Naureckas and Solway (Oct. 25 issue) discuss the treatment of mild intermittent and mild persistent asthma but do not discuss the importance of indoor allergens. Allergens not only are triggers of symptoms, but some are also regarded as causal factors in the development of the disease. Because they continuously induce allergic inflammation of the airways, allergens may be more important as a cumulative cause of bronchial hyperreactivity than as triggers of acute attacks. Furthermore, longitudinal studies have shown an accelerated decline in the forced expiratory volume in one second in older adults who are exposed to certain allergens. In other diseases that are caused by exposure to foreign substances, such as hypersensitivity pneumonitis, avoidance of exposure to relevant antigens is the first line of treatment. In asthma, environmental control measures to reduce exposure to indoor allergens should be considered a primary antiinflammatory treatment. Such measures should help to prevent the development of chronic airflow limitation and, therefore, reduce the need for further pharmacologic treatment.