Introduction

The global prevalence of allergic sensitization to furry animals has increased markedly over recent decades.1 Sensitization to dog and/or cat allergens was observed in 10–20% of individuals and has been implicated with the development of respiratory allergies including asthma and allergic rhinitis (AR).2 Pet allergens are ubiquitous and can be detected in public environments—including schools and workplaces—even in the absence of direct animal contact.3 With the growing popularity of indoor pet ownership, especially in urban settings, the risk of population-level exposure and subsequent sensitization to dog- and cat-derived allergens is likely to increase further.

Currently, the World Health Organization and International Union of Immunological Societies (WHO/IUIS) listed 8 distinct dog allergen components (Canis familiaris, Can f 1-Can f 8). Among these, Can f 1, Can f 2, Can f 4, and Can f 6 belong to the lipocalin family of proteins. The major allergen Can f 1, produced in the salivary and sebaceous glands, has been shown to sensitize over 70% of dog-allergic individuals.4 Sensitization to Can f 1 has been linked to an increased risk of allergic respiratory symptoms and asthma.5 However, these findings have been predominantly derived from Western populations, and their generalizability to other regions, such as those in the tropics, remains uncertain.

In the Singapore/Malaysia Cross-sequential Genetics and Epidemiological Study (SMCGES) population, we have previously demonstrated that allergic diseases in this region are largely driven by sensitization to house dust mite (HDM) allergens.6 Sensitizations to other tropical environmental allergens, such as fungus and tree pollen, have also been associated with increased allergic symptoms and exacerbation in this population.7,8 Moreover, the presence of domestic pets in the household has been shown to be significantly associated with increased respiratory-related allergy symptoms.9–11 Despite these observations, the association between dog dander sensitization and allergic disease manifestations has not been comprehensively examined in this population.

In this study, we performed a comprehensive serological assessment of serum-specific IgE (SSIgE) responses to 38 common inhalant and seafood allergen sources—including HDM, pet dander, fungi, pollens, insects, crustaceans, fish, and mollusks—among 736 participants of the SMCGES serological assessment sub-cohort. We investigated whether pre-existing sensitization to inhalant and seafood allergen sources was associated with detectable SSIgE responses to the major dog allergen Can f 1. We also evaluated the relationship between Can f 1 sensitization and asthma-related symptom frequency and exacerbation risk in this population.

Materials And Methods Study Design

To evaluate the prevalence of specific IgE responses to HDM and animal dander allergens in the Singapore/Malaysia population, we first analyzed a serological screening dataset from a previously established, consecutively recruited serum biobank comprising 1,069 legacy samples collected from allergic patients at local hospitals in Singapore. The samples were obtained between 2000 and 2001.

Thereafter, for a more comprehensive serological assessment of 38 common inhalant and seafood allergen sources in Singapore/Malaysia, we recruited a cross-sectional cohort of young adults from the general populations of Singapore and Malaysia as part of the ongoing SMCGES. Recruitment sites were three universities: the University of Tunku Abdul Rahman (UTAR), Malaysia (February 2016–October 2018); Sunway University (SU), Malaysia (November 2019–present); and the National University of Singapore (NUS), Singapore (August 2005–present). Study methodology and descriptive information on the SMCGES population have been reported previously.9,10,12

SMCGES participants completed an investigator-administered questionnaire capturing demographic data, medical history, symptom severity, and exacerbation frequency of respiratory and skin allergies. The questionnaire was developed based on the Allergic Rhinitis and Its Impact on Asthma (ARIA) guidelines13 and the International Study of Asthma and Allergies in Childhood (ISAAC) protocol.14 Ethnicity was determined by self-report. As previously demonstrated via principal component analysis (PCA), the majority of Chinese participants from the SMCGES cohort cluster closely with the 1000 Genomes Han Chinese (CHB) population.15 Individuals with asthma and other allergic diseases had their condition positively diagnosed by a physician. Allergic rhinitis (AR) was defined as having at least two major symptoms including nasal congestion, rhinorrhea, nasal itching, and sneezing (based on 2008 guidelines set by the ARIA consortium) (Bousquet et al, 2008). Atopic dermatitis (AD) was defined according to the Hanifin-Rajka Criteria,16 which require the presence of a persistent itchy rash affecting flexural areas.

