OBJECTIVE: To determine the effect of climatic factors on immune markers in children with Dermatophagoides farinae induced asthma. METHODS: Serum concentrations of macrophage migration inhibitory factor (MIF), eosinophil cationic protein (ECP) and D. farinae-specific immunoglobulin E (DF-sIgE), together with peripheral blood eosinophil counts, were measured in children with D. farinae induced (n Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 75) or non-D. farinae-induced asthma (n Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 17), and in healthy controls (n Euro Surveillance (Bulletin Europeen Sur Les Maladies Transmissibles; European Communicable Disease Bulletin) 30). Mean temperature and relative humidity in the month before enrolment were calculated from meteorological data. RESULTS: MIF, ECP and eosinophil counts were significantly higher in children with D. farinae-induced asthma than in controls, but comparable with non-D. farinae-induced asthma. Children with D. farinae-induced asthma in a low temperature (< 16 degrees C) or low relative humidity (< 70%) climate had significantly lower DF-sIgE, MIF, ECP and eosinophil counts than those in a high temperature or high humidity climate. DF-sIgE correlated positively with MIF, ECP and eosinophil count in D. farinae-induced asthma. CONCLUSIONS: Temperature and humidity influenced MIF, ECP, eosinophil count and DF-sIgE in D. farinae-induced asthma. Understanding this relationship may provide new strategies for asthma prevention and treatment.