Data for time trends in the prevalence of occupational asthma (OA) and rhinitis (OR) are not known. To investigate the prevalence and incidence of OA and OR over time. We chose to review studies on the prevalence and incidence of OA and OR due to laboratory animals (LA) as a marker of changing OA and OR patterns over time and analysed 15 cross-sectional and 4 longitudinal studies published from 1980 to 2006. The estimated prevalence of OA, defined as work-related chest symptoms (WRCS), declined from 8.2% in 1976 to 4.2% in 2001 (P < 0.005). When defined by WRCS and positive skin prick test (SPT) to LA, the estimated prevalence of OA was 6.7% in 1977 and 2.9% in 1999 (P < 0.02). The prevalence of OR, defined by WRNS or WRNS and SPT to LA, was not related to study date but was inversely associated with mean exposure duration. In four longitudinal studies no clear trend emerged over time. This review suggests a trend toward a progressive decline in the prevalence of occupational asthma due to laboratory animals, which may be due to the reduction of exposure since the early 1980s. A further reduction of exposure is needed to prevent the onset of occupational rhinitis.