Participants also underwent a skin prick test (SPT) during the recruitment process, as a part of our prior investigation to assess their sensitization to house dust mite (HDM) allergen sources. HDM was previously identified as the most common inhalant allergen and predominantly drives allergic reactions in this region.6 The allergen panel (0.1 mg/mL each) included two HDM species (Blomia tropicalis, Blo t and Dermatophagoides pteronyssinus, Der p). Histamine (10 mg/mL, Unison Collaborative, Singapore) was included as the positive control, while 0.9% saline was included as a negative control in the SPT. A positive SPT reaction was defined as a wheal diameter of ≥3 mm, measured 15 minutes after pricking.

Serological Assessment

To evaluate if pet dander sensitization is also an important contributor to the development of allergic diseases, we further assessed SSIgE levels to Can f 1 in the SMCGES serological assessment sub-cohort (n = 736). In this cohort, 10 mL of whole blood was collected from each participant, and serum samples were then extracted by centrifugation. SSIgE to crude allergen protein extracts was measured using a previously described immuno-dot blot assay.7,8,17–19 Briefly, crude protein extracts (0.25 mg/mL) were dotted in duplicate onto nitrocellulose membranes (Cytiva, USA). Bovine serum albumin (BSA, 1 μg) and phosphate-buffered saline (PBS) were included as controls. Membranes were blocked with PBS containing 0.1% Tween-20 for 1 hour, incubated overnight at 4 °C with diluted serum (1:10 in PBS), washed with PBS containing 0.05% Tween-20, and then probed for 2 hours with alkaline phosphatase–conjugated anti-human IgE antibodies (Sigma-Aldrich, USA). Signals were visualized with NBT/BCIP substrate (Thermo Fisher Scientific, USA) for 10 minutes and quantified using Syngene imaging software with background subtraction. Serially diluted IgE standards (ranging from 1000 IU/mL to 0.195 IU/mL, National Institute for Biological Standards and Controls, UK) were additionally included for interpolating the spot intensity into IU. The SSIgE titers were categorized into non-detectable (< 0.35 IU/mL), Class 1 (0.35–0.69 IU/mL), Class 2 (0.7–3.49 IU/mL) Class 3 (3.5–17.49 IU/mL), Class 4 (17.5–49.9 IU/mL), Class 5 (50–100 IU/mL), and Class 6 (> 100 IU/mL). To ensure analytical accuracy and reproducibility, these results were validated against automated gold-standard platforms, including the ImmunoCAP Specific IgE Assay (Phadia, Sweden) and Immulite (Siemens Healthineers, Germany). This validation was performed on a random subset of 127 serum samples across 12 distinct allergen sources (including HDM, pollens, fungi, and seafood). The results demonstrated high concordance between the platforms, with Spearman correlation coefficients (rs) exceeding 0.85 for all allergen sources tested.

The serological assessment panel for the preliminary study of 1,069 legacy serum samples comprised six crude allergenic extracts, including Blo t, Der p, Dermatophagoides farinae (Der f), dog dander, cat dander, and cow dander.

The serological assessment panel for the SMCGES study included 38 common allergen sources, consisting of Blo t, Der p, Der f, natural dog dander (specific allergen Can f 1), natural cat dander (Felis domesticus 1; specific Fel d 1), cockroach allergen sources (Periplaneta americana, Per a and Blatella germanica, Bla g), pollen allergen sources—including grasses from Panicoids (Poales Order, Panicoideae Subfamily: Sorghum halepense), Pooids (Poales Order, Pooideae subfamily: Phleum pratense, Lolium pratense, and Lolium perenne), Chloridoids (Poales Order, Chloridoideae Subfamily: Cynodon dactylon), and weed species (Brassicales Order, Brassicoideae Subfamily: Brassica spp.; Asterales Order, Asteroideae Subfamily: Ambrosia artemisiifolia, and Helianthus annuus)—as well as fungal allergen sources (Aspergillus spp., Cladosporium spp., and Penicillium spp.) and 24 seafood allergen sources.

