Allergy in China: Challenges in research, training and clinical practice

Allergic disorders have become some of the most common chronic conditions affecting people in the developed world. There is clear evidence linking economic development, urbanization and an increase in the prevalence of allergic disorders. Over the past 30 years, the pace of urbanization in China has been extraordinary and associated with rapid rise in the prevalence of allergic disorders. Notably, the urban population in China has increased from 50% in 2010 to 64% in 2020, and household income has doubled compared to 2010. The traditional Chinese diet, characterized by high vegetable consumption and relatively low consumption of animal fats, has shifted towards increased meat consumption. There has been marked improvement in hygiene across the country. All these factors probably contributed to the exponential increase in the number of patients with allergic disorders, highlighting the need for more training programmes in the field of allergy in order to cope with this growing burden. At the same time, the large number of patients presents an opportunity for research to develop preventive and treatment strategies for allergic diseases. Like in the West, the rapid urbanization in various regions in China has been linked to a significant increase in the prevalence of asthma. Similar to findings in Europe or America, rural Chinese children have a lower prevalence of asthma compared to their urban counterparts.1 Over a 15-year period, the prevalence of asthma symptoms in secondary school children has increased from 2.0% to 7.9% in the city of Guangzhou in southern China.1 The recent China Pulmonary Health Study found that 4.2% of adults in China, equivalent to 45.7 million adults, suffer from asthma.2 Alarmingly, asthma control is poor, with 15.5% of patients experiencing at least one asthma attack requiring emergency visit in the previous 12 months. Only 5.6% of the patients were receiving inhaled corticosteroid treatment. There is a need for coordinated national efforts to enhance asthma management for the millions of affected in China. Food allergies are emerging as the second wave of the allergy epidemic following asthma. However, there is a general belief that food allergy is uncommon in China when compared to Western countries. Limited access to facilities for confirming food allergies through food challenges may result in both overdiagnosis and underdiagnosis. In line with asthma, the recent EuroPrevall-INCO study revealed that the prevalence of food allergy in primary school children was highest in Hong Kong (1.5%) while it was only 0.2% in Guangzhou.3 Early-life exposures likely play a crucial role in modulating the early immune system, as evidenced by the significantly lower prevalence of food allergies in children born in mainland and migrated to Hong Kong compared to those born in Hong Kong. In China, peanut allergy is rare, while shrimp is a common trigger for food-induced anaphylaxis. The complex nature of Chinese cuisine, with its numerous ingredients and sauces, can make it challenging to pinpoint specific allergens when a reaction occurs. The lack of standardized food challenges facilities in many parts of China further complicates the accurate diagnosis of food allergies, leading to unnecessary food avoidance in many patients. Further research studies are essential to better understand the epidemiology and underlying mechanisms of food allergies in China and to develop strategies for primary prevention. Allergic rhinitis (AR) is a growing global health issue, with a rising prevalence and significant medical and socioeconomic impact. In China, the prevalence of self-reported AR has increased from 11.1% in 2005 to 17.6% in 2011.4 Similar to the high comorbidity with asthma found in Western countries, 28% of self-reported AR patients in China also report having asthma.1 The epithelial barrier hypothesis suggests that damage to the epithelial barrier caused by various toxic agents in the modern environment may contribute to the rise of allergic diseases. The rapid industrialization in China has resulted in environmental degradation, presenting significant environmental challenges. Thus, changes in living environments and lifestyles have contributed to the increased prevalence of AR in China. Identifying allergens is essential for the diagnosis and treatment of AR. Significant variation exists in topography and climate across different regions in China, leading to variations in exposure to different allergens. House dust mites (HDMs) are the primary aeroallergens in AR patients in southern China, while pollen takes precedence as the major aeroallergen in AR patients in northern China. Although our understanding of pathogenesis of AR has improved, the underlying factors driving the increase in AR in China remain to be fully elucidated. Chronic rhinosinusitis (CRS) affects 8% of Chinese adults and is a heterogeneous inflammatory disease that affects the nasal and paranasal sinus mucosa.5 Compared to Western countries, the comorbidity of AR, asthma and non-steroidal anti-inflammatory drug-exacerbated respiratory disease is relatively low among