Reactivity to sorbitan sesquioleate affects reactivity to fragrance mix I

Summary Background Fragrance mix I (FM I) and its single constituents contain 5% and 1% sorbitan sesquioleate (SSO), respectively. SSO is a rare sensitizer and a potential irritant. Objectives To determine whether the outcome of the FM I breakdown test is affected by positive patch test reactivity to SSO. Methods A retrospective analysis of data from the Information Network of Departments of Dermatology, 1998–2013, was performed. Results The full FM I breakdown test including SSO was tested in 2952 patients. Of these, 154 (5.2%) had a positive patch test reaction to SSO 20% pet. and 2709 (91.8%) had a negative patch test reaction. Positive reactions to one or more of the single fragrances contained in the mix were significantly more common (82.5% versus 57.3%) in SSO‐positive patients, who also had more multiple reactions than FM I‐positive patients with negative SSO reactions (61.5% versus 21.3% patients with reactions to two or more fragrances). Conclusions Our results indicate that reactivity to SSO markedly affects the outcome of patch testing with FM I and its single constituents. SSO must be an obligatory part of the full FM I breakdown test, and should ideally be included in the baseline series.