Introduction
Allergy, one of the most common types of hypersensitivity diseases, typically includes asthma, hay fever, atopic eczema and food allergies and may cause symptoms such as eye redness, sneezing, runny nose and even death. In recent decades, the incidence of allergic diseases has increased annually worldwide 1-3. For example, the estimated rates of food allergies increased from 3.5% to 6% in the United Sates 4. The prevalence of asthma in American adults increased from 7.21% in 2000 to 8.52% in 2009, and one study speculated an increase in the number of patients aged older than 14 years with asthma in mainland China 5. In addition to affecting the quality of life, a significant economic burden of these diseases was transferred to society and the national health care system4. Allergy is caused by exaggerated immune sensitivity to certain environmental substances (called allergens), which are usually food, plants, animals, insects and so on. Therefore, the study of the prevalence of sensitization to allergens is key for preventing and treating allergic diseases.
Many studies have focused on the prevalence of allergens and found an increase in the prevalence of allergies. The increase was found to be associated with economic improvement, lifestyle, climate change, and geographical and seasonal variations 6, 7. China is a large country with a rapidly developing economy, wide geography, and a diverse climate and diverse lifestyles. Although a series of studies have explored the prevalence of allergen sensitization in China, the majority of them focus on one part of geography in China8, 9. In 2009, a study was conducted to estimate the prevalence of 13 common aeroallergens among patients with allergic asthma and/or rhinitis in mainland China 6. Although the study investigated the differences in the prevalence and pattern of allergen sensitizations in four regions of China, it only paid attention to aeroallergens and did not consider food allergens. In this study, the skin prick test (SPT) was used to detect the sensitization to allergens. The method has low accuracy for positive results because it is heavily affected by certain factors, such as the skill of the tester, reagent used, interpretation of results and so on 10. Furthermore, dividing China into only four regions may neglect detailed information about the characteristics of sensitization prevalence in different places in China. Therefore, our research has the following different characteristics compared with previous studies: 1) covering a variety of allergic diseases, 2) exploring both aeroallergens and food allergens simultaneously, 3) including a large set of data from seven regions of mainland China, and 4) using an internationally recognized method of sIgE testing, ImmunoCAP, to detect sensitization. The above advantages may help us obtain more accurate and reliable results and conclusions.
In this paper, we explored the prevalence and patterns of sensitization to the four most common food allergens and five aeroallergens among patients with allergic symptoms in all the seven geographic regions of mainland China. The influences of seasonal and age variations on prevalence were also investigated. Furthermore, we specifically explored the factors that influenced these variations. Allergen sensitization patterns in different population demographics may contribute to improving the diagnosis and prevention of allergic diseases and then reducing economic losses.