Occupational Asthma Due to Hair Dyes Containing Para‐Amino Compounds

Background: Persulfate salts in hair bleaches are a well-documented cause of occupational asthma (OA) among hairdressers, but little information is available on OA caused by hair products containing other low-molecular-weight chemicals. The aim of this study was to investigate the prevalence and clinical characteristics of OA caused by oxidative hair dyes containing para-amino compounds (PACs). Methods: This retrospective multicenter study was conducted among 98 hairdressers with OA ascertained by a positive specific inhalation challenge (SIC) with hair products completed between 2006 and 2018 in 14 European tertiary centers. Nine hairdressers (9%) with a positive SIC response to hair dyes containing PACs were identified and reviewed. Results: Eight hairdressers developed a bronchial response during “work-simulation” SICs with hair dyes used at work, whereas one subject was challenged with pure para-phenylene diamine. The pattern of bronchial reactions was isolated late, dual, and isolated early in four, three, and two subjects, respectively. A significant post-challenge increase in nonspecific airway hyperresponsiveness was detected in three of the seven (43%) subjects with both pre- and post-SIC measurements available. Among subjects with fractional exhaled nitric oxide measurements (n = 3) or sputum eosinophil counts (n = 4) available both before and after the SIC, none showed a significant increase in these airway inflammatory markers. Conclusions: Hair dyes containing PACs may contribute substantially to OA among hairdressers. This possibility should be considered carefully when evaluating hairdressers with work-related asthma symptoms. However, there is a need for further investigation of the underlying inflammatory and immunological mechanisms.