Allergic diseases in India - Prevalence, risk factors and current challenges.

Epidemiological studies have shown a rise in the prevalence of allergic diseases in India during the last two decades. However, recent evidence from the Global Asthma Network study has observed a decrease in allergic rhinitis, asthma and atopic dermatitis in children. Still, with a population over 1.3 billion, there is a huge burden of allergic rhinitis, asthma and atopic dermatitis, and this is compounded by an unmet demand for trained allergy specialists and poor health service framework. There is wide variation in the prevalence of allergic diseases between different geographical locations in India, and the reasons are unclear at present. This may at least in part be attributable to considerable heterogeneity in aero-biology, weather, air pollution levels, cultural and religious factors, diet, socioeconomic strata and literacy. At present, factors enhancing risks and those protecting from development of atopy and allergic diseases have not been well delineated, although there is some evidence for the influence of genetic factors alongside cultural and environmental variables such as diet, exposure to tobacco smoke and air pollution and residence in urban areas. This narrative review provides an overview of data from India regarding epidemiology, risk factors and genetics and highlights gaps in evidence as well as areas for future research.

Pediatric allergic diseases in the Indian subcontinent-Epidemiology, risk factors and current challenges.

INTRODUCTION: India is low-middle-income country (LMIC) with a population of 1.3bn, comprising about 20% of the global population. While the high-income Western countries faced an "allergy epidemic" during the last three decades, there has been a gradual rise in prevalence of allergic diseases in India. METHODS: Narrative review. RESULTS AND DISCUSSION: Allergic diseases occur as a consequence of a complex interplay between genetic and environmental factors. There are multiple contrasting determinants that are important to consider in India including high levels of air pollution, in particular PM2.5 due to burning of fossil fuels and biomass fuels, diverse aero-biology, tropical climate, cultural and social diversity, religious beliefs/myths, linguistic diversity, literacy level, breastfeeding and weaning, diet (large proportion vegetarian), and high incidence rates of TB, HIV, malaria, filariasis, parasitic infestations, and others, that not only shape the immune system early in life, but also impact on biomarkers relevant to allergic diseases. India has a relatively weak and heterogeneous healthcare framework, and allergology has not yet been recognized as an independent specialty. There are very few post-graduate training programs, and allergic diseases are managed by primary care physicians, organ-based specialists, and general pediatricians. Adrenaline auto-injectors are not available, there is patient unaffordability for inhalers, nasal sprays, and biologics, and this is compounded by poor compliance leading to 40%-50% of asthmatic children having uncontrolled disease and high rates of oral corticosteroid use. Standardized allergen extracts are not available for skin tests and desensitization. This article provides a critical analysis of pediatric allergic diseases in India.

Effect of area of residence on patterns of aeroallergen sensitization in atopic patients.

BACKGROUND: An association with sensitization to inhaled allergens and allergic rhinitis and asthma has been established. A recent study concluded that the disparity in allergen sensitization might primarily be caused by environmental factors rather than genetic differences. The primary objective was to identify potential differences in sensitization among subjects with the same ethnicity in South India who reside in different environments. METHODS: Five hundred forty-six patients presenting to a tertiary allergy center with allergic rhinitis and or asthma underwent evaluation using a structured questionnaire, skin-prick testing to common aeroallergens, and spirometry and were categorized according to area of residence. RESULTS: The most common allergens causing sensitization were house-dust mite (range, 65-70%), trees (range, 52-56%), and cockroaches (range, 39-53%). There was lower risk of sensitization to cockroach allergens for subjects <21 years old living in suburban (odds ratio [OR], 0.32; 95% confidence interval [CI], 0.12-0.81) and rural environments (OR, 0.33; 95% CI, 0.11-0.96) compared with subjects <21 years old living in urban areas. There was higher risk of sensitization to fungi in subjects <21 years old living in suburban areas (OR, 1.51; 95% CI, 0.60-3.77) and rural environments (OR, 2.71; 95% CI, 0.98-7.48) compared with subjects <21 years old living in urban environments. CONCLUSION: Sensitization patterns are similar in different areas of residence except in younger subjects. Sensitization to fungi was higher in younger subjects from the rural area and cockroach sensitization were higher in younger subjects from urban areas. Sensitization is an important precursor of clinical allergic disease and further studies to unravel the complex gene-environment interactions of aeroallergen sensitization in different environments are needed.

Effect of animal contact and microbial exposures on the prevalence of atopy and asthma in urban vs rural children in India.

BACKGROUND: Environmental factors, including microbial exposures and close animal contact, are implicated in the lower prevalence of asthma and allergy in rural vs urban children. OBJECTIVES: To determine (1) the prevalence of asthma, rhinitis, eczema, and atopic sensitization in rural and urban children in India; (2) differences in microbial and animal exposures in these locales; and (3) whether differences in environmental exposures account for the different rates of asthma and atopy in these locales. METHODS: One child from each of 50 urban (Mysore) and 50 rural (Vinobha) households in southern India was randomly selected for data analysis. Allergy, asthma, health, environment, and lifestyle information was obtained using a questionnaire and household inspections. Atopy was determined via skin prick testing for common allergens. Endotoxin content was measured in house dust samples. RESULTS: Children from rural vs urban areas had lower prevalences of self-reported asthma (8% vs 30%; P = .005), rhinitis (22% vs 42%; P = .03), and atopic sensitization (36% vs 58%; P = .03). Higher median dust endotoxin loads were found in rural vs urban households (6.50 x 10(4) EU/m2 vs 1.27 x 10(4) EU/m2; P < .001). In multivariate analysis, close indoor animal contact (adjusted odds ratio [OR] 0.2; 90% confidence interval [CI], 0.05-0.9), outdoor animal contact (OR, 0.3; 90% CI, 0.1-0.8), and exclusive breastfeeding for at least 6 months (OR, 0.2; 90% CI, 0.1-0.5) were associated with lower atopic sensitization; mud flooring was associated with lower self-reported wheezing (OR, 0.1; 90% CI, 0.02-1.0). CONCLUSION: Children in India who live with close animal contact and mud flooring and who were exclusively breastfed in infancy are less likely to develop asthma, rhinitis, and atopic sensitization.