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.