Background: Exposure to indoor allergens play a major role for development of sensitization and induction of allergic inflammation, bronchial hyperreactivity and symptoms in sensitized individual.
Objective: fu this study, we investigated the individual exposure levels of cat allergen, Fel d1, among asthmatic schoolchildren sensitized to cats. We studied the exposure relationship with symptoms, medication, lung functions, bronchial hyperreactivity (BHR) and mediators of allergic inflallrmation.
Methods: Ten school children with known allergy to cats were selected from 5 schools in Linköping, Sweden. All children had positive skin test to cats. We collected dust samples from homes and schools. All children carried a portable air-sampler in the schools during the period of 4-6 weeks. Air was also sampled fi·om the bedroom. The children performed lung function (PEF) twice daily using a digital Peak flow meter. They maintain symptom and medication chart once in a week. We performed methacholine bronchial provocation test (PD20) and analyzed mediators of allergic inflammation (s-ECP, EPX and MPO) iu blood and urine at the beginning and at the end of the study period. Dust and air samples were analyzed for major cat allergen (Fel d1) using ELISA.
Results: Exposure levels of cat allergen varied from 0,5 µg/g to 751 µg/g dust in homes (median, 36 µg/g) and from 17 µg/g to 378 µg/g in schools (median, 137 µg/g). Airborne allergen levels varied from 13 to 2184 pg/m3 (median, 43 pg/m3) in the homes and 68 to 7718 pg/m3 (median 352 pg/m3) in the schools. The mediators of allergic inflammation ranged from 4 to 57 µg/L for ECP, from 12 to 73 µg/L for EPX and from 148 to 581 µg/L for MPO. All children had bronchial hyperreactivity and all but one child used asthma/allergy medicine during the entire study period. A significant relationship (p<0.05) was found between the peak allergen exposure and symptoms, airborne allergens and BHR of the children.
Conclusions: Our study suggests, that school is an important source of cat allergen exposure, that cat sensitized asthmatic children inhale a substantial amount of cat allergen in the schools, that despite treatment of asthma including regular use of inhaled corticosteroids, 8 pg to 2336 pg of cat allergen inhaled per minute is sufficient enough to maintain a continuous airway hyper-responsiveness among this group of children.