Introduction

Allergic rhinitis (AR) is a common chronic inflammatory disorder of nasal mucosa, driven by immunoglobulin E (IgE)-mediated hypersensitivity to environmental allergens.¹ It is characterized by nasal congestion, sneezing, rhinorrhea, and nasal itching, and can substantially impair quality of life and reduce work productivity. In recent years, the global prevalence of AR has continued to rise, largely attributed to rapid urbanization, environmental pollution, and lifestyle changes.^2,3 In China, epidemiological data indicate a 6.5% increase in AR prevalence in recent years, with particularly high proportions reported in densely populated and highly industrialized urban areas.⁴

Shenzhen, a rapidly growing coastal metropolis in southern China, has a warm and humid subtropical climate. Combined with high population density and frequent human mobility, these conditions create a distinctive allergen exposure environment. A previous study showed that sensitization patterns in subtropical regions differ markedly from those in temperate climates, such as Europe, with higher sensitization to house dust mites, pronounced age-related variations, and only limited overlap in prevalent allergens across regions.⁵ While allergen sensitization has been investigated in several inland regions of China,^6,7 data from Shenzhen remain scarce, despite its unique geographic and demographic characteristics. To address this gap, the present study aimed to characterize the demographic features and allergen sensitization profiles of AR patients in Shenzhen. By analyzing serum-specific IgE (sIgE) levels, this study seeks to provide evidence-based insights to support improved prevention, diagnosis, and individualized management of AR in this region.

Methods

Study population

This retrospective study included AR patients who reported at the Department of Otorhinolaryngology – Head and Neck Surgery, Shenzhen University General Hospital, between January 2022 and December 2022. Inclusion criteria were as follows: (1) presence of typical AR symptoms, such as sneezing, nasal congestion, rhinorrhea, and nasal itching; (2) diagnosis confirmed by clinical history and physician evaluation; (3) availability of sIgE test results; and (4) permanent residents of Shenzhen, China. Exclusion criteria included: (1) comorbid chronic rhinosinusitis or nasal polyps; (2) autoimmune or systemic diseases that may affect immune responses; and (3) incomplete clinical or laboratory data.

Allergen-specific IgE testing

Peripheral venous blood samples were collected from all patients and analyzed using the ImmunoCAP system (Phadia AB, Uppsala, Sweden). A total of 19 common allergens were tested, including dust mites, animal dander, pollens, and molds. A serum sIgE level ≥0.35 kU/mL was considered positive. Sensitization levels were classified into six classes based on sIgE concentration: class 1: 0.35–0.69 kU/mL, class 2: 0.70–3.49 kU/mL, class 3: 3.50–17.49 kU/mL, class 4: 17.50–49.99 kU/mL, class 5: 50.00–99.99 kU/mL, class 6: ≥100 kU/mL.⁸

Grouping and comparative analysis

Patients were stratified by gender (male vs. female), age (<14 years as pediatric group vs. ≥14 years as adolescent/adult group), and sIgE positivity level. The distribution of allergen sensitization was analyzed across these subgroups to explore demographic variations.

Statistical analysis

All statistical analyses were performed using GraphPad Prism version 8.0.2 (GraphPad Software, San Diego, CA, USA). Categorical data were expressed as percentages. Group comparisons were conducted using the Chi-square test; P < 0.05 was considered statistically significant.

Results

General characteristics

A total of 3351 patients diagnosed with AR were included, comprising 1964 males (58.61%) and 1387 females (41.39%), with a male-to-female ratio of 1.42:1. Among them, 1731 patients (51.66%) were aged <14 years, while 1620 patients (48.34%) were adolescents/adults. Of the 3351 patients diagnosed with AR, the number of clinic visits peaked in August (530 cases) and was lowest in November (164 cases) (Figure 1).

Overall allergen sensitization profile

Among all patients, 2503 (74.69%) tested positive for at least one allergen-specific IgE. The most prevalent allergens were Blomia tropicalis (Bt) (66.58%), Dermatophagoides pteronyssinus (Dp) (66.01%), and Dermatophagoides farinae (Df) (59.27%). Other important indoor allergens included cockroach (28.86%), dog dander (21.70%), and cat dander (13.97%). The leading outdoor allergens were Ambrosia artemisiifolia (25.19%), Chenopodium album/Amaranthus retroflexus (18.50%), and Platanus acerifolia/Fraxinus (15.88%) (Figure 2).

Gender-based differences in allergen sensitization

In males, the top three allergens were Df (67.46%), Bt (67.31%), and Dp (61.20%). In females, Bt ranked first (65.54%), followed by Df (63.95%) and Dp (56.52%) (Figure 3A). Male patients had significantly higher sensitization proportions to Dp (χ² = 4.472, P < 0.05) and Df (χ² = 7.365, P < 0.05) than females. No significant gender differences were observed for other allergens (Table 1).

Age-based differences in allergen sensitization

In the pediatric group (aged <14 years), Df was the most prevalent allergen (70.08%), followed by Bt (67.76%) and Dp (64.12%). In the adolescent/adult group (aged ≥14 years), Bt (65.31%) ranked first, followed by Dp (61.67%) and Df (54.07%) (Figure 3B). Notably, the sensitization proportions of leading allergens (Bt, Dp, and Df) declined with increasing age. Specifically, pediatric patients exhibited significantly higher sensitization to indoor allergens, including Dp (χ² = 25.996, P < 0.001), Df (χ² = 34.601, P < 0.001), cat dander (χ² = 42.993, P < 0.001), and dog dander (χ² = 71.698, P < 0.001). In contrast, adolescent/adult patients demonstrated higher sensitization to outdoor allergens, including pollens, such as silk (χ² = 34.861, P < 0.001), Artemisia (χ² = 10.166, P < 0.05), Poapratensis (χ² = 5.218, P < 0.05), and Acer negundo (χ² = 7.711, P < 0.05) as well as molds such as Aspergillus fumigatus (χ² = 25.583, P < 0.001) and Candida albicans (χ² = 4.573, P < 0.05) (Table 2).

