Prevalence of allergy, patterns of allergic sensitization and allergy risk factors in rural and urban children

BACKGROUND: We aimed to compare the prevalence of allergic diseases and sensitization in children living in urban and rural areas and to identify potential risk/protection factors associated with allergy. METHODS: School children 12-16 years old, from urban community (n = 201) and rural area (n = 203) were recruited. The data obtained by questionnaire were referred to doctors' diagnosis, skin prick tests (SPTs), and serum specific and total IgE assessment. RESULTS: The prevalence of allergic diseases in urban children was significantly higher as compared with rural children [asthma 16.42%vs 1.97% (P < 0.001) allergic rhinitis 38.81%vs 10.84% (P < 0.001)]. Positive SPTs to at least one allergen was found in 63.7% of urban and 22.7% rural children (P < 0.001). Significantly higher percentage of allergic rural than urban children were monosensitized or sensitized to 2-4 allergens, but almost a fourfold higher percentage of allergic urban children was found to be sensitized to five or more allergens (P < 0.0001). The history of frequent upper respiratory factor (URT) infections, antibiotic therapy, tonsiltectomy/adenoidectomy were positively associated with development of atopy and sensitization. CONCLUSION: Our findings confirm that residence of rural area is associated with a significant lower prevalence of allergic sensitization and symptoms in school children. Several risk and protective factors related to environment and style of life could be identified in both environments.     

Lead exposure in urban and rural school children in Ghana

Human exposure to lead in non industrial urban areas is commonly ascribed to vehicular combustion of leaded gasoline. This belief is based on results of studies in societies with high vehicular density which show emission of lead fumes into the air by automobiles that use gasoline with high lead content. To assess this view, blood lead levels were evaluated in 11 to 15-year old school children in urban and rural communities of the Greater Accra Region, Ghana. Blood lead levels was significantly higher in all the urban children studied (mean +/-SD: 8.3+/- 12.7g/dl) than in their rural counterparts (4.0+/-7.2g/dl) (P<0.002). The trend was the same when only those who tested positive for blood lead were considered (24.1+/- 9.2g/dl, urban compared with 14.6+/- 5.8g/dl, rural). The prevalence of lead exposure was, however, not significantly different between the two groups (34.3. percent, urban and 27.1 per cent, rural). The presence of anaemia and/or increased urine total protein levels was unrelated to the blood lead levels in the children form both communities. Although a set goal to achieve lead free gasoline is desirable, the closeness of the prevalence rate of lead exposure obtained in the study indicate that factors other than leaded gasoline may be important determinant in exposure to lead in the Ghanaian community.     

Differences in sensitization rates to outdoor aeroallergens, especially citrus red mite (Panonychus citri), between urban and rural children.

BACKGROUND: A recent investigation has suggested that citrus red mite (Panonychus citri, CRM) is the most important allergen in citrus-cultivating farmers with asthma and allergic rhinitis. OBJECTIVE: A cross-sectional survey was performed to evaluate the prevalence of asthma and chronic rhinitis symptoms and sensitization to common indoor and outdoor aeroallergens, including CRM and Japanese cedar pollen, in rural and urban Korean children. METHODS: A total of 2,055 children (1,055 subjects living in rural areas with citrus farms and 1,000 controls in urban areas without citrus farms) were enrolled. They were evaluated by a questionnaire, and by skin prick tests with 13 common indoor and outdoor aeroallergens, including CRM and Japanese cedar pollen. RESULTS: The prevalence of wheezing and chronic rhinitis symptoms during the last 12 months was 8.3% and 35.7% in the rural children and 10.5% and 22.4% in the control group. The most common sensitizing allergens in order of decreasing frequency were Dermatophagoides pteronyssinus (26.6%), Dermatoplagoides farinae (22.7%), CRM (14.2%), cockroach (11.3%), and Japanese cedar pollen (9.7%) among the rural children, but the sensitization rates to CRM and Japanese cedar pollen were 1.3% and 0.2% among the control children, respectively. The prevalence of wheeze during the last 12 months was not different between rural children with sensitization to CRM or Japanese cedar pollen and those without sensitization (5.4% vs 6.1%; 6.9% vs 5.9%). However, the prevalence of chronic rhinitis during the last 12 months was higher among those with sensitization to CRM or to Japanese cedar pollen than among those without sensitization (40.8% vs 34.4%; 51.5% vs 33.5%). CONCLUSIONS: CRM is a common sensitizing allergen in rural children, and the sensitization rates to outdoor aeroallergens, especially CRM and Japanese cedar pollen, are very different between children from rural and urban areas in Korea.     

