Boys run a higher risk for atopy than girls but this gender difference is less pronounced in adulthood. The underlying mechanisms and the exact timing of this decrease in male/female ratio remain unclear. The aim of this study was to evaluate the effect of age and gender on sensitization in schoolchildren. A cross-sectional study was performed in an unbiased community population of 2021 Belgian schoolchildren, aged 3.4-14.8 yr. The overall sensitization and the sensitization for mites, mixed grass pollens and tree pollens increased significantly with increasing age. Male sex was strongly associated with sensitization (OR(adj) 2.0, 98% CI 1.6-2.4). Male predominance was more obvious in children under the age of 8 yr. After the age of 8 male predominance persisted, but a significant increase in sensitized females occurred. Our data demonstrate a significant increase in prevalence of sensitization with age and a significant decrease in male/female ratio of sensitization after the age of 8 yr, although a male predominance persists. These data are the first published data ever that document this change in male/female ratio in sensitization at this age.

Results of studies of the influence of body mass index (BMI) on the allergic status are controversial. As a part of the Aalst Allergy Study, we assessed the prevalence of the different BMI categories (underweight, normal weight, overweight, and obesity) and a possible association between BMI and atopy in 1576 unselected Belgian schoolchildren, aged from 3.4 to 14.8 yr. BMI was used to determine weight status. Skin prick testing with the most common aeroallergens was performed. A parental questionnaire documented data on respiratory and allergic disorders, demographic characteristics and other potential risk factors for sensitization. Among the total children, 4.1% of the children were underweight, 14.5% were overweight, and 7.4% were obese. More girls than boys were overweight (p = 0.015). In the group of children older than 12 yr, we found more overweight (p = 0.03) and obese (p = 0.004) girls, and more obese boys (p = 0.004) than in the younger age groups. In contrast with reports in the literature, an increased prevalence of allergic sensitization in underweight girls only [adjusted odd ratio (OR(adj)) = 2.9, 95% confidence interval (CI): 1.3-6.4] was documented. A strong association between obesity and exercise-induced respiratory symptoms was found in both boys (OR(adj) = 14.5, 95% CI: 2.9-73.3) and girls (OR(adj) = 4.9, 95% CI: 1.3-17.4). No correlations with allergic respiratory symptoms, eczema, or rhinoconjunctivitis could be documented.

Although it is generally agreed that sensitization is an important risk factor for allergic diseases, the extent to which sensitization accounts for allergic symptoms in children is controversial. As part of the Aalst Allergy Study, this cross-sectional study investigated the prevalence of allergic symptoms and their association with sensitization in an unselected population of Flemish children aged 3.4-14.8 yr. Skin prick testing with the most common aeroallergens was performed and allergic symptoms were documented by a parental questionnaire. In the children older than 6 yr, a significant association of current wheezing, current dyspnea, airway hyperreactivity, rhinoconjunctivitis, and current eczema with sensitization was found, while in the pre-school children these associations were less pronounced. The association with sensitization was strongest for rhinoconjunctivitis and current respiratory symptoms - the association was less striking for children with current eczema. The impact of a positive family history of allergy on the association with sensitization was more important for eczema than for the other analyzed allergic symptoms. Persistent and late-onset wheezers were significantly more likely than non-wheezers and transient early wheezers to be associated with sensitization and a personal history of rhinoconjunctivitis. Late-onset wheezing was associated with a positive family history of allergy, while transient early wheezing was associated with day-care attendance. An association with eczema was found for all three childhood wheezing phenotypes. The association of allergic symptoms with sensitization is significant in the older but less pronounced in pre-school children and is more pronounced for current allergic symptoms. Diagnosis and disease definition of allergy symptoms remains difficult at pre-school age. The influence of a positive family history of allergy on the association of the respective allergic symptoms with sensitization was most important for eczema. Our data confirm the atopic characteristics of the different wheeze phenotypes.

Treatment with montelukast after hospital admission for RSV bronchiolitis in children younger than 2 years of age did not reduce symptoms of cough and wheeze. We cannot exclude that a subgroup of children may, however, benefit from this treatment.

Childhood eczema is common in infants, but its nature and extent during later childhood remains unclear. In this cross-sectional study we examined the prevalence and characteristics of eczema in an unbiased community population of 2,021 Belgian schoolchildren, aged 3.4 to 14.8 years with skin prick testing and parental questionnaires. Our study identified an eczema prevalence of 23.3% and a considerable allergic comorbidity, mainly in sensitized children. The reported prevalence of eczema in infancy was 18.5% and for current eczema 11.6%. The overall sensitization rate (33.2%) as well as sensitization rates for the individual allergens were significantly higher in children with "eczema ever." Sensitization to Dermatophagoides pteronyssinus (19.6%), mixed grass pollen (15.1%), and cat (9.1%) were most common. Until the age of 6 years, boys with eczema were significantly more sensitized than girls (p = 0.007). Children with both eczema in infancy and current eczema show a tendency to be more sensitized than children with eczema in infancy only or current eczema only, but significance was only noted for a few individual allergens. Analysis of factors associated with eczema revealed a predominantly atopic profile characterized by family or personal history of allergy. Breastfeeding and environmental factors seemed to assume little relevance except for a protective effect of prematurity and having a dog at birth.