# paper.pdf ## Metadata - PDFFormatVersion=1.7 - Language=en - IsLinearized=true - IsAcroFormPresent=false - IsXFAPresent=false - IsCollectionPresent=false - IsSignaturesPresent=false - CreationDate=D:20260611065259+05'30' - Creator=PTC Arbortext Layout Developer 12.1.6202/W-x64 - Custom.EPSprocessor=PStill version 1.84.42 - Custom.WPS-ARTICLEDOI=10.1002/clt2.70181 - Custom.WPS-JOURNALDOI=10.1002/(ISSN)2045-7022 - Custom.WPS-PROCLEVEL=3 - ModDate=D:20260611065722+05'30' - Producer=PDFlib+PDI 9.3.1p6 (C++/Win64) - Title=Temporal Patterns of Allergen Sensitisation in the General Population: The LEAD Study - Trapped=False - pdfuaid:part=1 - xmp:createdate=2026-06-11T06:52:59+05:30 - xmp:creatortool=PTC Arbortext Layout Developer 12.1.6202/W-x64 - xmp:modifydate=2026-06-11T06:57:22+05:30 - xmp:metadatadate=2026-06-11T06:57:22+05:30 - pdf:producer=PDFlib+PDI 9.3.1p6 (C++/Win64) - pdf:trapped=False - pdfx:wps-articledoi=10.1002/clt2.70181 - pdfx:wps-journaldoi=10.1002/(ISSN)2045-7022 - pdfx:wps-proclevel=3 - pdfx:epsprocessor=PStill version 1.84.42 - jav:journal_article_version=VoR - prism:doi=10.1002/clt2.70181 - dc:format=application/pdf - dc:title=Temporal Patterns of Allergen Sensitisation in the General Population: The LEAD Study - xmpmm:documentid=uuid:6a839c17-f927-4079-ae19-163f5b03490d - xmpmm:instanceid=uuid:9bd3e4c3-fd3c-4943-ab2d-051f322cf29d ## Contents ### Page 1 Clinical and Translational Allergy ![Journal Logo]() - ORIGINAL ARTICLE ![Openaccess Logo]() # Temporal Patterns of Allergen Sensitisation in the General Population: The LEAD Study Charmaine J. M. Lim | Abdelrahman Omar | Severin Pötscher | Marie‐Kathrin Breyer | Frits M. E. Franssen | Emiel F. M. Wouters | Robab Breyer‐Kohansal 1Ludwig Boltzmann Institute for Lung Health, Vienna, Austria 2Sigmund Freud Private University, Faculty of Medicine, Vienna, Austria 3Department of Respiratory and Pulmonary Diseases, Clinic Hietzing, Vienna Healthcare Group, Vienna, Austria 4Department of Respiratory and Pulmonary Diseases, Site Penzing of Clinic Ottakring, Vienna Healthcare Group, Vienna, Austria 5NUTRIM, Institute for Nutrition and Translational Research in Metabolism, Maastricht, the Netherlands 6Department of Respiratory Medicine, Maastricht University Medical Center, Maastricht, the Netherlands Correspondence: Charmaine J. M. Lim () Received: 29 December 2025 | Revised: 26 February 2026 | Accepted: 28 May 2026 Keywords: aeroallergens allergic sensitisation atopy cohort studies hypersensitivity skin prick test ## ABSTRACT ### Background: Allergic sensitisation is traditionally viewed as a stable trait despite studies suggesting that it may vary across life‐ course. This study aims to provide longitudinal evidence of allergic sensitisation and its associated factors in the general population. ### Methods: Aeroallergen sensitisation was assessed in the Austrian population‐based cohort using repeated skin prick testing (SPT) across 3 visits (mean visit interval, 4.25 ± 0.33 years). Longitudinal sensitisation patterns were characterised as stable nonsensitised, stable sensitised, new‐onset, resolution or fluctuating. We examined demographic, metabolic, behavioural, environmental and immunological factors across age strata (< 18, 18 ≤ 40, 40 ≤ and ≥ 60 years). ### Results: Among 5046 individuals with follow‐up and valid SPT in all 3 visits, 54.4% remained stably nonsensitised and 30.6% stably sensitised, 5.6% experienced resolution, 4.8% new onset and 4.6% fluctuating sensitisation. New onset expectedly pre-dominated in < 18 years, fluctuation in 18 ≤ 60 years and resolution in ≥ 60 years, indicating that sensitisation is modifiable and time‐varying. Stable sensitisation was strongly associated with parental allergy and blood eosinophils while cumulative smoking modestly reduced its likelihood. Fluctuation was linked to adiposity (in adults ≥ 40 years old) and environmental exposures. Aeroallergen‐specific analysis showed new‐onset sensitisation was driven by outdoor allergens (ragweed, tree pollens and pets) whereas fluctuation was driven by seasonal pollens. ### Conclusion: Although predominantly stable, allergic sensitisation is dynamic and exhibits substantial temporal variation. Resolution and fluctuation occur across all ages and new sensitisation can emerge well into adulthood. These findings challenge the traditional view of fixed sensitisation and suggest it reflects a modifiable phenotype shaped by age and environmental