Non-pharmaceutical interventions reduced the incidence and exacerbation of allergic diseases in children during the COVID-19 pandemic.

Dear editor,

Recently, a report entitled “Incident changes of rotavirus enteritis among children during the coronavirus disease-2019 pandemic in Hangzhou, China” has aroused our strong concern[1]. Fang et al.[1] found a significant reduction in the incidence of rotavirus enteritis among children by 84.8% in the COVID-19 pandemic period in Hangzhou, China, compared to that of the last two years by the generalized linear model with the Poisson distribution. Here, we observed that changes in human lifestyle and the living environment caused by non-pharmaceutical interventions (NPIs) in COVID-19 reduced children's incidence and exacerbation of allergic diseases.

Allergic diseases, such as asthma, eczema, hay fever, and food and drug allergies, affect approximately one billion people worldwide and are the most common and economically expensive non-communicable and chronic diseases among children[2]. The International Study of Asthma and Allergies in Childhood has indicated that the environment impacts the occurrence and development of allergic diseases, and the worse the socioeconomic environment, the higher the prevalence of allergic diseases may be[3]. Allergic diseases are usually mediated by immunoglobulin E (IgE), and allergic patients are prone to produce IgE antibodies to allergy-related environmental allergens[4]. Allergen-specific IgE (sIgE) levels of variable intensity reflect the likelihood of an allergic reaction[5]. Due to the enhanced awareness of infection prevention and control during the COVID-19 epidemic, human social behaviors and health habits have significantly changed in a short period. A series of NPIs have been undertaken worldwide, including keeping social distance, wearing masks, hand hygiene, controlling crowd gathering, reducing going out, business suspension et al. We compared the incidence of allergy and concentrations of various allergen-sIgE before and during the COVID-19 pandemic to explore the impact of COVID-19 on allergic diseases. The present study enrolled children who came to the children's hospital of Zhejiang University between January 2019 and December 2020 for allergen detection. Children infected with COVID-19 were excluded. Inhaled and food allergen-sIgE antibodies were detected by the allergen detection kit of Hangzhou Zheda Dixun Biological Gene Engineering Co., Ltd. Data were analyzed using Mann-Whitney U test for continuous variables and Chi-squared test for categorical variables. P < 0.05 was defined as statistically significant. All statistical analyses were processed with PASW 22.0 statistical software (IBM Corporation).

A total of 41,648 specimens were collected in 2019, of which 17,590 (42.23%) were allergen positive. However, a total of 24,714 specimens were collected in 2020, of which 12,731 (51.51%) were allergen positive. The number of allergen-positive specimens in 2020 was significantly lower than in 2019 (P < 0.05). The number of allergen-positive specimens in the first ten months of 2020 was lower than that in the same period of 2019, especially in January and February. After that, the number of allergen-positive specimens tended to be the same in November, and the number of allergen-positive specimens in December 2020 was higher than that in 2019 (Fig. 1 a). Except for Beef, Mango, and Cashew nut, the number of positive specimens of various allergens in 2020 was significantly lower than that in 2019 (P < 0.05) (Fig. 1b, 1c). It can be concluded that NPIs during the COVID-19 outbreak significantly reduced the incidence of allergic diseases among children.

Fig. 1

The number of allergen-positive specimens before and during the COVID-19 pandemic. (a) The number of allergen-positive specimens each month before and during the COVID-19 pandemic. (b) The number of food allergen-positive specimens before and during the COVID-19 pandemic. (c) The number of inhaled allergen-positive specimens before and during the COVID-19 pandemic.

The concentrations of food allergen-sIgE antibodies in 2020 significantly decreased compared with that of 2019 (P < 0.05) (Fig. 2 a). A similar result was also obtained in inhaled allergens. The concentrations of their allergen-sIgE antibodies significantly decreased compared with that of 2019 (P < 0.05) (Fig. 2b). However, D.farinae/D.pteronyssinus, an indoor allergen, was an exception. The concentrations of its sIgE antibodies presented a significant increase in 2020 compared with that of 2019 (P < 0.05) (Fig. 2c). The decrease of antigen-sIgE concentrations may be attributed to the protective role of NPIs in avoiding exposure to allergens. NPIs reduce the risk of re-exposure to various allergens in children, thus alleviating the exacerbation of diseases. At the same time, staying at home for a long time increase the risk of exposure to the indoor allergen and prolong children's exposure time, which negatively impacts the prevention control of some allergic diseases[6]. The increased sIgE concentration of D.farinae/D.pteronyssinus supported this conclusion in the present study.

Fig. 2

The concentrations of allergen-sIgE antibodies before and during the COVID-19 pandemic. (a) The concentrations of food allergen-sIgE antibodies before and during the COVID-19 pandemic. (b) The concentrations of inhaled allergen-sIgE antibodies before and during the COVID-19 pandemic. (c) The concentrations of D.farinae/D.pteronyssinus sIgE antibodies before and during the COVID-19 pandemic. Abbreviation: sIgE, specific IgE.

To sum up, our study found that, in general, the incidence of allergic diseases in children during the COVID-19 epidemic was reduced, and the exacerbation of diseases in allergic patients was also reduced. A recent meta-analysis encompassing 22,159 subjects demonstrated by random effect model that compared to the same period before the COVID-19 pandemic, pediatric asthma control during the pandemic was characterized by the lower incidence of asthma exacerbation (OR=0.26, 95%CI: 0.14,0.48), and lower emergency department visits (OR=0.11, 95%CI: 0.04,0.26)[7]. The control of allergic diseases has been significantly improved during the pandemic. Therefore, it is reasonable to specify that changes in human life and the living environment caused by NPIS in COVID-19 have a critical influence on the prevalence and control of allergic diseases. First, owing to businesses suspension, parents spend more time on their children's diets, which unquestionably reduces their exposure to food allergens to a great extent[8]. Second, measures such as wearing masks, washing hands frequently, strengthening indoor ventilation, and maintaining social distance not only hindered the spread of SARS-Cov-2 but avoided children's contact with inhaled allergens[9]. Third, air quality was significantly improved during the blockade, and air pollutants were significantly reduced, which also avoided children's exposure to inhaled allergens[10]. To a certain extent, NPIs during the COVID-19 pandemic have played a protective role in reducing children's exposure to allergens. The specific measures controlling the occurrence and development of allergic diseases should be further studied.

In conclusion, during the COVID-19 pandemic, non-pharmaceutical interventions reduced children's incidence and exacerbation of allergic diseases.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of Competing Interest

All authors have declared that there is no conflict of interest.