Use of sorbitan sesquioleate in patch test preparations and patch testing with the substance—What do our results mean?

BACKGROUND: Sorbitan sesquioleate (SSO) is a sorbitan fatty acid ester, an emulsifier used in topical products and certain patch test preparations. SSO may affect the patch test results. It has been debated whether to include the substance in the baseline series to avoid misinterpretation of the results. OBJECTIVES: To report the prevalence and simultaneous reactions of SSO with other patch test preparations containing SSO as an emulsifier. MATERIALS AND METHODS: A retrospective analysis of 3539 dermatitis patients who underwent patch testing from 2016 to 2020 was performed. RESULTS: The 5-year SSO contact allergy prevalence was 0.48%, and 1.3% had a doubtful reaction. Patients with a stronger positive reaction (2+, 3+) were more likely to react simultaneously to other allergen preparations containing SSO (p value = 0.018). One patient with a strong reaction to SSO reacted positively to all SSO-containing patch test preparations. Definite fragrance allergens could not be identified in the patients who had simultaneous reactions to SSO and fragrance mix (FM) I. CONCLUSIONS: Patch testing with allergen preparations containing SSO affected the patch test interpretation. Fragrance contact allergy could not be ruled out when a patient simultaneously reacted to SSO and FM I. Changing emulsifiers in patch test preparations would be advantageous.