and lifestyle exposures. Emiel F. M. Wouters and Robab Breyer‐Kohansal have contributed equally to this work as last authors. This is an open access article under the terms of the License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2026 The Author(s). Clinical and Translational Allergy published by John Wiley & Sons Ltd on behalf of European Academy of Allergy and Clinical Immunology. Clinical and Translational Allergy, 2026; 16:e70181 ### Page 2 ## 1 | Introduction Sensitisation, the development of allergen‐specific IgE in respo- nse to otherwise benign environmental proteins, underpins allergic disease but often lack symptoms []. It is conventionally identified through a positive skin prick test (SPT) or allergen‐ specific IgE measurement in serum. This approach fails to cap-ture the dynamic nature of sensitisation which may develop, persist, fluctuate, or resolve over time with life‐course evolution poorly understood. Longitudinal evidence of sensitisation patterns of aeroallergens is limited. Birth cohorts show new‐onset sensitisation in child-hood, while older adults studies suggest declining prevalence with age []. Few have examined sensitisation patterns in a single population spanning childhood to late adulthood or assessed how demographic, environmental and immunological factors shape resolution or fluctuation. Likewise, aeroallergen‐ specific patterns and polysensitisation remain poorly charac-terised, despite their clinical relevance. In this study, we mapped skin prick test (SPT) responses to common inhalant indoor and outdoor aeroallergens, aiming to: (i) quantify the proportion of stable, new‐onset, resolving, and fluctuating sensitisation patterns via age‐stratified, population‐ level analyses, (ii) identify total and aeroallergen‐specific pat-terns and (iii) determine associated factors of these trajectories for a lifespan perspective. ## 2 | Methods ### 2.1 | Study Design This study was conducted within the framework of the LEAD (Lung, hEart, sociAl, body) study (clinicalTrials.gov identifier: NCT01727518) which received approval from the local ethics committee of Vienna (Ethikkommission der Stadt Wien; pro-tocol number EK‐11‐117–0711). All procedures in the LEAD study were carried out in accordance with the Declaration of Helsinki, and written informed consent was obtained from all participants and/or legal guardians. The LEAD study is a lon-gitudinal, observational, population‐based cohort study in Austria with follow‐up assessments (2011 to present; mean visit interval, 4.25 ± 0.33 years) []. The study reports longitudinal data from visit at recruitment and 2 further follow‐ups and in-cludes individuals with valid SPT (for both histamine and saline controls) at all visits. All participants aged 6‐82 at recruitment were included in the present study. Our study design involved repeated cross‐sectional assessments of distinct age groups over 3 visits to describe population‐level sensitisation patterns across the lifespan but does not track in-dividual trajectories over decades. Participants were further categorised into five longitudinal sensitisation trajectories based on their patterns of SPT (SPT+, sensitised; and SPT‐, non-sensitised): those with consistently negative sensitisation (stable nonsensitised), consistently positive sensitisation (stable sensi-tised), those who lost sensitisation over time (resolution), those who developed sensitisation later (new‐onset), and those with nonlinear patterns of change (fluctuating). Fluctuating sensi-tised individuals were further divided into SPT‐/SPT+/SPT‐ and SPT+/SPT‐/SPT + subgroups for sensitivity analyses. ### 2.2 | Measurements All participants had withdrawn from antihistamines or gluco-corticoids (oral and cutaneous) for at least 48 h prior to visits and SPT was performed on the participants' forearms by trained technicians. All reported use of antihistamines in this cohort has half‐lives compatible with a 48‐h washout, making sub-stantial residual pharmacologic effect unlikely. SPT was considered positive in the presence of a reaction ≥ 3 mm diameter for at least any one of the following aeroallergens classified as outdoors (ash tree, tree pollen mix [hazel, birch and alder], grass mix [Anthoxantum, Dactylis, Lolium, Phleum andPoa], mugwort, ragweed and ribwort); indoors (mites mix [Dermatophagoides Farinae and Dermatophagoides Pternyssi-nus] and mildew); and pets (dog and cat dander). All partici-pants