What does this research mean for the field?

Integrating the in vitro OECD TG439 assay with a stepwise human patch testing approach and predefined safety criteria provides a safe and practical method for evaluating skin irritation of cosmetic ingredients. Novelty: ClaimNovelty.METHODOLOGICAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

To establish and validate a stepwise skin irritation assessment strategy that links OECD Test Guideline 439 in vitro models to human patch testing without relying on animal assays.

September 5, 2026Journal of Applied Toxicology

A Stepwise Skin Irritation Assessment Approach Integrating in Vitro Skin Irritation Testing and Human Patch Testing

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To establish and validate a stepwise skin irritation assessment strategy that links OECD Test Guideline 439 in vitro models to human patch testing without relying on animal assays.
Evaluated OECD Test Guideline 439 (TG439) reproducibility across six laboratories using the LabCyte EPI-MODEL24 reconstructed human epidermis model to identify non-irritant concentrations for 17 substances.
Performed 24-hour human closed patch testing using stepwise concentration escalation to one-quarter and one-half of the TG439 non-irritant concentration, governed by predefined stopping criteria.
Inter-laboratory testing verified the reproducibility of the TG439 reconstructed human epidermis assay across six independent testing sites.
Most test chemicals produced Sugai's Irritation Index (S.I.I.) scores classified as 'Safe' or 'Acceptable' at both tested concentration tiers.
Specific surfactants, cationic preservatives, and hair dye intermediates yielded elevated S.I.I. scores that successfully prompted protocol-mandated discontinuation of dose escalation.

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Implication

Validation and human patch study demonstrates safe irritation assessment via stepwise concentration escalation, indicating an ethical testing framework for cosmetic ingredients.

Cite This Study

Ikeda et al. (2026) studied this question.

synapsesocial.com/papers/6a9bd4126b95aff0620eb5eb https://doi.org/10.1002/jat.70428

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Implication

Validation and human patch study demonstrates safe irritation assessment via stepwise concentration escalation, indicating an ethical testing framework for cosmetic ingredients.

A Stepwise Skin Irritation Assessment Approach Integrating in Vitro Skin Irritation Testing and Human Patch Testing

Key Points

Discussion

Implication

Cite This Study

A Stepwise Skin Irritation Assessment Approach Integrating in Vitro Skin Irritation Testing and Human Patch Testing

Key Points

Discussion

Implication

Cite This Study

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