Influence of natural exposure to pollens and domestic animals on airway responsiveness and inflammation in sensitized non-asthmatic subjects.
BACKGROUND
Atopy may be a risk factor in the development of asthma. Indoor allergens are considered to be more potent asthma inducers than outdoor ones such as pollens. Lower airway inflammation may be present in non-asthmatic subjects during natural exposure to relevant allergens and may eventually lead to the development of asthma.


OBJECTIVE
To document seasonal variation in lower airway responsiveness and inflammation in sensitized non-asthmatic subjects, during natural exposure to allergens, and to determine whether it is more marked in those exposed to animals to which they are sensitized.


METHODS
Twenty-two atopic subjects were seen during and out of the pollen season. All (but the controls) were sensitized to domestic animals, and to trees, grasses or ragweed. Eleven were not exposed to animals at home and 8 were exposed. They were compared with 3 normal controls. A respiratory questionnaire was administered, allergy skin prick tests, spirometry, methacholine challenge, blood and induced sputum with differential cell counts were obtained during the pollen season for all subjects. These tests were repeated out of the pollen season.


RESULTS
Throughout the study, none of the subjects had asthma symptoms. Mean PC(20) was significantly lower in subjects exposed to animals compared with unexposed subjects or controls, both during and out of the pollen season. In season, subjects exposed to animals had significantly higher sputum eosinophil numbers than unexposed or normal control subjects.


CONCLUSIONS
Non-asthmatic atopic subjects show variable degrees of airway responsiveness and inflammation. However, subjects exposed to animals show higher airway eosinophilia, which may suggest they are at increased risk of developing airway hyperresponsiveness and asthma.
Boulay
Marie-Eve
ME
Centre de Recherche, Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Sainte-Foy, Québec, Canada.
Boulet
Louis-Philippe
LP
D000293:Adolescent; D000328:Adult; D016902:Air Pollution, Indoor / Q000009:adverse effects*; D000818:Animals; D000829:Animals, Domestic; D001249:Asthma / Q000175:diagnosis / Q000209:etiology; D016535:Bronchial Hyperreactivity / Q000175:diagnosis / Q000209:etiology*; D004781:Environmental Exposure / Q000009:adverse effects; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007249:Inflammation / Q000175:diagnosis; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D011058:Pollen / Q000009:adverse effects*; D011657:Pulmonary Eosinophilia / Q000175:diagnosis; D006255:Rhinitis, Allergic, Seasonal / Q000150:complications* / Q000175:diagnosis / Q000276:immunology; D012307:Risk Factors; D013183:Sputum / Q000166:cytology