Computational histology reveals that concomitant application of insect repellent with sunscreen impairs UV protection in an ex vivo human skin model.

Summary

Using NoxiScore, a deep learning-based computational histology pipeline, the authors identified nuclear texture features linked to UV-induced skin damage and showed that sunscreen protected ex vivo human skin whereas concurrent application with an insect repellent significantly reduced UVB protection. Repellent alone had no protective or toxic effect; inter-donor variability was observed.

Key Findings

• A deep learning pipeline (NoxiScore) quantified nucleus-related features indicative of UV/oxidative damage in human skin histology.
• Sunscreen alone protected against UVB damage ex vivo; repellent alone showed neither protective nor toxic effects.
• Concurrent sunscreen–repellent application significantly reduced UVB protection; protection levels varied across donors.
• Identified a texture-based nuclear feature as a quantitative biomarker of tissue damage.

Clinical Implications

Advise against simultaneous application of insect repellent and sunscreen on the same skin area; consider staggering application (e.g., apply sunscreen first, allow absorption, then repellent) pending in vivo validation. Digital morphometry tools like NoxiScore could augment preclinical screening of topical combinations.

Limitations

• Ex vivo model may not fully capture in vivo pharmacokinetics, sweat/sebum dynamics, or behavioral factors.
• Limited to selected products/actives; mechanism of interaction and generalizability to other repellents/filters need testing.

Future Directions

Conduct controlled in vivo studies to validate the interaction, optimize application sequences/intervals, and expand testing across repellent actives (e.g., DEET, picaridin) and sunscreen filters.