The prevalence of allergic diseases in primary school children in Edirne, Turkey

Background Allergic diseases present a major health burden for children as shown by the rising morbidity and increased mortality from asthma. Information on the prevalences of allergic disorders and contributing factors as well will help to establish feasible measures to change this trend, and more efficient assignment of the limited health resources. Objective To assess the prevalences of asthma and other allergic diseases and the contribution of various risk factors in primary school children in Edirne, Turkey. Methods Children aged 7 to 12 in primary schools in the municipality and 24 villages of Edirne were surveyed via a questionnaire completed by the parents. The cumulative (lifetime) and current (last 12 months) prevalences of allergic diseases and the presence of passive smoking, atopic family history, animal contact and breast-feeding in infancy were determined. Results A total of 5412 children (70.1% from the metropolitan and 29.9% from the rural area) were enrolled. The cumulative and current prevalences of all allergic diseases were 24.6% and 9.9% respectively. The cumulative (lifetime) prevalences of bronchial asthma, wheezing, allergic rhinitis and atopic dermatitis were 16.4%, 18.9%, 12.3% and 2.2%, and the current (last 12 months) prevalences were 5.6%, 5.8%, 4.5% and 0.9% respectively. Three-fourths of the children were exposed to tobacco smoke at home. Atopic heredity appeared the most prominent risk factor for any allergic disorder. Neither age, breast-feeding nor place of habitation affected the occurrence of allergic disorders. Animal contact was a significant risk factor for asthma and wheezing (adjusted odd ratios (OR) and 95% confidence intervals (CI) for current prevalences are 1.38 (CI= 1.04–1.83) and 1.35 (CI= 1.02–1.78) respectively), exposure to indoor tobacco smoke for wheezing (OR =1.52, CI= 1.10–2.09), and male gender for asthma (OR = 1.50, CI= 1.16–1.93). Current prevalences for all allergic diseases were significantly lower than those previously reported in Ankara, Turkey. Conclusions Allergic diseases are a major health burden for primary school children in Edirne, Turkey. Although atopic heredity appears to be the foremost important risk factor, reduction of exposure to indoor tobacco smoke and animal contact, especially for those with atopic family history, are important preventive measures. The impact of environmental exposures on distinguishing prevalences of allergic diseases in Ankara and Edirne should be further investigated.     

The relationship between exhaled nitric oxide and allergic sensitization in a random sample of school children

BACKGROUND: Exhaled nitric oxide (NO) has been proposed as novel a non-invasive marker of airway inflammation. OBJECTIVE: The level of exhaled NO was determined in a random sample of school children (7-12 years old) with the aim of investigating the relationship between exhaled NO and sensitization to common allergens. RESULTS: In the 450 children tested by skin prick tests (SPT), the prevalence of sensitization was 29.5% (overall), 21.9% (sensitization to indoor allergens), and 15.0% (sensitization to outdoor allergens). Regression analysis showed that levels of exhaled nitric oxide were closely associated with various measures of sensitization to aeroallergens. Sensitization to indoor allergens was associated with higher levels of exhaled NO (eNO) than sensitization to outdoor allergens when assessed by IgE but not when assessed by SPT. Children with reported wheeze in the past 12 months had much stronger associations between sensitization and eNO than children without wheeze. CONCLUSION: We conclude that allergic sensitization is strongly associated with increased levels of exhaled NO, especially in children with wheeze.     

