The first rule of environmental allergen control is that avoidance is appropriate for allergic patients with asthma. Although this rule is obvious to allergists, it frequently is not considered by families and physicians who are not trained in allergy. The next step in environmental avoidance is to determine the specific sensitivity of a patient. Clinically, practitioners have to address reduction of exposure to more than one allergen, and it is likely that the complexity of dealing with several treatment regimes decreases compliance.