These 24 types of seafood allergen sources included crustaceans (Portunus pelagicus, Crangon crangon, Penaeus monodon, and Litopenaeus vannamei), mollusks (Cerastoderma edule, Uroteuthis chinensis, Haliotis planata, Paphia undulata, Strombus turturella, Perna viridis, Meretrix lyrata), and fishes (Salmo salar, Sillago parvisquamis, Thunnus thynnus, Lepisma saccharinum, Epinephelus tauvina, Gadus morhua, Xenobrama microlepis, Selaroides leptolepis, Channa micropeltes, Centropristis striata, Polydactylus sexfilis, Chanos chanos, Hypanus americanus). Participants’ total serum IgE levels were estimated as the sum of all 38 allergen source-specific IgE levels assessed in the SMCGES serological cohort. While a total serum IgE level of > 100 IU/mL is a common clinical threshold for identifying high atopic risk,20,21 this absolute cut-off was not applicable to our dataset, as total IgE was estimated via the sum of specific IgE levels. To accurately reflect the atopic distribution within this cohort, participants were instead categorized into quartiles (Q1–Q4) based on their estimated total serum IgE levels, using the 25th, 50th, and 75th percentiles as internal thresholds.

Crude inhalant allergenic extracts were purchased from Stallergenes Greer (USA), and crude seafood allergenic extracts were obtained from local markets in Singapore. All crude extracts were prepared by homogenization using a mortar and pestle, followed by centrifugation at 10,000 × g for 10 minutes. Natural dog dander (specific allergen Can f 1) and cat dander (specific allergen Fel d 1) were sourced from Indoor Biotechnologies Inc. (UK).

Statistical Analysis

All statistical analyses were performed using R software (version 3.6.1; R Foundation for Statistical Computing, Vienna, Austria). Categorical variables, including the presence of detectable SSIgE to inhalant and seafood allergen sources, were evaluated using multivariable logistic regression. Models were adjusted for age, sex, ethnicity, smoking status, and the presence of atopic comorbidities (AR and AD). Dose-response relationships between Can f 1-specific IgE ImmunoCAP classes and quartiles of total IgE concentrations were evaluated using a Cochran–Armitage test for trend in proportions. Serum-specific IgE concentrations were log10-transformed to minimize skewness. Normality was assessed through visual inspection of Normal Q-Q plots and the Shapiro–Wilk test. Although the Shapiro–Wilk test indicated a departure from normality—a common occurrence in large datasets due to high statistical power22—the Q-Q plots confirmed the transformed data were suitable for parametric testing (Figure S1). Accordingly, associations between Can f 1-specific IgE levels and asthma-related outcomes were analyzed using independent-sample t-tests. All statistical tests were two-tailed, and p-values were adjusted for multiple comparisons using the Benjamini-Hochberg False Discovery Rate (FDR) procedure.23 An FDR-adjusted p < 0.05 was considered statistically significant.