Influence of skin prick test criteria on estimation of prevalence and incidence of allergic sensitization in children

In a prospective cohort study on atopy in childhood, three skin prick tests (SPT) were performed in 1135 primary schoolchildren over a 2–year period. We studied the development of average sizes of allergen wheals in reactive children and of average sizes of histamine wheals in all children, and we investigated the influence of choice of SPT criterion on the prevalence and incidence of sensitization. A year-to-year increase of average allergen wheal sizes as well as of average histamine wheal sizes was observed. These increases seemed to be related to the natural growth of the children. Furthermore, an observer bias effect of the person who did the pricking on average wheal sizes was found. There were considerable differences in estimations of prevalences and incidences depending on the definition of SPT criterion. Estimations using a criterion based solely on the allergen wheal size were affected by variation of allergen wheal sizes caused by growth and observer effects. The ratio criterion was not influenced by observer effects, nor did it seem to be affected by aging effects. In conclusion, our data suggest that the ratio criterion, which relates the size of the allergen wheal to the size of the histamine wheal, is the most appropriate SPT criterion because it is not affected by growth of allergen wheals in childhood and it appears to compensate for possible observer bias.     

Growth of urban school children in Malawi.

The objective of this cross-sectional study was to assess growth pattern of urban school children in Malawi from low socio-economic strata and to compare anthropometric measurements of the children to data from the region of South-Central Africa and to international standards. A total of 493 urban school children aged 6-17 years were selected randomly from two primary schools in semi-urban Blantyre, the largest city in Malawi. Anthropometric measurements included height, weight, mid-upper arm circumference, triceps skinfold thickness, mid-upper arm muscle circumference and maximal grip strength of the stronger hand. All parameters of Malawian children of both sexes were lower than medians of WHO/NCHS reference data. Expressed as percentage of WHO/NCHS references, the relative means of height, weight, mid-upper arm circumference and mid-upper arm muscle circumference of Malawian girls were considerably higher than those of boys, and older girls had better parameters than younger ones. Older pupils of both sexes had higher triceps skinfold thickness relative to the international references than the younger children. Mean maximal grip strength values of boys and girls were not significantly different. For girls, the relative values increased with age, while for boys they decreased. It is concluded that younger primary school pupils have similar body sizes to their counterparts from the region. Adolescents, particularly girls, have more favourable anthropometric parameters which approach WHO/NCHS reference data.     

Dietary antioxidant intake, allergic sensitization and allergic diseases in young children

Background:  Allergic diseases have risen in prevalence over recent decades. The aetiology remains unclear but is likely to be a result of changing lifestyle and/or environment. A reduction in antioxidant intake, consequent to reduced intake of fresh fruits and vegetables, has been suggested as a possible cause.
Objective:  To investigate whether dietary antioxidant intake at age 5 was related to atopy at 5 and 8 years of age amongst children in an unselected birth cohort.
Methods:  Children were followed from birth. Parents completed a validated respiratory questionnaire and children were  skin prick tested at 5 and 8 years of age. Serum IgE levels were measured at age 5. At age 5, antioxidant intake was assessed using a semi-quantitative food frequency questionnaire (FFQ). A nutrient analysis program computed nutrient intake, and frequency counts of foods high in the antioxidant vitamins A, C and E were assessed.
Results:  Eight hundred and sixty-one children completed both the respiratory and FFQ. Beta-carotene intake was associated with reduced risk of allergic sensitization at age 5 [0.80 (0.68–0.93)] and 8 [0.81 (0.70–0.94)]. In addition, beta-carotene intake was negatively associated with total IgE levels ( P  = 0.002). Vitamin E intake was associated with an increased risk of allergic sensitization [1.19 (1.02–1.39)], only at age 5. There was no association between antioxidant intakes and wheeze or eczema.
Conclusion:  Increased beta-carotene intake was associated with a reduced risk of allergic sensitization and lower IgE levels, in  5- and 8-year-old children. Dietary antioxidants may play a role in the development of allergic sensitization.     

