In the United Kingdom, laboratory animal allergy (LAA) has been recognized as an important occupational disease for nearly 25 years. However, introduction of health and safety legislation (e.g., the Control of Substances Hazardous to Health Regulations of 1988) and an increasing knowledge of the factors that contribute to the etiology of this disease have had surprisingly little impact on the prevalence and incidence of LAA over the last 10 to 20 yr. Studies of the relation between exposure to animal allergens and the development of LAA reveal that the risk of disease increases with increasing intensity of exposure. Current evidence suggests that animal allergens are very potent, and substantial decreases in allergen exposure are therefore necessary before a reduction in symptoms will be observed. In the United Kingdom, it is unlikely that an Occupational Exposure Limit will be set for animal allergens in the near future, partly because an adequately standardized assay for quantifying exposure is not yet available. Prevention of LAA in the future will probably be driven by the needs of the industry and will most likely rely on the adoption of guidelines describing " best practise" which incorporate sophisticated engineering methods of controlling exposure to animal allergens.