Results Dog Dander Can f 1-Specific IgE Profile and Association with IgE Responses to Common Inhalant and Seafood Allergen Sources

We first performed a preliminary assessment of SSIgE responses to common aeroallergen sources, including HDM and animal dander, using data from a previously collected, unbiased, and consecutive serum biobank comprising 1,069 legacy serum samples from allergic patients at local hospitals in Singapore. In this cohort, 85.2% of patients possessed detectable SSIgE titers to at least one of the three HDM allergen sources, including Der p (75.5%), Der f (70.3%), and Blo t (72.8%, Figure S2A). High frequencies of detectable SSIgE responses to animal dander were also observed, with more than 50% of patients showing specific IgE reactivity to dog (60.1%), cat (53.4%), and cow dander (73.4%, Figure S2A). We speculate that the high sensitization rate to crude animal dander extracts may be attributable to cross-contamination with HDM allergens, as demonstrated by a significant moderate correlation between SSIgE levels to HDM and animal dander in this cohort (Figure S2B). Consequently, to avoid the overestimation of the animal dander specific IgE responses, the specific major dog allergen Can f 1 was used in subsequent serological assessment to evaluate SSIgE responses to dog dander.

Next, we evaluated SSIgE levels to common inhalant and seafood allergen sources in the SMCGES serological assessment sub-cohort. A total of 736 young adults (mean age = 21.72 ± 5.89 years, 42% male, 60.9% Chinese, Table S1) were assessed for SSIgE responses to HDM, pet dander, cockroach, pollen, fungus, and seafood allergen sources. SSIgE reactivity to HDM allergen sources was the most prevalent, with 80.0% of participants showing detectable responses to at least one type of HDM allergen sources (Figure 1A and B). Consistently, skin prick testing identified 64.7% of individuals as HDM-sensitized (Table S1). Frequencies of detectable SSIgE responses (> 0.35 IU/mL) to other allergen sources were comparable to our previously reported results (Figure S3).8

Figure 1 Allergen sensitization profile of 16 common inhalant allergens in the SMCGES population. (A) Serum specific immunoglobulin-E (SSIgE) titers (as IU/mL) to inhalant allergens include three HDM species (Dermatophagoides pteronyssinus, Dermatophagoides farinae, and Blomia tropicalis), and dog dander (native Canis familiaris 1, Can f 1 protein). SSIgE titers were assessed on 736 individuals from the Singapore/Malaysia Cross-sequential Genetics and Epidemiological Study (SMCGES) serological assessment sub-cohort. *: Median and interquartile range (IQR) values were shown for individuals with detectable SSIgE (Class 1+, > 0.35 IU/mL) against each allergen. (B) The percentage of individuals possessing SSIgE sensitization to HDM or Can f 1 allergen was categorized into 4 groups based on ImmunoCAP-defined classes (non-detectable, Class 1, Class 2, and “Class 3 and above”). (C) Associations between pre-existing SSIgE response (> 0.35 IU/mL) to common allergens and Class 1+ (> 0.35 IU/mL) SSIgE sensitizations to dog dander (Can f 1) allergen. Multivariable logistic regression models adjusted for age, sex, and ethnicity were used to test for significant associations. *: p<0.05; **: p<0.01; ***: p<0.001; ****: p<0.0001. (D) Detectable SSIgE sensitization to Can f 1 (> 0.35 IU/mL) was categorized into 3 groups based on ImmunoCAP-defined classes (Class 1, Class 2, and “Class 3 and above”) and compared across 4 quartiles (Q1 to Q4) of total serum IgE levels. Chi-squared trend tests were performed to assess the significance of dose-response relationships (χ2 = 92.436, p<0.0001). ****: p<0.0001. For (B) and (D), the ImmunoCAP classes are defined as: non-detectable (< 0.35 IU/mL), Class 1 (SSIgE 0.35–0.69 IU/mL), Class 2 (SSIgE 0.7–3.49 IU/mL), or Class 3 and above (SSIgE > 3.5 IU/mL).

