Six rounds of investigations at 6-monthly intervals of ventilatory capacity, skin sensitivity and respiratory symptoms were carried out together with serological studies on a group of workers intermittently exposed to Bacillus subtilis derivatives containing proteolytic enzyme while compounding washing powder. 369 sets of readings of ventilatory capacity were made on seventy-seven males and 180 sets of readings on forty-one females. Overall, with change of employment and improvement in industrial hygiene, ventilatory capacity measurements improved.
Subjects who became prick test positive, as a group showed a decrease in the ratio of observed to expected FEV1 significantly greater than for the prick test negative group.
There was no significant excess of symptoms developing in the prick test positive group during the course of the survey though smokers and those with previous dust exposure had a higher number of symptoms than non-smokers and those not exposed to other dusts respectively.
A serological study of nine subjects initially prick test positive to B. subtilis who subsequently varied their skin reactions, showed them to have low levels of IgE and predominantly normal ventilatory capacities.