Allergic disease and sensitization in Steiner school children

BACKGROUND: The anthroposophic lifestyle has several features of interest in relation to allergy: for example, a restrictive use of antibiotics and certain vaccinations. In a previous Swedish study, Steiner school children (who often have an anthroposophic lifestyle) showed a reduced risk of atopy, but specific protective factors could not be identified. OBJECTIVE: To investigate factors that may contribute to the lower risk of allergy among Steiner school children. METHODS: Cross-sectional multicenter study including 6630 children age 5 to 13 years (4606 from Steiner schools and 2024 from reference schools) in 5 European countries. RESULTS: The prevalence of several studied outcomes was lower in Steiner school children than in the reference group. Overall, there were statistically significant reduced risks for rhinoconjunctivitis, atopic eczema, and atopic sensitization (allergen-specific IgE > or =0.35 kU/L), with some heterogeneity between the countries. Focusing on doctor-diagnosed disease, use of antibiotics during first year of life was associated with increased risks of rhinoconjunctivitis (odds ratio [OR], 1.97; 95% CI, 1.26-3.08), asthma (OR, 2.79; 95% CI, 2.03-3.83), and atopic eczema (OR, 1.63; 95% CI, 1.22-2.17). Early use of antipyretics was related to an increased risk of asthma (OR, 1.54; 95% CI, 1.11-2.13) and atopic eczema (OR, 1.32; 95% CI, 1.02-1.71). Children having received measles, mumps, and rubella vaccination showed an increased risk of rhinoconjunctivitis, whereas measles infection was associated with a lower risk of IgE-mediated eczema. CONCLUSION: Certain features of the anthroposophic lifestyle, such as restrictive use of antibiotics and antipyretics, are associated with a reduced risk of allergic disease in children.     

Smoking exposure and allergic sensitization in children according to maternal allergies.

BACKGROUND: Although the negative impact of environmental tobacco smoke (ETS) on airway diseases in children is well known, the effect of ETS on allergic sensitization is still debated. OBJECTIVE: To evaluate how maternal allergies modulate the effect of tobacco exposure on allergic sensitization in childhood. METHODS: Of 9000 children in grades 4 and 5 selected in 6 cities in France, 7798 participated in a survey that consisted of an epidemiologic questionnaire, skin prick testing to common allergens, and skin examination for eczema. Tobacco exposure was obtained from parent questionnaires. RESULTS: Twenty-five percent of the children had allergic sensitization, 25.2% had eczema, 11.6% had allergic rhinitis, 9.9% had asthma, and 8.3% had exercise-induced asthma. Twenty percent of the children were exposed to tobacco in utero. Maternal exposure had a greater impact than paternal exposure on children's allergic sensitization. Prenatal exposure was more associated with sensitization than postnatal exposure. Children with maternal allergies and exposure to maternal ETS during pregnancy were at higher risk for sensitization to house dust mite (25.7% vs. 14.0%; odds ratio, 1.95; 95% confidence interval, 1.19-3.18; P = .006). In contrast, sensitization to food allergens was not associated with tobacco exposure. CONCLUSIONS: Children exposed to maternal smoking had a higher risk of sensitization to house dust mite, especially when the mothers were allergic.     