Detectable SSIgE to Can f 1 was observed in 13.5% of participants (Figure 1A and B). Among Can f 1 sensitized subjects, the interquartile range (IQR) of detectable Can f 1-specific IgE levels was 0.53–3.17 IU/mL, indicating predominantly low-grade Class 1–2 reactions (Figure 1A). Individuals with pre-existing Class 1+ SSIgE response to common inhalant allergen sources, such as HDM, were significantly more likely to exhibit Can f 1 sensitization (p=0.00454, adjusted odds ratio [aOR]=3.32, 95% confidence interval, CI=1.54–8.30, Figure 1C). Furthermore, individuals who demonstrated cockroach (Per a or Bla g)– and cat dander (Fel d 1)–specific IgE reactivity in addition to HDM sensitization had an even higher risk of Can f 1 sensitization (p=0.000165, aOR=4.19, 95% CI=1.95–8.75, Figure 1C). Expanding the analysis to include SSIgE responses to pollen, fungal, and seafood allergen sources revealed a progressive increase in the risk of Can f 1 sensitization, reaching up to a 5.5-fold higher risk among polysensitized individuals, compared with those lacking any pre-existing Class 1+ SSIgE responses to common allergen sources (p<0.0001, aOR=5.54, 95% CI=2.43–12.41, Figure 1C). Collectively, these findings indicate that atopic individuals with polysensitization to multiple inhalant and seafood allergen sources exhibit a substantially higher frequency of Can f 1-specific IgE reactivity in this population.

In the Singapore/Malaysia population, we have previously demonstrated that HDM sensitization drives atopy and is strongly associated with serum total IgE levels.6 To further examine the relationship between overall atopy and Can f 1 sensitization, total IgE levels were evaluated as the sum of specific IgE levels against 38 allergen sources assessed in this cohort. When participants were stratified by quartiles of total IgE (Q1–Q4; representing low to high IgE), a dose-dependent increase in the frequency of Class 1+ SSIgE responses to Can f 1 was observed (Chi-squared trend test, p<0.0001; Figure 1D). These findings indicate that Can f 1 sensitivity is more common among individuals with elevated total IgE and underlying atopy.

Association Between Can f 1-Specific IgE and Asthma Symptom Severity and Exacerbations

Having demonstrated a substantial rate of detectable SSIgE to Can f 1 in this population, we next evaluated its associations with allergic disease outcomes. In the SMCGES serological assessment sub-cohort (n=736), the frequency of asthma, allergic rhinitis, and atopic dermatitis were 12.4%, 42.3%, 22%, respectively (Table S1). Detectable SSIgE to Can f 1 was not significantly associated with asthma, AR, or AD (p>0.05, Figure S4A–C).

Nevertheless, among asthmatic subjects (n=91), Can f 1-specific IgE levels were significantly higher in those reporting asthma-related symptoms in the past 12 months, including wheezing (p=0.005), daytime asthma attacks (p=0.019), and nighttime asthma attacks (p=0.033; Figure 2A–C). Elevated Can f 1-specific IgE was also associated with recent asthma exacerbations, defined as asthma-related school absenteeism, clinic or emergency department visits, or hospitalization (p<0.05; Figure 2D and E). No significant associations were observed between Can f 1-specific IgE and cough-variant or exercise-induced asthma (data not shown).

Figure 2 Association between Can f 1 specific IgE response and Asthma Symptom Severity and Exacerbation Frequency. Associations of Can f 1 specific IgE responses with recent (past 12 months) asthma-related symptoms and exacerbations including (A) wheezing, (B) daytime asthma attacks, (C) nighttime asthma attacks, (D) asthma-related school absenteeism, and (E) any asthma-related exacerbation events were assessed on 736 individuals from the SMCGES sub-cohort. Statistical significance was assessed using independent-sample t-tests. All p-values were adjusted for multiple comparisons using the Benjamini-Hochberg procedure.23 The mean ± 1 standard deviation was shown in each boxplot. *: p<0.05; **: p<0.01.

Associations Between Can f 1-Specific IgE Responses and Asthma Severity Among HDM-Sensitized Individuals

Given that respiratory allergies in tropical urban environments such as Singapore are primarily driven by HDM sensitization,6 we further evaluated whether Can f 1-specific IgE sensitization was associated with asthma outcomes beyond its co-occurrence with HDM reactivity.