Distribution of sIgE levels among allergen types

For Dp and Df, most patients exhibited class 3 sIgE levels (3.50–17.49 kU/mL). For Bt and cat dander, sensitization peaked at class 2 (0.70–3.49 kU/mL). For dog dander and cockroach, sensitization was mainly at class 1 (0.35–0.69 kU/mL). Sensitization to pollens and molds was predominantly at class 1 (0.35–0.69 kU/mL), indicating low-level responses (Figure 3C). The distribution of sIgE classes differed significantly among allergen types (χ² = 5487, P < 0.05) (Table 3).

Discussion

This study presents a comprehensive overview of the demographic characteristics and allergen sensitization profiles in patients with AR in Shenzhen, China. The results demonstrate that house dust mites—particularly Bt, Dp, and Df—are the predominant sensitizing allergens. This pattern aligns with the subtropical coastal climate of Shenzhen, characterized by warmth and high humidity, which provides optimal conditions for mite proliferation. These findings highlight the central role of dust mites in the pathogenesis of AR in this region and underscore the importance of targeted allergen surveillance and prevention strategies.

The prominence of Bt sensitization in this study is particularly noteworthy, as this allergen has been less frequently reported in northern China but appears to play a major role in subtropical regions, such as Guangdong. Historically, Df was reported as the leading allergen in Shenzhen between 2004 and 2015, followed by Dp, consistent with patterns observed across southern China.^9–11 Our findings, however, suggest a potential shift in the allergen spectrum, with Bt emerging as a dominant sensitizer. This trend may reflect advances in allergen detection techniques as well as environmental influences, including Shenzhen’s subtropical monsoon climate and the broader impact of global warming, which may favor Bt proliferation. In addition, although previous work from Guangzhou indicated rising sensitization to animal-derived allergens in association with urbanization and increased pet ownership,¹² our study found cockroach sensitization to be more prevalent than pet allergen sensitization in Shenzhen. This likely reflects the city’s warm and humid environment, which is highly conducive to cockroach survival. Together, these results underscore the importance of region-specific allergen surveillance, which is essential for guiding effective prevention measures and tailoring allergen-specific immunotherapy.

Previous studies have suggested that allergen sensitization patterns may differ between male and female patients with AR, potentially due to gender-related differences in immune regulation and the modulatory effects of sex hormones on disease-associated gene expression.^13,14 In line with this, our study found that male patients exhibited higher sensitization proportions to Dp and Df, indicating possible gender-related disparities in allergen exposure or immune responsiveness. These differences may be partly mediated by hormonal influences, as estrogen and progesterone enhance humoral and Th2-driven immune responses, whereas testosterone generally exerts immunosuppressive effects.¹⁵ Additionally, genetic and epigenetic factors, including X-linked immune regulatory genes, may contribute to gender-specific variations,¹⁶ and occupational or behavioral factors could further modulate allergen exposure.¹⁷ Further research is warranted to elucidate the biological mechanisms underlying these gender-based differences and their clinical implications.

In our study, the sensitization proportions of leading allergens declined with increasing age. Pediatric patients showed significantly higher sensitization to indoor allergens, including mites and animal dander, whereas adolescents and adults were more strongly sensitized to outdoor allergens, such as pollens and molds. These patterns align with longitudinal studies reporting an age-related decrease in allergen sensitization and serum sIgE levels,^18,19 probably attributable to immunosenescence, including thymic involution, reduced naïve T- and B-cell output, and lower IgE production.²⁰ In children, Th2-biased responses, reduced regulatory T-cell activity, and elevated IgE, combined with prolonged indoor exposure, predispose them to indoor allergens. In contrast, adolescents and adults show diminished reactivity to indoor allergens because of immunosenescence, while broader environmental exposure drives higher pollen and mold sensitization. Overall, these findings highlight the roles of immune maturation, senescence, and environmental factors in shaping allergen sensitization and support age-specific prevention and immunotherapy strategies.

With respect to sIgE distribution, most patients sensitized to Dp and Df exhibited moderate IgE concentrations (class 3), whereas Bt and cat dander peaked at class 2, and plant-derived allergens were largely associated with low-level sensitization. These distinctions may reflect differences in allergenic potency, environmental exposure, and host immune responsiveness. Recognizing such patterns is clinically relevant, as they provide insights into the likelihood of symptomatic disease and can guide the selection and prioritization of allergens in immunotherapy protocols.

Despite its strengths, this study has several limitations. First, as a single-center retrospective analysis, the potential for selection bias cannot be excluded, and temporal trends in sensitization could not be assessed. Second, clinical correlations—such as symptom severity, validated scoring systems (e.g., VAS, TNSS), or treatment outcomes—were not incorporated, restricting the ability to determine the clinical significance of sensitization. Future prospective, multicenter studies with integrated clinical data are warranted to validate and extend these findings.

Conclusion

Dust mites—particularly Bt—represent the predominant allergens among AR patients in Shenzhen, with cockroach sensitization exceeds that of pet dander. Allergen patterns differ by age, gender, and sIgE level: males tend to show higher reactivity to Dp and Df, and the overall sensitization to leading allergens declines with increasing age. Pediatric patients are more affected by indoor allergens, whereas adolescents and adults are more affected by pollens and molds. While most allergens elicit low to moderate sIgE levels, mites generally induce stronger sIgE responses. These findings highlight the importance of region-specific allergen surveillance to refine diagnosis, guide individualized allergen avoidance, and optimize immunotherapy strategies for AR.