underwent SPT with an identical panel of aeroallergens obtained from Alk‐Abello for all visits, ensuring consistency in aeroallergen composition and batch quality. Positive (0.1% his-tamine) and negative (0.9% sodium chloride) controls were included in the test panels. Whole‐blood samples were collected from fasted participants (eight‐hours prior to visit) for complete blood cell counts and differential count analysis to obtain measurements for blood eosinophil counts, high‐sensitivity C‐reactive protein (hsCRP), neutrophils and total immunoglobulin E (IgE). IgE measure-ments were reported only for Visits 2 and 3 as IgE was not measured in participants at Visit 1. Height, weight, and waist circumference were measured with a stadiometer and high precision scale for calculations of body mass index (BMI) by weight/height2 and waist‐height ratio. Whole‐body scans were obtained with a Lunar Prodigy (GE Healthcare, USA) Dual x‐ray absorptiometry (DXA) scanner to assess fat mass (FM), and lean mass (LM). Indices of all body composition metrics were addi-tionally calculated as mass/height2. Information on participant's age, smoking status, pack‐years, exposures to dust, passive smoking, socioeconomic status (SES), familial predisposition to allergy, and residence in urban areas or proximal to the main road, was collected by an interview‐ based questionnaire. Annual particulate matter (PM10) and ni-trogen dioxide (NO2) concentrations assigned to residential addresses were estimated with the GRAMM/GRAL model (2015–2021) and were reported only for Visits 1 and 2. Socio-economic status categories were based on a composite score of occupational, educational and income status (SES of partici-pants < 18 years were obtained from their parents or primary guardian) []. Further information of any allergy medication (antihistamines and Leukotriene Receptor Antagonist, LTRA) used; respiratory symptoms such as chronic cough, wheeze, nocturnal symptoms (cough and wheeze) and sinonasal disease (nasal polyps and sinusitis); physician's diagnosis of eczema, rhino‐conjunctivitis and allergy; and history of asthma were self‐reported. ### 2.3 | Statistical Analysis All statistical analyses were performed in R (version 4.3.0; R foundation for Statistical Computing, Vienna, Austria), with the level of significance set at < 5%. Data are presented as mean ± standard deviation or relative frequency (percentage of ### Page 3 group). Analysis of variance (ANOVA) and chi‐squared tests were used for comparisons of nominal and binary variables respectively in between‐group comparisons. T‐tests and Fisher exact tests with false‐discovery rate corrections were applied in post‐hoc analysis. Total and aeroallergen‐specific sensitisation patterns across time were visualised with alluvial plots and heatmaps. To assess for potential effect modification by age, all primary analyses were repeated with stratification by distinct baseline age groups (< 18, 18 ≤ 40, 40 ≤ 60 and ≥ 60 years). Stepwise multinomial multivariable regression models (forced entry and backwards) were used to determine risk factors associated with sensitisation patterns. Among variables, BMI was removed due to collinearity or large missing values (> 10%). Control charts (p‐charts) were used to visualise the proportion of valid histamine and saline controls per monthly batch (x‐axis). The horizontal central line (CL) observed the overall average validity rate across all batches. The upper and lower control limits (UCL and LCL respectively) define the range of variation expected by change based on binomial distribution assumptions. Points highlighted in red points indicate batches flagged as rule violations (i.e., beyond the control limits or part of a nonrandom sequence), suggesting deviations from expected random variations. ## 3 | Results ### 3.1 | Sensitisation at Each Visit and Test Reliability SPT controls were consistently valid across phases (> 98%). Although 8 batches exceeded statistical limits and 40 runs violated run rules, these deviations were rare and isolated (Supporting Information: Figure S1). All histamine and sa-line controls were within acceptable thresholds, supporting minimal batch‐to‐batch variability and ensured that the observed changes in sensitisation patterns reflected biological rather than technical variation. Among 5046 eligible participants (48.3% males; mean age 46.2 ± 17.6 years; and 19.1% current smoking), sensitised in-dividuals