Among HDM-sensitized individuals (n=476; mean age = 21.19 ± 4.15 years; 49.4% male; 66.4% Chinese; Table S1), Can f 1-specific IgE was not associated with overall asthma, AR, or AD prevalence (p>0.05; Figure S5A–C). However, Can f 1-specific IgE levels were significantly higher in those with recent wheezing (p=0.001), daytime asthma attacks (p=0.024), and nighttime asthma attacks (p=0.015; Figure 3A–C). Similarly, Can f 1 SSIgE levels were elevated among individuals reporting any recent asthma exacerbation event, including school absenteeism, clinic visits, emergency care, or hospitalization (p<0.05; Figure 3D and E).

Figure 3 Association between Can f 1 specific IgE response and Asthma Symptom Severity and Exacerbation Frequency among HDM-sensitized individuals. Associations of Can f 1 specific IgE responses with recent (past 12 months) asthma-related symptoms and exacerbations including (A) wheezing, (B) daytime asthma attacks, (C) nighttime asthma attacks, (D) asthma-related school absenteeism, and (E) any asthma-related exacerbation events were assessed on 476 HDM-sensitized individuals from the SMCGES sub-cohort. Statistical significance was assessed using independent-sample t-tests. All p-values were adjusted for multiple comparisons using the Benjamini-Hochberg procedure.23 The mean ± 1 standard deviation was shown in each boxplot. *: p<0.05; **: p<0.01.

Together, these findings indicate that Can f 1-specific IgE sensitization is distinctly associated with asthma symptom burden and exacerbation frequency, even in the presence of HDM sensitization.

Discussion

This cross-sectional study demonstrated that pre-existing sensitization to common inhalant and seafood allergen sources was associated with an enhanced specific IgE response to the major dog allergen (Can f 1), suggesting possible co-sensitization or a heightened atopic immune milieu that facilitates broader allergen reactivity. Importantly, Can f 1 sensitization was associated with asthma-related wheezing, higher attack frequency, and increased risk of asthma exacerbation, representing a significant clinical correlate of asthma severity that persists among HDM-sensitized individuals. These findings indicated that SSIgE responses to this allergen component are linked to greater asthma morbidity in the SMCGES population, which is in line with previous observations from Western cohorts showing associations between pet allergen sensitization and asthma symptoms.5,24 Overall, our results suggested that Can f 1 sensitization may serve as a biomarker of asthma exacerbation risk in the tropical environments of Singapore and Malaysia.

In the tropical urban environment of Singapore and Malaysia, allergic responses are predominantly driven by sensitization to HDM allergens, with 80.0% of participants exhibiting detectable serum-specific IgE (SSIgE) responses to HDM allergen sources (Figure 1A and B). This finding is consistent with our previous observations.6–8 HDM allergens are known to be nearly ubiquitous in tropical households, owing to the warm and humid climate that favors their proliferation.25 Similarly, dog dander allergen (Can f 1) has also been detected in more than half of surveyed indoor households, with significantly higher concentrations found in homes with current pet ownership.11,26 Further, we also demonstrated previously that pet ownership was significantly associated with the risk of respiratory allergies.9–11 Collectively, these findings suggest that frequent environmental exposure to pet dander allergens is associated with the substantial prevalence of Can f 1-specific IgE sensitization observed in our cohort and its association with higher asthma morbidity.

Importantly, despite the established relationship between pet ownership and increased indoor Can f 1 levels, we did not observe a significant association between current dog ownership and Can f 1-specific IgE sensitization in the SMCGES serological sub-cohort (data not shown). This finding is consistent with prior reports demonstrating the widespread environmental dissemination of pet allergens, which can be detected in public spaces and in homes without resident animals due to passive transfer via clothing and shared environments.3 In the tropical urban context, such ubiquitous exposure may diminish the discriminatory effect of direct pet ownership on sensitization risk, suggesting that community-level environmental exposure—rather than household ownership alone—may play a more prominent role in shaping Can f 1 sensitization patterns. Future longitudinal studies incorporating quantitative environmental allergen measurements alongside immunologic and clinical outcomes are needed to clarify exposure–response relationships in tropical settings. Such approaches may also help elucidate the biological mechanisms through which community-level pet allergen exposure influences asthma severity independent of household ownership.

