Introduction
Allergies are chronic immune-mediated diseases that have become a worldwide public health problem[1]. An epidemiological survey conducted by WAO revealed that 22% of total population in more than 30 countries suffer from allergic diseases[2]. In high-income countries, 20% of children have atopic dermatitis[3]. In addition, the incidence of allergic diseases has been and will continue to rise over the next two decades[4]. For individuals, allergic diseases can reduce the quality of life and productivity. A study in Canada found that 48.7% of asthmatic patients recruited experienced the drop in productivity due to asthma[5]. Allergic diseases have caused a tremendous socioeconomic burden as well. For example, researches have shown the United States has spent over $960 billion annually on asthma management[6].
COVID-19 outbreak was declared a global pandemic after the first case of Coronavirus Disease 2019 (COVID-19) was identified in Wuhan, Hubei Province, China, in 2019. During the pandemic, strict prevention and control measures have been adopted worldwide, particularly in China, among which non-pharmacological interventions (NPI), including closing public spaces, restricting gatherings, reducing unnecessary outings and maintaining social distancing wearing masks, and keeping hand hygiene. These NPIs have influenced people’s living environments and lifestyles, leading to higher indoor allergen concentrations and more time spent indoors[7].The exposure to outdoor allergens also rises as people travel more after the lifting of certain travel restrictions. These are bound to bring changes in allergen sensitization. Yet, few researches have studied the impact of COVID-19 on allergen sensitization. Understanding allergen sensitization during the pandemic can help patients identify allergens, as well as take steps to reduce allergen sensitization and allergic disease progression in a period of regular epidemic prevention and control. In this study, we analyzed the positive rates of inhaled allergen sIgE (specific antibody immunoglobulin IgE, sIgE) before and during COVID-19 to investigate its impact on allergy sensitization.