were more often males had lower fat mass index (FMI) and higher lean mass index (LMI), fewer current smokers and lower pack years, and reported higher parental allergies (Table). Eosinophils and IgE were significantly higher in the sensitised groups at Visits 2 and 3 (p < 0.001). Lifestyle and environmental differences were minimal. In sensitised in-dividuals, body composition and smoking exposures increased with age (Table). SPT positivity fluctuated across visits with moderate reproduc-ibility (Fleiss' κ 0.741–0.798; Figure) and minimal net change (−0.01%; Cohen's H, −0.02, McNemar's p = 0.106). Outdoor al-lergens were generally stable although ragweed (Fleiss' κ 0.471–0.523) and ribwort (Fleiss' κ 0.522–0.624) were more vari-able. Grass pollen was most consistent (Fleiss' κ 0.715–0.838) and most prevalent (> 50% across ages) with strong seasonal peaks (spring/summer) (Figure). Mite sensitisation declined, whereas mold remained low and stable. Pet sensitisation increased in< 18 years but decreased in 18 ≤ 40 years, with cat sensitisation consistently higher than dog (Figure). ### 3.2 | Longitudinal Sensitisation Patterns and Associated Factors The distribution of longitudinal sensitisation patterns within each age strata is visualised in Figure and Supporting Information: Tables S1–S4. Stable SPT−increased with age (65.9% in ≥ 60 vs. 50.3% in < 18 years), while stable SPT + peaked in 18 ≤ 40 years (34.7%). New‐onset was most common in < 18 years (8.9%), while resolution was constant across ages (7.0%–8.2%). Fluctuating sensitisation ranged 4%–8% across strata, peaking in 40 ≤ 60 years (8.3%). Sensitive analysis using latent class analysis (LCA), performed using SPT positivity at 3 visits as indicators, supported a 2‐class solution corre-sponding to stable positive and stable negative sensitisation in all age‐stratified groups. Models with more classes up to 5 fit worse (Bayesian Information Criterion 12522.1 vs. 12624.5) and aligned poorly with predefined patterns (weighted κ −0.2 to−0.143), indicating resolution, new‐onset and fluctuation were infrequent relative to persistence (Supporting Information: Table S5). In < 18 years, stable SPT + occurs more often in males (55.0%), with higher eosinophils, asthma (8.6%) and parental allergies (69.9%). In 40 ≤ 60 years, stable SPT + remained eosinophilic and asthma‐associated; resolution, new‐onset and fluctuations groups were more prominent among women and associated with higher smoking and FMI. In ≥ 60 years, resolution and fluctuating were linked with smoking and higher adiposity whereas persistent sensitisation remained eosinophilic. Stable SPT‐individuals showed higher smoking and BMI from early adulthood. Body composition also differed for all age strata: stable SPT + had the lowest BMI and FMI, whereas the fluc-tuating group had the highest BMI and FMI although no clear subgroup explanation (SPT+/SPT‐/SPT + vs. SPT‐/SPT+/SPT‐) accounting for these body composition differences (Supporting Information: Table S6). Within the fluctuation group, low overall positivity with batch‐to‐batch variability was observed with excellent control performance (Supporting Information: Figure S2). Allergen‐specific sub‐analyses of the fluctuation group (Supporting Information: Figure S3) indicated that fluctuation disproportionately involved seasonal allergens such as ragweed, ribwort, and tree pollens, whereas perennial aller-gens such as grass and mites were largely stable. Allergy medication use was generally highest in the stable SPT+ (~10% of participants < 40 years) and fluctuating groups, with the exception observed in those 40 ≤ 60 years where stable SPT+and new‐onset predominated. Sensitised groups also reported more allergy, rhino‐conjunctivitis and eczema whereas wheeze and chronic cough were less discriminative between SPT patterns. Multinomial stepwise regression (Table) showed strong asso-ciations of parental allergies and eosinophils with stable SPT + across ages, notably in 18 ≤ 40 years (corresponding OR [95% CI]: 3.00 [2.25, 4.00] and 1.00 [1.00, 1.00], p < 0.001) and in 40 ≤ 60 years, although in this group smoking exposure reduced the likelihood of stable SPT+ (pack‐years, OR 0.99 [95% CI 0.98, 0.99], p < 0.001). In ≥ 60 years, cumulative smoking similarly attenuated stable SPT+ (OR 0.99 [95% CI 0.98, 1.00], p = 0.050). Fluctuating sensitisation showed age‐specific associations: resi-dence near a main road (OR 2.27 [95% CI 1.13, 