The science
The five-ceramide approach in this formula reflects the current understanding of skin barrier lipid biology. The stratum corneum's intercellular lipids consist of approximately 50% ceramides, 25% cholesterol, and 15% free fatty acids, organized in lamellar structures. A paper published in the Journal of Investigative Dermatology has demonstrated that topical ceramide supplementation is most effective when it includes multiple ceramide species rather than a single type, as different ceramides play distinct roles in barrier organization.
Ceramides NP and NS form the backbone of the lamellar lipid structure, while ceramides EOP and EOS have long omega-hydroxy chains that anchor the lipid matrix to the corneocyte envelope. Ceramide AP contributes to the overall diversity of the lipid composition. A 2017 study in the International Journal of Cosmetic Science confirmed that multi-ceramide formulations containing cholesterol and fatty acids more effectively restore barrier function than single-ceramide products.
Phytosphingosine, included in this formula as both a free sphingoid base and in the caprooyl ester form, serves dual functions. As a ceramide precursor, it stimulates endogenous ceramide production through the de novo synthesis pathway. Additionally, phytosphingosine has demonstrated antimicrobial activity against Propionibacterium acnes and Staphylococcus aureus, providing skin-protective benefits documented in a 2006 study in Antimicrobial Agents and Chemotherapy.
The pairing with retinoids is scientifically rational. Retinoids increase epidermal cell turnover, which temporarily disrupts the lipid barrier. One trial published in the Journal of Cosmetic Dermatology (2014) showed that applying a ceramide-containing moisturizer after retinoid treatment significantly reduced retinoid-associated irritation (dryness, peeling, erythema) while maintaining the retinoid's anti-aging efficacy. This validates Medik8's recommended usage protocol of applying this cream after Crystal Retinal.
Acetyl glucosamine has been shown to inhibit melanin synthesis by blocking the conversion of protyrosinase to tyrosinase, as demonstrated in research published in Experimental Dermatology (2007). At sufficient concentrations, it provides mild brightening effects and stimulates hyaluronic acid production, adding a skin-renewal dimension to the formula's primary barrier-repair function.
References 4 ShowHide
- Multi-ceramide formulations and barrier function restoration — International Journal of Cosmetic Science (2017)
- Antimicrobial activity of phytosphingosine against skin pathogens — Antimicrobial Agents and Chemotherapy (2006)
- Ceramide moisturizers reduce retinoid-associated irritation — Journal of Cosmetic Dermatology (2014)
- Acetyl glucosamine inhibits melanin synthesis via tyrosinase pathway — Experimental Dermatology (2007)