The rapidly increasing prevalence of allergic rhinitis (AR), allergic asthma, and other allergic diseases in children has attracted global attention. The International Study of Asthma and Allergic Rhinitis in Children (ISAAC) [1] reported that the prevalence of AR in children aged 6 - 7 years was 8.5%, and 14.6% in those aged 13 - 14 years, with significant regional and international variations. Epidemiological studies in various regions of China indicate that the prevalence of AR in children ranges from 18.10% to 49.68%, with confirmed prevalence rates between 10.80% and 21.09%, showing an increasing trend [2] - [4] . The onset of AR is closely related to environmental factors, and the types of allergens differ by region. In northern China (including north-western and north-eastern areas), weed pollen is the primary allergen [5] - [7] , whereas in the southern regions (East, Central, and South China), dust mites and house dust mites are the predominant allergens [7] - [10] . Given China’s vast geographical expanse and significant regional variations in environmental, climatic, economic, and hygiene conditions, the composition of allergens varies considerably across different areas [5] .

Shenzhen, as a major immigrant city in southern China, has a diverse population that includes both northern and southern migrants, resulting in a complex distribution of allergens. However, to date, no studies have reported the distribution of allergen-specific IgE (sIgE) in children with AR in this region. Early identification of potential allergens is crucial for clinicians and parents, as it provides a basis for developing more effective and safer prevention and treatment strategies for AR. The diagnosis of IgE-mediated allergic diseases relies on both ex vivo and in vivo testing of allergen extracts to detect sensitization to specific allergens, with the final diagnosis confirmed through correlation with the clinical history [11] . Due to its safety and versatility, including its applicability regardless of age or recent drug use, sIgE testing is a widely used laboratory marker to assess atopic status in children and identify specific allergens to which they may be sensitized. This study reports the analysis of in vitro sIgE results for 28 common allergens in 3901 children with AR in Shenzhen, stratified by season, gender, and age group.

Allergic rhinitis (AR) is a common condition in children and adolescents that significantly affects sleep, school performance, and quality of life. Potential triggers include airborne pollen, moulds, dust mites, and animal dander [13] . Inhalant allergens and food allergens undergo a series of pathophysiological processes to produce allergen-specific IgE (sIgE) [14] - [16] . This sIgE enters the nasal mucosa via the circulatory system and binds to high-affinity IgE receptors (FcεRI) on the surface of local mast cells and basophils, thereby sensitizing the individual. Upon re-exposure to the same allergen, the sensitized organism initiates a cascade of pathological reactions, including vasodilation, increased vascular permeability, exudation of vascular contents, mucus production, sensory nerve stimulation, and the localized aggregation of inflammatory cells in the nasal mucosa. These processes result in the clinical symptoms of AR [17] . The diagnosis of IgE-mediated allergies primarily relies on both in vivo and in vitro testing of allergen extracts to assess whether there is “sensitization” to specific allergens, followed by confirmation of an “allergy” based on consistency with the patient’s clinical history [11] . However, sensitization patterns may vary across different genders, age groups, and seasons. Therefore, exploring the distribution of common allergen positivity, based on these factors, in children with allergic rhinitis is significant for the individualized management and control of AR in different populations.

The number of 3901 children with allergic rhinitis in this study who had allergen positivity amounted to 2742 cases or 70.3%. The top three allergens with the highest positive rates in the inhalation group were house dust mites/powder mites, dog dander, and cat dander. The top three allergens with the highest positive rates in the food group were milk, egg white, and beef. More children were positive for multiple allergens simultaneously. The reasons for this may be related to the underdeveloped immune system in children, which results in immune tolerance and characteristics of cross-sensitization to allergens [18] . Additionally, Shenzhen, with its subtropical climate, provides an environment conducive to the proliferation of dust mites, while the humid air promotes the spread of mold spores. Therefore, in the diagnosis and management of allergic rhinitis, it is essential to consider the impact of multiple allergens and develop personalized prevention and treatment strategies based on the individual characteristics of children.

This study found that dust mites, milk, egg white, and dog dander were the most common allergens across all seasons, with dust mites showing the highest positivity, particularly in autumn (45.5%). Significant seasonal variations were observed for dust mites and several other allergens (P < 0.05), but no clear pattern was identified for most allergens. Autumn and winter are the peak seasons for the dispersion of many plant pollens, particularly tree and grass pollens. The release of these allergens coincides with higher humidity and lower temperatures, which facilitate the accumulation of airborne allergens, consistent with findings from previous studies [19] . Additionally, the spread of fungal spores tends to increase during these seasons, as higher humidity levels provide favorable conditions for fungal growth. This observation contrasts with prior research, which may be attributed to the influence of monsoon climates in northern China [20] . Milk and egg proteins are common food allergens in children, which show higher sensitization rates, especially during infancy and early childhood. Moreover, dust mites primarily inhabit human living environments, such as bedding, carpets, and furniture, where mite concentrations tend to fluctuate with seasonal changes, thereby influencing allergen sensitization rates.

