La Mer's newest moisturizer, The Rejuvenating Night Cream, costs $450 and just won a 2026 Allure Best of Beauty Award. A reviewer who tested it for three weeks reports dry patches gone, softened fine lines and restored bounce — but the formula's headline ingredient remains a mystery even to cosmetic chemists.

What is in the $450 jar?

The star technology is MRA-3, which La Mer calls its "marine retinol alternative." The brand says the proprietary technology is designed to "enhance density, complement natural support polymers and speed cell renewal" without retinol-associated irritation.

Here's the catch: La Mer does not disclose what MRA-3 contains. "It's likely more accurate to think of it as being intended to provide some of the cosmetic benefits we associate with retinol—smoother, firmer, more youthful-looking skin—rather than assuming that it works through the same biological mechanisms as a retinoid," says Jenna Queller, MD, a board-certified dermatologist based in Boca Raton, Florida, who is not affiliated with the brand. That distinguishes it from better-characterized retinol alternatives like bakuchiol.

Cosmetic chemist Kelly Dobos, based in Cincinnati, identified Crithmum maritimum extract and Crithmum maritimum callus culture filtrate — both derived from coastal plants — as marine ingredients of interest. "There are studies that show potential benefits for collagen and skin renewal, but those experiments were conducted on cells or reconstructed skin rather than people," says Dobos.

Does the science hold up?

La Mer has some data. In a study of 31 people, the brand found the finished cream improved eight signs of aging, including fine lines, plumpness, firmness, smoothness, texture and wrinkles. The testing was small, however, and done on the complete formula, so there is no way to separate MRA-3's contribution from everything else in the jar.

The formula also contains:

• Miracle Broth: the brand's signature blend, made from sustainably harvested Giant Sea Kelp fermented for about four months; a few drops from each previous batch seed the next, creating a continuous lineage.
• Four peptides: palmitoyl tripeptide-1, palmitoyl tetrapeptide-7, palmitoyl hexapeptide-12 and acetyl hexapeptide-8. "The first two make up Matrixyl 3000, a popular peptide duo designed to support collagen and, over time, help skin look firmer," says Dr. Chang Son, a board-certified dermatologist based in New Jersey.
• Magnesium ascorbyl phosphate: "a vitamin C derivative that's generally more stable and potentially less irritating than pure L-ascorbic acid," says Dr. Queller, with "brightening potential," per Dr. Son.
• A moisturizing base: shea butter, glycerin, dimethicone, jojoba oil, mango butter and sodium hyaluronate. That lineup likely explains the instant blurring of fine lines — an effect "likely due to the hydrating elements of the formula rather than longer-term changes in the skin," says Dr. Son.

One caution: the cream contains perfume, eucalyptus oil, limonene and linalool. Someone with "eczema, rosacea, reactive skin, or a known fragrance sensitivity may be more likely to experience irritation," says Dr. Queller.

How does it perform in practice?

The texture looks buttery and thick — the jar can be held upside down without the cream budging — yet it melts on contact. A pea-size amount covers the whole face. After three weeks of nightly use, the reviewer had barely dented the two-ounce jar.

Despite the name, "there isn't anything inherently 'night-specific' about most of the ingredients in this cream," says Dr. Queller. Because MRA-3 is not retinol, La Mer does not flag sun-sensitivity concerns. Daytime wear proved impractical anyway: foundation pilled over the cream's slip.

The formula effectively combines the jobs of a vitamin C serum, peptide serum, barrier cream and retinol alternative in one product — a plausible explanation for the price. For consumers with resilient skin who want a minimalist nighttime routine, one jar replaces several bottles; those with fragrance sensitivity should look elsewhere.