In our work, the association between pre-existing sensitization to inhalant allergen sources, including dust mite, pollens, and fungi, and detectable SSIgE to Can f 1 may reflect co-sensitization rather than direct molecular cross-reactivity. The structural similarity between Can f 1 and these non-mammalian allergen sources (dust mite, fungi, pollen, and seafood) tends to be low, which undercuts the likelihood of strong cross-reactivity by the standard criterion of >50% identity.27 Further, while cross-reactivity among mammalian lipocalins (dog, cat, and horse) has been well-documented due to their structural similarities,27,28 previous findings suggested low to none cross-reactivity exist between dog and cat dander allergens in overall.29,30 Therefore, the association of pre-existing inhalant or seafood sensitization with higher SSIgE to Can f 1 level likely reflects an underlying high atopic propensity or allergen-load effect in this population.

The present findings should be interpreted with the following limitations considered. Firstly, due to the limitations of cross-sectional design, the Can f 1-specific IgE levels were only assessed for a specific time-point. Studies have demonstrated an increasing rate of pet sensitization with increasing age.31,32 Age-related sensitization patterns should be further investigated in a longitudinal cohort of the SMCGES population. Furthermore, while we adjusted for key demographics and comorbidities, our multivariable models did not account for other potential confounders—such as environmental air pollution (PM2.5) and adherence to asthma controller therapy—which may independently influence asthma symptom severity and exacerbation risk. Additionally, we are also unable to determine whether cross-reactivity exists across Can f 1 and other seafood and inhalant allergens due to the limitation of serum volume provided by study subjects. Furthermore, it is important to note that the associations between Can f 1 sensitization and asthma outcomes were primarily observed within the HDM-sensitized subgroup. Due to the near-complete penetrance of HDM sensitization in our tropical cohort,6 there was insufficient statistical variance to adjust for HDM status in multivariable models without significant multicollinearity. Consequently, while Can f 1 appears to be a distinct risk factor for symptom severity in our population, its statistical independence from HDM sensitization should be further validated in cohorts with lower HDM prevalence. Future studies are warranted to address these variables and further substantiate the role of Can f 1 in allergic diseases development in this region.

Conclusion

In summary, pre-existing SSIgE responses to common seafood and inhalant allergen sources are associated with elevated specific IgE responses to the dog allergen Can f 1, which in turn is associated with more severe asthma manifestations in the SMCGES population. These findings highlight the importance of molecular-level allergen characterization and integrated management of multi-sensitized individuals in regions with evolving pet exposure patterns.

Declaration of Generative AI and AI-Assisted Technologies in the Writing Process

During the preparation of this work the authors used OpenAI’s ChatGPT (https://openai.com/chatgpt) to improve the manuscript’s readability. After using this service, the authors reviewed and edited the content as needed and took full responsibility for the content of the published article.

Abbreviations

AD, atopic dermatitis; AR, allergic rhinitis; ARIA, Allergic Rhinitis and Its Impact on Asthma; Bla g, Blatella germanica; Blo t, Blomia tropicalis; BSA, Bovine serum albumin; Can f 1, Canis familiaris 1; CI, confidence intervals; Der f, Dermatophagoides farinae; Der p, Dermatophagoides pteronyssinus; Fel d 1, Felis domesticus 1; HDM, House dust mites; IgE, Immunoglobulin E; IQR, interquartile range; ISAAC, International Study of Asthma and Allergies in Childhood; NUS, National University of Singapore; OR, odds ratio; PBS, phosphate-buffered saline; Per a, Periplaneta americana; SMCGES, Singapore/Malaysia Cross-sectional Genetics and Epidemiology Study; SPT, Skin prick test; SSIgE, serum-specific IgE; SU, Sunway University; UTAR, University of Tunku Abdul Rahman; WHO/IUIS, World Health Organization and International Union of Immunological Societies.