Chinese CRS patients.5 In recent years, there has been growing interest in exploring the inflammatory endotypes of CRS. Chinese CRS patients exhibit less eosinophilic and type 2 (T2) inflammation but display more pronounced neutrophilic inflammation compared to their Caucasian counterparts.5 Furthermore, Chinese CRS patients often present with a mixed inflammatory response, which may have implications for the use of T2 biologics in the Chinese population. It is noteworthy that the proportion of eosinophilic CRS has increased over the past two to three decades in China. Further research is needed to understand the underlying mechanisms driving the inflammatory response in Chinese CRS patients and to evaluate the effectiveness of treatment options, such as biologics. Allergen immunotherapy (AIT) is considered the only disease-modifying treatment for allergic conditions like AR, offering long-term clinical benefits and inducing tolerance, following a treatment course lasting 3–5 years. However, standardized allergen vaccines in China are currently limited with only a few options available for common allergens like dust mites and Artemisia pollen.6 Despite a growing number of patients with sensitivities to pet and fungal allergens, there is a lack of allergen-specific extracts for immunotherapy. There are approximately 300 million patients with AR in China, less than 1% of these individuals are treated with AIT. The current practice of AIT heavily relies on research conducted in Western countries. Clinical trials in the Chinese population are needed to assess the efficacy of AIT, particularly with sublingual immunotherapy, given the low utilization of AIT in China. Similar to other atopic disorders, there has been a substantial increase in the prevalence of atopic dermatitis (AD) in China. A recent study of AD in 12 major Chinese cities revealed a prevalence of 12.94% in children aged 1–7 years and 30.5% in infants.7 With increasing public awareness and the introduction of biologics and JAK inhibitors into clinical use for patients with moderate-to-severe AD, AD is increasing recognized to be a major health problem. However, there is still a need for better training and improved diagnosis and treatment practices among Chinese doctors, dermatologists and allergists, as misdiagnosis and under-diagnosis of AD remain common. In China, patients with skin diseases often go directly to seek care from dermatologists but not the family doctor, thus the manifestations of AD seen by Chinese dermatologists might appear to be different from those in Europe or the United States. Collaborative efforts among Chinese specialists have been focused on adapting international guidelines for AD management and conducting research to enhance knowledge of the epidemiology, pathogenesis and effective interventions.8 Extensive research studies on skin microbiome, epigenetics and epicutaneous sensitization of AD have been conducted in China contributing the understanding of the pathogenesis of AD. Further exploration into the clinical and molecular heterogeneity of AD and the underlying biological mechanisms would facilitate further breakthroughs in the field. Chronic urticaria (CU) is another common allergic skin disease in China that significantly impacts patients' daily life, presenting a considerable public health challenge. Recent data revealed that the lifetime prevalence of urticaria in China is 7.93%, with a point prevalence of 0.76%.9 Various factors, such as urban living, exposure to pollutants, anxiety, depression, thyroid disorders, Helicobacter pylori infection and a personal or family history of allergies, have been linked to a higher prevalence of CU.9 In addition, research has shown associations between CU and metabolic disorders, highlighting the importance of exploring various metabolic pathways, including proinflammatory pathway, oxidative stress and activation of the coagulation system to determine new treatment targets. While omalizumab has shown effectiveness for some patients with inadequate response to antihistamines, there are still patients with autoimmune-related CU who do not respond well to this treatment. Therefore, the development of new, safer treatment options for these patients is crucial to improving outcomes for individuals with CU. The rapidly rising prevalence of allergic disorders in China over the past few decades poses a significant public health challenge, necessitating the establishment of more training programmes to adequately address the increasing burden of allergic disease in the country. While the standard of care for allergic patients in major tertiary centres in China is on par with developed countries, there is an urgent need for more healthcare providers at the primary care and secondary care levels in the cities as well as the less developed areas across China. This work was supported by the National Key Research and Development Program of China 2023YFC2507900 and 2022YFE0131200 (Z.L.), the National Natural Science Foundation of China (NSFC) grants 82101198 and 82322018 (Y.Y.), TS Lo Foundation (GWKW), Hong Kong Research Grant Council GRF 14119320 (GWKW). The authors declare no conflicts of interest.