Ethosome formulation of contact allergens may enhance patch test reactions in patients.

Ethosomes and liposomes are ultra-small vesicles capable of encapsulating drugs and cosmetic ingredients for topical use, thereby potentially increasing bioavailability and clinical efficacy. So far, few reports have suggested that formulation of cosmetic ingredients in vesicular carrier systems may increase the allergenicity potential. To investigate the effect of ethosome formulation of isoeugenol and methyldibromo glutaronitrile on the elicitation response under patch test conditions and by repeated open applications. A total of 27 volunteer patients with a previous positive patch test reaction to either isoeugenol or methyldibromo glutaronitrile were included in the study. In all patients, a serial dilution patch test was performed with the allergen in question formulated in ethosomes and in an ethanol/water solution. In addition, a repeated open application test (ROAT) was performed in a subset of 16 patients, and lag time until a positive response was recorded. Both contact allergens encapsulated in ethosomes showed significantly enhanced patch test reactions as compared with the allergen preparation in ethanol/water without ethosomes. No significant difference in the median lag time was recorded between preparations in the ROAT. Encapsulating potential contact allergens in ethosomes may increase the challenge response as compared with the same concentrations in an ethanol/water base without ethosomes.