Traffic exposure and allergic sensitization against latex in children

BACKGROUND: Latex antigens have been found in urban air samples and in debris deposited near freeways. OBJECTIVE: We investigated whether exposure to road traffic in a large city is associated with allergic sensitization against latex in children. METHODS: A population-based sample of 2505 children aged 5 to 11 years was examined in a cross-sectional study in the city of Dresden, Germany. Specific IgE levels against latex and a panel of common aeroallergens (timothy grass, rye, birch, mugwort, Cladosporium herbarum, Dermatophagoides pteronyssinus, cat dander, and dog dander) was determined by using a fluorescence immunoassay (CAP Pharmacia). Traffic exposure was assessed by (1) parental self-report on traffic frequency and truck traffic in the street of residence, (2) traffic counts, and (3) measurements of benzene at 182 points on a 1-km(2) grid for 1 year, which were used to estimate the children's individual exposure at the home address. RESULTS: Eight hundred fifty-four (34.1%) of the children were sensitized against any of the allergens, and 150 (6.0%) had specific IgE (>0.35 kU/L) against latex. The prevalence of latex sensitization was not positively associated with self-reported traffic exposure, traffic counts in the street of residence (adjusted prevalence odds ratio for >5000 vs < or =5000 cars/d, 0.7; 95% confidence interval, 0.4-1.3), or benzene exposure (adjusted prevalence odds ratio for an increase of 1 microg/m(3) air, 0.8; 95% confidence interval, 0.7-1.05). CONCLUSION: The data suggest that exposure to road traffic is not associated with allergic sensitization to latex in children.     

Prevalence of hay fever and allergic sensitization in farmer's children and their peers living in the same rural community

INTRODUCTION: Lower prevalence rates of allergic diseases in rural as compared with urban populations have been interpreted as indicating an effect of air pollution. However, little is known about other factors of the rural environment which may determine the development of atopic sensitization and related diseases. OBJECTIVE: The authors tested the hypothesis that children growing up on a farm were less likely to be sensitized to common aerollergens and to suffer from allergic diseases than children living in the same villages but in nonfarming families. MATERIALS AND METHODS: Three age groups of schoolchildren (6-7 years, 9-11 years, 13-15 years) living in three rural communities were included in the analyses. An exhaustive questionnaire was filled in by 1620 (86.0%) parents. A blood sample was provided by 404 (69.3%) of the 13-15 year olds to determine specific IgE antibodies against six common aeroallergens. RESULTS: Farming as parental occupation was reported for 307 children (19.0%). After adjustment for potential covariates such as family history of asthma and allergies, parental education, number of siblings, maternal smoking, pet ownership, indoor humidity and heating fuels, farming as parental occupation was significantly associated with lower rates of sneezing attacks during pollen season (adjusted OR 0.34, 95% CI 0.12-0.89) and atopic sensitization (adjusted OR 0.31, 95% CI 0.13-0.73) whereas the association with wheeze (adjusted OR 0.77 95% CI 0.38-1.58) and itchy skin rash (adjusted OR 0.86, 95% CI 0.49-1.50) was not statistically significant. The risk of atopic sensitization was lower in children from full-time farmers (adjusted OR 0.24, 95% CI 0.09-0.66) than from part-time farmers (adjusted OR 0.54, 95% CI 0.15-1.96). CONCLUSION: Factors directly or indirectly related to farming as parental occupation decrease the risk of children becoming atopic and developing symptoms of allergic rhinitis.     

Horse chestnut (Aesculus hippocastanum) pollen: a frequent cause of allergic sensitization in urban children

We investigated the incidence of allergic sensitization and the risk factors underlying sensitization in 214 urban children exposed to horse chestnut pollen. By means of the Phadezym RAST, we found IgE specific to horse chestnut pollen in 12.6% of the urban children, whereas it occurred in only 1.9% of control subjects recruited from a rural area. Reports of allergic symptoms in spring during the horse chestnut pollen load coincided with the presence of specific IgE in 5.1% of the urban group as against 1.4% of that recruited from the rural area. Environmental factors other than those related to urban living and higher horse chestnut pollen counts had no significant impact on allergic sensitization. Increased total IgE levels (> 100 kU/1), however, and the sensitization to pollen of other species significantly raised the odds for sensitization to chestnut pollen. They were highest in highly atopic children with sensitization to pollen, especially to that of plane trees (OR = 73.9). These results suggest the relevance of horse chestnut pollen because of the high allergic sensitization rate among urban children, and they should also be borne in mind when it comes to the planting of trees in urban areas.