Three patients showed a positive SIC, two of them with the four-step protocol. Patient 5, who underwent a six-step SIC, showed a FEV₁ decrease of 18 % 2 h after the last inhalation step and was defined positive, too (overall 4 positive SICs). In all cases, the reaction was a late one (Fig. 1a). Patient 1 was diagnosed with occupational asthma due to persulfate 19 months earlier in another hospital, where she underwent a SIC with persulfate and showed a positive reaction. This positive reaction could not be reproduced with our test (overall 4 negative SICs).

The latency period (time between starting exposure and first symptoms) in SIC positive women (including patient 1) was 2 to 240 months and in SIC negative 12 to 24 months. Total exposure time was 60 to 264 months in SIC positive women and 16 to 84 months in SIC negatives. The only man (SIC positive) was exposed for 15 months and his symptoms appeared shortly after he had started to work. At the time of examination all but one patient took antiobstructive medication (Table 1). Work-related symptoms of the nose and skin were frequent (Table 2). Lung function testing was normal in all patients, but only two SIC negative patients did not show bronchial hyperresponsiveness.