Data Sharing Statement

The data underlying this article will be made available from the corresponding author upon reasonable request (FTC).

Ethics Approval and Informed Consent

Participant recruitment study in Singapore was approved by the Institutional Review Board (IRB) in NUS. The study protocol was reviewed and approved by NUS-IRB, approval numbers: 07–023, 09–256, 10–445, 13–075, B-10-343, and H-18-036. Participant recruitment study in UTAR, Malaysia was approved by the UTAR Scientific and Ethical Review Committee (SERC). The study protocol was reviewed and approved by UTAR-SERC, approval number: U/SERC/03/2016. Participant recruitment study in SU, Malaysia was approved by the Research Ethics Committee at SU. The study protocol was reviewed and approved by the Research Ethics Committee at SU, approval number: SUREC 2019/029. All participants provided informed and written consent, with additional written informed consent obtained from the participant’s parent, legal guardian, or next of kin for those below 21 years old. All recruitment procedures were carried out in concordance with the Helsinki Declaration.

Acknowledgment

We thank all participants and their family members for being willing to participate in this study, Dr. Ramani Anantharaman, Dr. Bani Kaur Suri, Parate Pallavi Nilkanth, and Dr. Sri Anusha Matta for help with sample collection.

Funding

Fook Tim Chew (FTC) received grants from the National University of Singapore (N-154-000-038-001 (E-154-00-0017-01); C141-000-077-001 (E-141-00-0096-01)), Singapore Ministry of Education Academic Research Fund (R-154-000-191-112; R-154-000-404-112; R-154-000-553-112; R-154-000-565-112; R-154-000-630-112; R-154-000-A08-592; R-154-000-A27-597; R-154-000-A91-592; R-154-000-A95-592; R-154-000-B99-114), Biomedical Research Council (BMRC) (Singapore) (BMRC/01/1/21/18/077; BMRC/04/1/21/19/315; BMRC/APG2013/108), Singapore Immunology Network (SIgN-06-006; SIgN-08-020), National Medical Research Council (NMRC) (Singapore) (NMRC/1150/2008; OFIRG20nov-0033; MOH-001636 (OFLCG23may-0038, A-8002641-00-00)), National Research Foundation (NRF) (Singapore) (NRF-MP-2020-0004), Singapore Food Agency (SFA) (SFS_RND_SUFP_001_04; W22W3D0006; NRF-SFSRND2SIH-0001; SFS_RND_2_FS_0002), Singapore’s Economic Development Board (EDB) (A-8002576-00-00), and the Agency for Science Technology and Research (A*STAR) (Singapore) (H17/01/a0/008; and APG2013/108). This research is supported by the National Research Foundation Singapore under its Open Fund-Large Collaborative Grant (MOH-001636) (A-8002641-00-00) and administered by the Singapore Ministry of Health’s National Medical Research Council. Kavita Reginald (KR) has received funding from the T20 Research Collaboration Grant Scheme from Sunway University with Grant No.: STR-RMF-T20-005-2019. The funding agencies had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Disclosure

FTC reports grants from the National University of Singapore, Singapore Ministry of Education Academic Research Fund, Singapore Immunology Network, National Medical Research Council (NMRC) (Singapore), Biomedical Research Council (BMRC) (Singapore), National Research Foundation (NRF) (Singapore), Singapore Food Agency (SFA), Singapore’s Economic Development Board (EDB), and the Agency for Science Technology and Research (A*STAR) (Singapore), during the conduct of the study; and consulting fees from Sime Darby Technology Centre; First Resources Ltd; Genting Plantation, Olam International, Musim Mas, and Syngenta Crop Protection, outside the submitted work. The authors declare no other competing interests in this work.

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