience may extend well beyond that group. The quoted testers range from their 30s to their 70s, report dry, oily, normal and combination skin — and all of them rated the serum five stars.

Kiehl's recommends applying it morning and night, and says clinical results were measured over eight to 12 weeks of twice-daily use. The brand positions it as a complement to in-office treatments, not a replacement — a framing that matters as GLP-1-adjacent skin care moves from niche claim to measurable repeat-purchase business.