Domestic studies have found no significant gender difference in allergen distribution [21] . In this study, the overall allergen positivity rates were 71.1% for males and 68.7% for females, with no significant difference (P > 0.05). However, certain allergens, such as dust mites, cockroaches, tree pollen, house dust, wormwood, shrimp, crabs, lobster/scallops, and mutton, showed higher positivity rates in males (P < 0.05). Androgens, including testosterone, may enhance immune responses to some extent, leading to a higher sensitivity in males when exposed to allergens. Additionally, females tend to spend more time in domestic environments, where they may be more frequently exposed to indoor allergens like house dust and pet dander. The gender differences in sensitivity to these indoor allergens may not be as pronounced as those observed with outdoor allergens.

A domestic study in Beijing identified the top four inhalant allergens as Candida, Penicillium, Artemisia, and cat dander [22] . In contrast, the present study found that the highest positivity rate was for dust mites, which is a major allergen in children with allergic rhinitis. Previous research in China has reported dust mite sensitization rates as high as 72.8% in children with allergic rhinitis [23] . In this study, the positivity rate for house dust mite/dust mite was 42.1%, with rates increasing by age: 17.0% in the 0 - 3 year age group, 43.5% in the 3 - 6 year group, and 58.1% in the 6 - 14 year group. Similarly, other inhalant allergens, including dog dander, cat dander, cockroaches, house dust, ragweed, and Humulus lupulus, also showed a trend of increasing positivity with age. As children age, their immune system gradually establishes immune memory responses, particularly in those over 3 years old, leading to a more pronounced immune reaction to various common allergens, which in turn results in an increase in the positivity rate. Additionally, with the expansion of their activity range, the likelihood of exposure to outdoor allergens also increases.

With the development of China’s economy, food choices have become more diverse, and allergic diseases related to food allergies have gained increasing attention. Over the past two decades, the prevalence of milk protein allergy in infants and children in China has risen from 1.6% to 5.7% [24] . Similarly, this study found that the three most common food allergens were milk, egg white, and beef, with positivity rates of 33.8%, 19.4%, and 12.7%, respectively, corresponding to 1322, 758, and 497 cases. These findings indicate that milk remains a major allergen for children with allergic rhinitis. Domestic research suggests that most IgE-mediated milk protein allergies in infants are tolerated by age 3 [25] and our study also observed that the highest milk allergy positivity rate was found in the 0 - 3 year age group, with a decreasing trend as age increased. However, it is noteworthy that even in the 6 - 14 year age group, a significant positive rate of 24.4% was still observed. This is consistent with studies in Europe and the United States [26] .

The present study also revealed the distribution of strong positive allergens: 824 or 21.1 per cent were sensitised at level 4 or higher. The house dust mite/dust mite was the most numerous of them, with 768 cases, and accounted for an absolute proportion (93.2%) of the strong positive allergens. Therefore, dust mite desensitisation in children with allergic rhinitis is of great significance, and subcutaneous immunotherapy has been used in the treatment of AR for more than 100 years, which not only significantly improves clinical symptoms, reduces medication usage, and enhances quality of life, but also demonstrates stable long-term efficacy, preventing the progression of AR to asthma and reducing the emergence of new allergens [27] . However, attention needs to be paid to the assessment of efficacy in children who are positive for multiple allergens. The highest rate of strong positivity in the food group was milk, with only 30 cases, but most of them were children after 3 years of age, which suggests that we should consider the degree of sensitisation to milk and the balance of nutritional requirements when guiding the dietary modification of children with milk-sensitised rhinitis, as well as be mindful that although the proportion of children sensitised to milk decreases after the age of 3 years, an increase in children with a high degree of sensitisation may still occur.

In summary, house dust mite/dust mite and dog hair dander were the main inhalation allergens in children with allergic rhinitis in Shenzhen, while milk and egg white were the main food allergens. The positivity rate of the major inhalation allergens increased with age, while the positivity rate of food allergens, such as milk and egg white, tended to decrease with age. However, milk may show a higher proportion of strong positive sensitisation in those who continue to have a high rate of positivity after the age of 3 years.

1) This study is a single-center retrospective analysis, which only include AR children who presented with allergic symptoms at the hospital and underwent allergen-specific IgE (sIgE) testing, rather than using data from the general population. 2) The study did not consider factors such as the family’s socioeconomic status or psychological state, which may limit the ability to establish potential associations between these factors and sensitization to allergens; 3) As this study primarily explores co-sensitization, it does not account for the potential impact of cross-sensitization on the results.