Tokelau: a unique low allergen environment at sea level.

BACKGROUND Previous studies have shown that children in Tokelau have a lower prevalence of asthma and atopy compared to Tokelauan children resident in New Zealand. We hypothesized that the low asthma and atopy prevalence in Tokelau may be associated with low indoor allergen levels. METHODS Dust was collected from bedding and floors of 76 homes and four public buildings in Tokelau and from the homes of 30 Tokelauan families in Wellington, New Zealand. Dust samples were analysed for Der p 1, Der f 1, Can f 1, Fel d 1, Bla g 2 and Blo t 5 by ELISA, and for endotoxin by a kinetic amoebocyte lysate assay. RESULTS Der p 1 levels were over 1000-fold lower in Tokelau compared to New Zealand, geometric mean levels were 0.04 and 47.0 microg/g in beds and 0.04 and 44.7 microg/g on floors, respectively. Can f 1 and Fel d 1 levels were also significantly lower in Tokelau. Bed endotoxin levels were significantly higher in Tokelau, geometric mean: 26 736 EU (endotoxin units)/g, compared to 5181 EU/g in New Zealand. Floor endotoxin levels were similar between the two countries. CONCLUSION The very low indoor allergen levels in homes in Tokelau compared to much higher levels in New Zealand homes provides a logical explanation for the lower prevalence of asthma and atopy in Tokelau, compared to New Zealand.