Workplace-specific bronchial challenge and occupational asthma due to persulfate salts.

Provocación bronquial específica en el trabajo y asma ocupacional por sales de persulfato To the Editor: Persulfate salts are the agents most commonly associated with occupational asthma (OA) among hairdressers. 1 Although the first cases were described decades ago, the prevalence, mechanism, value of diagnostic tests and the progress of these patients remain poorly defined. We present the case of a hairdresser with respiratory symptoms associated with exposure to persulfate salts in whom a specific bronchial challenge (use or exposure test) performed in the workplace was useful for confirming the diagnosis of OA. A 30-year-old woman who began working as hairdresser at the age of 20. Rhinitis and bronchial asthma in childhood, subsequently asymptomatic. She presented with asthma, onset one year previously and poor control despite treatment. She had had several exacerbations while at work, requiring hospital care, for which reason she was referred to the Respiratory Medicine department. Initial physical examination was normal. Of note on biochemistry was IgE 456 IU/ml. Specific IgE (RAST/CAP method) was positive for Dermatophagoides farinae, Dermatophagoides pteronyssinus, Felis domesticus, Canis familiaris and Olea europea. Fig. 1. Specific bronchial challenge in the workplace: monitoring of lung function during work showed a fall in FEV1 >20%. FEV1%: percentage compared to predicted forced expiratory volume in first second; post: post-bronchodilator FEV1; pre: baseline FEV1. Paranasal sinus and chest X-rays showed no pathological findings. Spirometry results were normal with FVC 3250 ml (94%), FEV1 2670 ml (97%) and FEV1/FVC 82, and post-bronchodilator test was negative. A non-specific bronchial challenge test was performed with increasing methacholine concentrations. FEV1 fell by 30% with a 1.56 mg/l dilution, corresponding to a PC20 of 1 mg/ml. Diur-nal variability in peak expiratory flow (PEF) over one month was greater than 20%. Correct treatment compliance adapted to her level of severity was confirmed, but the patient continued to show symptoms at work. She was asked again about the products she used and she indicated that it was the decolorizing agents that triggered the crises. The patient was asked to bring some along to the clinic and they were determined to contain persulfate salts. In view of suspected OA caused by persulfate salts, an " exposure test " was performed, consisting of monitoring lung function in her workplace using a portable spirometer. After baseline spirometry was shown to be normal, the patient began to use the bleaching agent as usual, lightening a client's hair (washing, …