Background The degree of airway hyperresponsiveness in allergic asthmatic patients may be influenced by changes in environmental exposure to inhalant allergens.
Objective This study investigates the relationship between seasonal changes in exposure to house dust mite (HDM) allergens and non-specific airway hyperresponsiveness in asthmatic patients with multiple sensitizations to inhaled allergens.
Methods In 43 asthmatic patients sensitized to several inhalant allergens, lung function (FEV1), airway hyperresponsiveness (PC20 histamine), serum total IgE, house dust mite (HDM) specific IgE and number of peripheral blood eosinophils were measured during autumn 1990 (September-November) and spring 1991 (March—May). During each season. floor dust samples were collected twice from living- and bedrooms and the concentration of the HDM allergens Der p 1 and Der p 2 determined.
Results More severe airway hyperresponsiveness (lower PC20 histamine) during autumn was only found in patients sensitized to HDM(n= 32; autumn: 2.05mg/mL, spring: 4.51mg/mL (geometric means), P <0.0 1), whereas in patients not sensitized to HDM (n= 11) similar values were observed in both seasons (3.44 and 4.52 mg/mL. respectively, P= 0.56). More severe airway hyperresponsiveness of HDM sensitized patients in autumn was significantly associated with higher Der p 1 concentrations in floor dust. Aside from airway hyperresponsiveness, seasonal changes in serum total IgE and number of peripheral blood eosinophils were seen in patients sensitized to HDM,
Conclusions In allergic asthmatic patients, airway hyperresponsiveness may increase during autumn, depending on sensitization to HDM and an increase of exposure to HDM allergen.