4.54], p = 0.021) in ### Page 4 ### Page 5 ### Page 6 ### Page 7 18 ≤ 40 years; waist–to‐height ratio and PM10 (corresponding OR [95% CI]: 66.5 [7.79, 566.78] and 1.21 [1.08, 1.36], p ≤ 0.001) in 40≤ 60 years; and NO2 (OR 1.06 [95% CI 1.01, 1.12], p = 0.029) in≥ 60 years. Resolution showed weaker associations overall except hsCRP in ≥ 60 years (OR 1.68 [95% CI 1.02, 1.12], p = 0.009). In sensitivity analyses, smoking status showed small inverse asso-ciations with stable SPT+ (Supporting Information: Table S7). No temporal interactions were observed. ### 3.3 | Allergen‐Specific Patterns and Polysensitisation Among those sensitised at baseline, 59.2% developed ≥ 1 addi-tional sensitisation during follow‐up. The probability of acquiring new sensitisations differed significantly according to the type of primary sensitisation (p < 0.001). Participants initially sensitised to outdoor allergens showed the highest likelihood of developing additional sensitisations (62.3%), compared with pet (56.4%) and indoor allergens (50.9%). In pairwise comparisons, outdoor sensitisation was associated with higher odds of sensitisation expansion compared with indoor (OR 1.60 [95% CI 1.36, 1.88]) and pet sensitisation (OR 1.25 [95% CI 1.03, 1.52]). Stable sensitisation was most frequent for seasonal allergens such as grass (> 51.3% of sensitised adults). Early tree pollen mix was common in younger adults but resolved increasingly with age (≥ 60 years; Figures and). Ragweed and ribwort sensitisation were most variable, contributing disproportionately to the fluc-tuating group and ragweed new‐onset sensitisation peaked in adolescents (< 18 years; up to 34%). Mite sensitisation declined across ages while mold remained rare and stable. Cat sensitisation increased progressively in younger adults; dog sensitisation resolved in older adults (up to 56% resolution in ≥ 60 years). Overall, fluctuation was uncommon (< 5% per allergen)< 18 years more often developed ragweed (up to 34%) and early tree pollens sensitisation; ≥ 60 years showed higher resolution (dog, 56% and mold, 36%; Figure) 40 ≤ 60 years had highest stable sensitisation to grass and mites (> 50%). Polysensitisation patterns mirrored these trends (Supporting Information: Table S8): stable SPT− participants had no al-lergens; stable SPT + averaged 2 allergens across visits; and fluctuating individuals had the highest counts (mean 3–4 al-lergens) and observed greatest variability. New‐onset mono-sensitisation was more frequent in younger ages (19% increase in allergens in < 18 years vs. 5% in ≥ 60 years), while resolution predominated in older adults. Those with resolution showed declining allergen numbers over time (> 1 allergens in Visit 1 vs. 0 in Visit 3). ## 4 | Discussion Our study offers the first longitudinal population‐based, life‐ course perspective on aeroallergen sensitisation across a broad age stratum (6‐82 at baseline) and showed that sensitisation ![Image of FIGURE 1]() ### Page 8 patterns are far more dynamic than traditionally assumed. Although overall SPT positivity remained stable (~35–40%), in-dividual patterns showed marked heterogeneity. While prior literature has framed sensitisation as a largely fixed trait once established [], we demonstrate clear evidence of new‐onset, resolution and fluctuating patterns across the lifespan > 15% of participants transitioned between sensitised and nonsensitised status, and these transitions were strongly age dependent. New‐ onset predominated in < 18 years, fluctuation in midlife and resolution in older adults, extending prior child‐ or adult‐ focused findings []. We show that age was the primary determinant of sensitisation patterns, aligned with previous reports of declining new‐onset sensitisation with age []. Stable sensitisation was most common in young adults, particularly ragweed and tree pollens, whereas older adults were more likely to be stably nonsensitised or experience resolution. Polysensitisation further showed that stable sensitised participants typically carried approximately two allergens, whereas the fluctuating group bore the heaviest burden, averaging three to four allergens over time across age groups. This is consistent with prior work linking poly-sensitisation by molecular analysis of specific IgE to more severe and unstable allergic phenotypes []. Patients sensitised to> 3 allergens have been reported with more severe rhinitis symptoms (19%) compared to nonsensitised or