Natural Ceramide Confirms New Effect of Strengthening the 'Second Skin Barrier'

Rosette Co., Ltd. (Headquarters: Shinagawa-ku, Tokyo; President & CEO: Keiji Fujii), in joint research with Utsunomiya University, has revealed that natural ceramide, primarily composed of β-galactosylceramide, strengthens the function of tight junctions, the skin's 'second barrier,' in addition to the 'stratum corneum barrier enhancement through promotion of stratum corneum ceramide synthesis' that has been previously reported. These research results will be presented at the 125th Annual Meeting of the Japanese Dermatological Association.

Background of the Research

For many years, the skin's barrier function was thought to be centered on the 'stratum corneum barrier.' In the stratum corneum, the outermost layer of the epidermis, lipids centered on ceramides form a lamellar structure, responsible for moisture retention and protection from external stimuli. On the other hand, in recent years, it has become clear that 'tight junctions' present in the granular layer beneath the stratum corneum also play an important role as a skin barrier. Tight junctions act as a seal structure that tightly adheres cells together, preventing the invasion of foreign substances and irritants. However, until now, there have been limited reports showing that cosmetic ingredients can strengthen or protect the tight junction function itself.

Current Findings

In this study, analysis using human epidermal cells confirmed that natural ceramide increases the expression of tight junction-related molecules (such as Claudin-1 and Occludin) and strengthens tight junction barrier function. It was also confirmed that natural ceramide suppresses the decline in tight junction function caused by ultraviolet radiation. This indicates that natural ceramide may act as a bioactive lipid that strengthens not only the stratum corneum barrier but also the tight junction function, which is the second skin barrier mechanism.

Researcher Comment (Professor Genji Imokawa, Utsunomiya University)

'Until now, natural ceramide has been noted for its effect of increasing stratum corneum ceramides and improving the skin barrier. This study suggests the possibility that it also acts on tight junctions, the 'second skin barrier.' We believe this research is significant in showing that natural ceramide can potentially support both barriers simultaneously.'

Future Outlook

In atopic dermatitis and sensitive skin, a decline in not only the stratum corneum barrier but also tight junction function has been reported. This discovery is expected to lead to applications in sensitive skin care, skincare for atopic dermatitis, protection of the skin from UV damage, and countermeasures against age-related barrier decline. Furthermore, it could lead to a new skincare strategy of 'rebuilding the skin barrier mechanism itself,' rather than just conventional 'moisturizing by replenishing water.' Leveraging these findings, Rosette will continue to pursue research on the efficacy of natural ceramide for the skin and utilize it in product development.

≪Presentation Overview≫

Conference: 125th Annual Meeting of the Japanese Dermatological Association

Date & Time: June 12, 2026 (Friday) 9:10 - 10:10

Location: National Kyoto International Conference Center, Room 10 (1F Room C-2)

Presentation Title: β-Galactosylceramide Improves Epidermal Tight Junctions Damaged by UVB and AD