As these materials are formed by the self-assembly of polar lipids in aqueous conditions, their intermolecular arrangement is affected by changes in solution conditions, including changes resulting from microbial growth. This study demonstrates that monoolein-based lipid mesophases are susceptible to transformation from V₂→H₂ structure after exposure to live bacteria commonly found on the skin and nasal mucosa (S. aureus). The transformation has been attributed to enzyme-mediated hydrolysis, which takes place within an application-relevant timeframe (~8 h) and reduces drug release rates by 50%. These findings will inform the future development of these materials for transdermal applications.