mono‐/dual‐ sensitised individuals (8%–12%) []. Additionally, resolution always observed loss of polysensitisation whereas new‐onset was generally monosensitisation. While resolution was most frequently observed in older adults, reduced dermal mast cell function and skin thinning with age may blunt SPT responses, potentially mimicking true desensitisation []. Nevertheless, the overall pattern remains striking across all age groups: new‐onset sensitisation was predominantly driven by outdoor allergens, particularly ragweed, and pet dander. Our allergen‐specific analysis further revealed that among in-dividuals already sensitised at baseline, 59% developed at least one additional sensitisation during follow‐up with participants initially sensitised to outdoor sensitisations having the highest likelihood of sensitisation expansion (62.3%), followed by pet (56.4%) and indoor (50.9%) sensitisations. These findings may also reflect that outdoor allergen exposure may drive poly-sensitisation across the life course. Overall, these SPT patterns aligns with ecological observations linking increasing ragweed spread and pet ownership trends to sensitisation dynamics in European populations [], suggesting that continued or renewed environmental exposure, and not solely predisposition, contributes to the development of new sensitisation later in life. Risk factor profiles differed substantially by age. Across all age groups, parental allergy emerged as a robust associated factor of both stable and new‐onset sensitisation. Among participants aged < 18 years, classical atopic markers including male sex, parental allergy, and higher eosinophils, predominated. In adults, behavioural and metabolic factors were influential: cu-mulative smoking exposure was associated with stable or reso-lution patterns, and lower adiposity appeared protective, ![Image of FIGURE 2]() ### Page 9 contrasting with literature linking obesity to asthma/allergy risk []. This likely reflects differences between short‐term symp-tom outcomes in prior studies and the life‐course pattern approach used here. This finding was robust, as lower adiposity was also observed in sensitised individuals in cross‐sectional analysis. This may relate to body fat distribution rather than total adiposity: visceral fat drives Th1/Th17 inflammation [] potentially suppressing Th2‐mediated allergic re-sponses, consistent with discordant BMI‐atopy associations re-ported previously []. In our longitudinal analysis, current and former smokers had lower odds of stable sensitisation, and higher cumulative to-bacco exposure was modestly associated with reduced likeli-hood of persistent sensitisation over time. These findings suggest that smoking may attenuate the persistence of allergic sensitisation rather than prevent its development or promote resolution. This is consistent with mixed evidence: while many cross‐sectional studies report higher total IgE among current smokers [], longitudinal studies suggest a reduced inci-dence of new sensitisation among sustained smokers []. This may reflects dual pro‐inflammatory and immunosuppres-sive effects of tobacco, which can alter antigen presentation and Th1/Th2 balance []. Hence, the net effects on sensitisation may vary by context and allergen. Moreover, total IgE measures may not reflect local cutaneous responses measured by SPT, particularly for aeroallergens []. Overall, our results sup-port a modest but directionally consistent influence on sensitisation trajectories. Further studies on sustained versus changing smoking status, allergen class and smoking exposures are required to determine if this observation reflects a true immunologic effect or residual confounding. The mismatch between sensitisation, clinical manifestations and use of allergy medication is most notable. Despite clear differ-ences in allergic outcomes across sensitisation patterns, overall use of allergy medication was modest and particularly low in participants < 40 years, where only approximately 10% reported taking antihistamines or leukotriene receptor antagonists. The gap is consistent with previous reports that many sensitised in-dividuals, especially adolescents and young adults, either tolerate symptoms, self‐manage without regular pharmacotherapy or remain undiagnosed in primary care []. Discrepancies be-tween sensitisation and clinical symptoms may also be influenced by the use of preventive measures such as allergen avoidance