Background: Preservatives represent one of the main causes of skin irritation and contact allergies.
Aims: To comprehensively evaluate the skin irritation potential of phenoxyethanol, methylparaben, propylparaben, imidazolidinyl urea, and DMDM hydantoin under regulatory acceptable concentrations.
Methods: A patch test and repeated open application test (ROAT) were applied to evaluate skin irritation in vivo. In vitro alternative methods consisting of the keratinocyte cytotoxicity assay, red blood cell (RBC) test, and hen's egg test-chorioallantoic membrane (HET-CAM) were performed to elucidate the mechanism of preservative-induced irritation responses.
Results: The patch test showed that all test substances showed a weak erythema response. Propylparaben had the highest occlusive irritancy potential in the patch test, owing to damage to the cell membrane. The two formaldehyde releasers showed noticeable skin irritation potential in the ROAT through their cytotoxicity to keratinocytes, while a visible response was observed after applying phenoxyethanol and the two parabens. No filtration was noticed in the in vivo tests, which might be attributed to the failure of subcutaneous vessel alteration by the preservatives.
Conclusions: Commonly used cosmetic preservatives have minor skin irritation potential with mild erythema reaction under practical use, especially formaldehyde releasers and propylparaben.
Keywords: alternative methods; preservatives; regulatory acceptable concentration; skin irritation.
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