The subjects with negative skin tests were older, had a shorter duration of asthma, had lost more time from their usual activities, and had more frequent doctor visits than did the group with positive skin tests. When adjusted for age and duration of asthma, however, the 2 groups appeared similar with regard to asthma severity. No adjustment was performed for level of FEV,. Skin test reactivity declines with age, as does level of FEV,. It appears to be critical to adjust for these factors when the role of allergy in the severity of asthma in adults is assessed.
Cigarette Smoking
Cigarette smoking bears an intimate relationship to asthma. Smoking has important immunologic consequences; it may serve to sensitize specific individuals in the work environment to workplace exposures. Passive smoking may be the single most frequent workplace exposure. Finally, smoking may affect airway responsiveness directly or indirectly through its effect on level of FEV,.
It is unknown whether cigarette smoking increases asthma severity. It is now quite clear from a large number of clinical and epidemiologic investigations, however, that smoking increases airway responsiveness. Smoking may directly influence airway responsiveness by causing airway inflammation. Of greater interest in the context of occupational asthma is the role of smoking in predisposing to allergy.