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This study was aimed to investigate the sensitization pattern to a range of common allergens in young Singaporean children. A cross-sectional study involving 75 children aged below 3 years was carried out. They presented between December 1995 and April 2000 with symptoms of asthma, rhinitis, eczema, or food allergy. Their levels of allergen-specific serum IgE to a panel of foods (egg white, milk, soy protein, shrimp, wheat and peanut), pet dander, dust mites and cockroaches were measured with Pharmacia CAP System radioallergosorbent test kits. Serum IgE levels greater than 0.35 kU/l represented a positive result. Four children could not be tested with the complete panel because of insufficient serum. The prevalence of sensitization was highest for cow's milk (45.9%) followed by egg white (38.7%), dust mites Dermatophagoides pteronyssinus (31.4%) and Blomia tropicalis (25.5%). Sensitization to ingested allergens was significantly more prevalent in children aged 1 year or younger than in the older children (70.4% of those below 1 year, and 50% of those aged 1-3 years; p < 0.02). Sensitization to inhaled allergens, such as dust mites, was more likely to manifest as respiratory symptoms (allergic rhinitis and asthma), while ingested allergens were associated with gastrointestinal symptoms and eczema (p < 0.001). It was concluded that infants and young children are at high risk of sensitization to common environmental substances. Allergen avoidance is therefore important even in the very young. The prevalence of sensitization to food allergens is higher compared to inhalant allergens in young children.

The study of food allergy in Singaporean children is still in its infancy. Confusion and misunderstanding is common among the public. Even so, we have found certain unique features regarding food allergy among Singaporean children. "Bird's nest" has been shown to be the most common cause of anaphylaxis requiring medical attention. This allergen has not been described before. Peanuts and tree nuts are extremely uncommon causes of anaphylaxis, unlike the West. However, the pattern of sensitization to foods in children as shown by skin prick test is similar to other Western populations. The reasons for the difference between the profile foods responsible for anaphylactic reactions in our population and those of the western population, despite the similarity in sensitization profiles, are still unclear.

"Quality of Life" is a multidimensional measure encompassing the physical, emotional and social functioning of the child. The asthma specific questionnaire contains 23 questions (items) in three areas (domains) of activity, symptoms and emotions. The objective of the present study was to validate the Paediatric Asthma Quality of Life Questionnaire "PAQLQ"(copyright 1991 McMaster University). If the questionnaire is valid, a change in the child's asthma will be accompanied by a change in the "Quality of Life" questionnaire score. The questionnaire was administered twice over four weeks and the child's asthma status was assessed concurrently. Two groups were thus identified; Group A = unchanged asthma, Group B = changed asthma. Forty-seven children, aged 7 to 14 years, completed the study. Reliability of the questionnaire shows an intraclass-correlation coefficient of only 0.71. Cross-sectional construct validity was demonstrated by a significant correlation between the whole questionnaire and the clinical asthma score (p<0.001) but not in the separate domains. Longitudinal construct validity was also demonstrated by the significant correlation between change in the total questionnaire score, but not separate domains, with change in the child's asthma score (p<0.05). Responsiveness was shown by a significant difference in the magnitude of the change in the questionnaire score between the two groups (p<0.001), but again not in the separate domains. It was concluded that the questionnaire was validated as a whole but not in as convincing a manner, as has been done by others, and we are therefore in a position to advise caution in its application in our population.

Blomia tropicalis (Bt) and Dermatophagoides pteronyssinus (Dp) are the predominant domestic mites species in Singapore and Taiwan. This study aims to characterize and compare the mite sensitization profiles in both countries. Skin prick tests were performed on 203 Singaporeans with Dp and Bt crude extracts. In vitro IgE and IgG4 reactivity to extracts and specific allergens (Der p 1, Der p 2 Der p 5 and Blo t 5) were determined by immunoassays. Approximately 91% of the tested Singaporeans were skin test positive for both Bt and Dp. Both populations share similar frequencies of in vitro IgE reactivity to all the allergens tested, but they differ in the pattern and magnitude of allergen sensitization. Although Der p 1, Der p 2 and Blo t5 are major sensitizing allergens in both countries, Blo t 5 is a more potent one in Singapore, probably reflecting the high level of exposure to Bt. The unique major Bt and Dp allergens should be included for precise diagnosis and effective immuno-therapeutic treatment of mite allergy in both countries.

The genetics of asthma and atopy is complex, but can be approached by studies of both candidate genes and mapping of susceptibility loci. Genetic factors conferring susceptibility to disease may vary among ethnic groups. We present our experience with some candidate gene studies for asthma and atopy and susceptibility locus mapping for linkage to chromosome 5q.