Dermal Effects: Skin Barrier Interactions and Irritation Potential

Dermal exposure is an important consideration in the safety evaluation of nanocellulose materials (NCMs), including cellulose nanofibrils (CNFs, also referred to as cellulose nanofibers) and cellulose nanocrystals (CNCs), as their use expands across consumer, industrial, and biomedical applications. This chapter provides an integrated assessment of skin permeation and barrier interactions, cytocompatibility, and irritation potential, synthesizing evidence from the published literature with findings from studies commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Studies using cultured skin cells and reconstructed human epidermis models consistently show that CNFs and CNCs exhibit low cytotoxicity under typical exposure conditions and do not induce skin irritation when evaluated in accordance with OECD Test Guideline (TG) 439. Although surface chemistry, material form, and other material-specific factors may influence cellular responses, no significant adverse dermal effects have been reported. NEDO studies using 3D cultured human skin models demonstrated that TEMPO-oxidized CNFs remained confined to the outermost skin layers, with no detectable penetration into deeper tissues or receptor fluid. Overall, current evidence suggests a low potential for adverse dermal effects under realistic dermal exposure scenarios, while highlighting the importance of material-specific evaluation for prolonged skin contact.