Phenotypic Characteristics of Occupational Asthma Caused by Persulfate Salts in Hairdressers: A Multicenter Cohort Study

Background: The clinical and inflammatory characteristics of occupational asthma (OA) caused by persulfate salts (PS) in hair bleaches have not yet been comprehensively characterized. Objective: This study aimed to compare the phenotypic characteristics of PS-induced OA with those of OA due to other low-molecular-weight (LMW) agents. Methods: This study was conducted in a retrospective multicenter cohort of subjects with OA ascertained by a positive specific inhalation challenge (SIC). The clinical and inflammatory characteristics of hairdressers with PS-induced OA (n = 107) were compared with those of subjects who showed a positive SIC to isocyanates (n = 128) or various other LMW agents (n = 164). Results: Subjects with PS-induced OA had a longer duration of exposure to the offending agent before the onset of asthma than those with OA caused the other LMW agents. They reported more frequently work-related rhinitis (76%) and showed a lower post-SIC level of fractional exhaled nitric oxide (median, 18 ppb [25th-75th percentile, 13–26]) compared with OA caused by both isocyanates (36%, P < .001 and 35 ppb [21–80], P < .001, respectively) and the other LMW agents (53%, P < .001 and 27 ppb [14–52], P < .001). Subjects with PS-induced OA showed the highest rate of isolated late asthmatic reactions (49%), but the difference reached statistical significance only when compared with LMW agents other than isocyanates (31%, P < .002). Conclusions: The PS-induced OA is associated with a higher prevalence of work-related rhinitis and lower levels of fractional exhaled nitric oxide compared with OA caused by other LMW agents. These findings further indicate substantial phenotypic heterogeneity among this broad category of agents.