BACKGROUND. Asthma and allergic rhinitis affect 15% and 38% of South African (SA) children, respectively. The housedust mite (HDM) is
the most significant indoor aeroallergen. Typical HDM species include Dermatophagoides pteronyssinus, D. farinae and Blomia tropicalis.
Conventional skin-prick testing (SPT) panels only test for Dermatophagoides. B. tropicalis has been described in the tropical and subtropical
regions, but is not routinely tested for in SA.
OBJECTIVE. To ascertain the significance of B. tropicalis as an aeroallergen in northern coastal KwaZulu-Natal Province (KZN), a tropical
environment, and in Johannesburg in the highveld, where the climate is milder and less humid.
METHODS. Children aged 1 - 18 years with features of allergic rhinitis and/or asthma were recruited over a 6-month period from Alberlito
Hospital in northern KZN and the Clinton Clinic in Johannesburg. SPTs included Dermatophagoides and B. tropicalis. Sensitisation was
defined as a wheal 3 mm greater than the negative control.
RESULTS. Eighty-five subjects were included, 50 in northern KZN and 35 in the Johannesburg arm; 52% of subjects in northern KZN and
3% in Johannesburg were sensitised to B. tropicalis, with a significant difference between these centres (p<0.05). Of the 52% sensitised to
B. tropicalis in northern KZN, half were sensitised only to B. tropicalis.
CONCLUSION. There is a high prevalence of B. tropicalis allergy in the tropical northern KZN region and a much lower prevalence in the
Johannesburg region. Routine testing for B. tropicalis allergy should be employed in northern KZN.