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Background: Environmental exposures are involved in the pathogenesis of the allergic phenotype and in determining which individual triggers a person becomes sensitized to. Atopic dermatitis (AD) may modulate these effects through increased penetration through the skin modifying the immune system and AD may be triggered or intensified by environmental exposures. These exposures and immune‐modulating factors may differ in urban and rural environments. Objectives: To compare house dust composition in urban and rural settings and correlate them with AD outcomes. Methods: Dust samples were collected from the beds of 156 children aged 6 months to 3 years. 42% of participants had atopic dermatitis. Samples were analyzed for bacterial endotoxin, fungal (β‐1,3‐glucan) levels, and house dust mite, cockroach, dog, cat, mouse, and peanut allergen. Exposures were compared in urban and rural environments and in participants with and without AD. Results: Endotoxin but not fungal β‐glucan exposure is higher in the environment of healthy controls than children with AD in both urban and rural settings. House dust mite allergen exposure is high in urban and rural settings with Dermatophagoides detected in 100% of samples. Cat and dog allergen exposure mirrors pet ownership patterns which differ slightly between groups and environments. Mouse allergen exposure is higher in urban homes. Conclusion: Environmental endotoxin may be protective against AD in both urban and rural settings. There are marked differences in allergen exposure in urban and rural settings, but these are unlikely to be important protective or risk factors. [ABSTRACT FROM AUTHOR]

Background: Previous studies have shown that a child's risk of developing atopic disease is impacted by both genetic and environmental factors. Because small children spend the majority of their time in their homes, exposure to microbial factors in their home environment may be protective or risk factors for development of atopic diseases, such as atopic dermatitis. Methods: Dust samples from the homes of 86 Black South African children 12 to 36 months old were collected for analysis of the bacterial microbiome. This case‐control study design included children with and without atopic dermatitis from rural and urban environments. Results: Significant differences in bacterial composition and diversity were found when comparing children with and without atopic dermatitis. Furthermore, house dust microbiota was significantly different in rural and urban areas. Differences were best accounted for by higher relative abundance of Ruminococcaceae, Lachnospiraceae, and Bacteroidaceae families in rural compared with urban houses. Levels of Ruminococcaceae were also found to be significantly depleted in the house dust of rural children with atopic dermatitis as compared to control children. Conclusions: House dust composition may be an important risk factor for the development of atopic disease, and this association may be driven in part by the gut microbiome. Low levels of the Ruminococcaceae family from Clostridia class in particular may explain the association between urban living and atopy. However, further research is needed to elucidate these links. [ABSTRACT FROM AUTHOR]

Background: Allergens can act as disease‐triggering factors in atopic dermatitis (AD) patients. The aim of the study was to elucidate the molecular IgE sensitization profile in children with and without AD living in urban and rural areas of South Africa. Methods: Specific IgE reactivity was assessed in 166 Black South African children aged 9‐38 months using a comprehensive panel of microarrayed allergens. According to clinical characterization children fell in four groups, urban AD cases (n = 32), urban controls (non‐AD, n = 40), rural cases (n = 49) and rural controls (non‐AD, n = 45). Results: IgE reactivity to at least one of the allergens was detected in 94% of urban and 86% of rural AD children. House dust mite (HDM; 81% urban, 74% rural AD) and animal‐derived allergens (50% urban, 31% rural AD) were the most frequently recognized respiratory allergens, whereas IgE to pollen allergens was almost absent. Urban AD children showed significantly higher frequency of IgE reactivity (50%) to mouse lipocalin, Mus m 1, than rural AD children (12%). The most frequently recognized food allergens were from egg (63% urban, 43% rural AD), peanut (31% vs 41%), and soybean (22% vs 27%), whereas milk sensitization was rare. α‐gal‐specific IgE almost exclusively occurred in rural children (AD: 14%, non‐AD: 49%). Conclusion: Molecular allergy diagnosis detects frequent IgE sensitization to HDM, animal but not pollen allergens and to egg, peanut, and soy, but not milk allergens in African AD children. Urban AD children reacted more often to Mus m 1, whereas α‐gal sensitization is more common in rural children likely due to parasite exposure. [ABSTRACT FROM AUTHOR]

This study describes and compares allergic diseases and sensitization in urban and rural children in the SAFFA study cohort as well as infant feeding patterns and nutritional status. We assessed the relationship between nutritional status, breastfeeding, complementary feeding patterns, and atopic diseases including aeroallergen and food allergen sensitization, self‐reported atopic dermatitis, allergic rhinitis, asthma, and challenge‐proven food allergy (FA). Methodology: A total of 1185 urban and 398 rural toddlers aged 12‐36 months were screened for food sensitization (FS) and FA using skin prick testing and oral food challenges. Of these, 535 and 347, respectively, were additionally screened for aeroallergen sensitization. Information was collected on infant feeding practices, and anthropometric measurements and clinical signs for atopy were documented. Results: Markedly higher rates of allergy (asthma 9.0% vs 1.0%, eczema 25.6% vs 2.0%, rhinitis 25.3% vs 3.3%, and FA 2.5% vs 0.5%) exist in urban vs rural children. 13.1% unselected urban South African children were sensitized to aeroallergens compared to 3.8% of their rural counterparts and 9.0% to any food compared to 0.5%. Exclusive breastfeeding duration was longer, and there was a later introduction of allergenic foods in rural communities. Obesity rates were similar between the two groups, but rural children were more likely to be stunted. Being overweight was associated with asthma in urban but not rural settings. In the urban cohort, children with FS and allergy were thinner than their peers. Conclusion: Allergy and sensitization rates are significantly higher in unselected urban South African toddlers than their rural counterparts. Risk and protective factors for allergy and atopy may differ between urban and rural settings. [ABSTRACT FROM AUTHOR]

Background: Severe meat allergy with anaphylaxis may be caused by sensitization to alpha‐gal. Levels of alpha‐gal sensitization that correlate with high risk of meat allergy are currently unknown. We have identified an area with a high prevalence of reported red meat allergy which offered the opportunity to evaluate the diagnostic value of IgE antibody tests. Methods: To determine levels of alpha‐gal IgE and alpha‐gal:total IgE ratio in a large cohort of subjects with challenge‐proven meat allergy compared with control subjects from the same environment, we conducted fieldwork assessing 131 participants who reported adverse reactions to meat, and 26 control subjects, by questionnaires, IgE sensitization to alpha‐gal and oral food challenge to beef sausage. Results: Eighty‐four participants were diagnosed with alpha‐gal allergy. Alpha‐gal IgE ranged between 0.7 and 344.5 kU/L. Alpha‐gal:total IgE ratio ranged from 0.1% to 67.6%. Logistic regression analysis showed both alpha‐gal IgE and alpha‐gal:total IgE ratio strongly correlated with meat allergy, with AUC of 0.95. The values giving the best correct classification were IgE of 2.00 kU/L and ratio of 0.75%. The value above which there is a 95% probability of meat allergy is IgE>5.5 kU/L and ratio of 2.12%. Conclusion: Alpha‐gal allergy in a population with a high prevalence of reported red meat allergy showed a more rapid onset of symptoms than previously described and a high prevalence of isolated subjective gastrointestinal manifestations. Cutoff values are described for levels of sensitization to alpha‐gal IgE and alpha‐gal:total IgE ratio that are highly likely to result in clinically significant meat allergy. [ABSTRACT FROM AUTHOR]