or environmental control [] Low medication use, particularly in the context of fluctuating and resolving sensitisation, may also partly reflect intermittent or mild symptom profiles typically observed in population‐based cohorts []. While our study did not directly compare symptomatic outcomes between poly‐ and monosensitisation, our findings align with prior literature suggesting that symptomatic allergies are more prevalent in in-dividuals with poly‐sensitisation. Asymptomatic sensitisation has been observed to be more common in younger individuals with mono‐sensitisation and less frequent family history [], reflecting the cumulative effect of multiple allergen exposures ![Image of FIGURE 3]() ### Page 10 ### Page 11 over time that could contribute to the development of clinical symptoms in polysensitisation. Future integrating detailed symptom data with longitudinal sensitisation patterns could further elucidate these relationships. A novel contribution of our study is the identification of a distinct group with fluctuating sensitisation. While this group comprised only 4%–8% of the population, it carried the heaviest allergen burden, had higher adiposity and smoking exposures. Unlike stable sensitisation, which was strongly associated with parental allergy and eosinophils, fluctuation was linked to metabolic, inflammatory, and environmental factors. We lacked quantitative wheal size data and therefore could not formally separate borderline SPT reactions from unequivocal positives in the fluctuation group. Nonetheless, allergen‐specific analyses showed that fluctuation was especially common for seasonal allergens (ragweed, ribwort, tree pollens) and aligned with their respective pollen seasons, especially in adolescents and in young adults. This seasonal and allergen‐specific supports an inter-pretation that environmental exposure, rather than technical variability alone, contributes to the observed fluctuations. While we cannot exclude that some fluctuations reflect borderline reactivity, the strong alignment with seasonal pollen exposure suggests that at least part of this pattern represent genuine temporal variation in sensitisation. This aligns with recent molecular IgE‐profiling in the LEAD cohort, demonstrating that profiling at the individual allergen level can unmask heteroge-neity in sensitisation even in adult asthma patients []. This prior study, however, is cross‐sectional and may not directly reflect temporal fluctuations, while the longitudinal SPT find-ings here demonstrate dynamic changes in sensitisation pat-terns over time, particularly for seasonal allergens such as ragweed and tree pollens. Beyond overall temporal trends, qualitative shifts in specific allergen groups may reflect environmental and lifestyle changes. The decline in house dust mite sensitisation may indicate im-provements in housing quality, indoor ventilation and humidity control over recent decades, consistent with European popula-tion trends showing declining mite exposure alongside better insulation and air quality control []. In contrast, decreased animal sensitisation likely reflects increased pet ownership in Austria while the growing prevalence and fluctuation of pollen sensitisation likely results from increasing pollen loads, extended flowering seasons or northward spread driven by climate change, urbanisation and land‐use changes [ ![Image of FIGURE 4]() ### Page 12 ]. Grass pollen notably exhibited a gradual rise before reaching plateauing, while trends for other aeroallergens varied by region and year. Other contributors include environmental exposures, including pollutants such as diesel exhaust carbon particles (which are known to bind to major allergen such as Lol p1 in in vitro conditions []) [], and geographical location []; hormonal shifts, intercurrent illnesses, metabolic changes, diet and activity []; and aging‐related changes in skin and immune function []. In summary these findings suggest that fluctuation sensitisation is shaped by environmental and systemic factors rather than by classical atopy. Clinically, fluctuating polysensitisation may contribute to variable or seasonal symptoms, often linked to more severe allergic disease and intermittent rhinitis or asthma not captured by single cross‐sectional assessments. Recognition of fluctuation as a standalone phenotype highlights the impor-tance of repeated testing and consideration of tailored in-terventions, including allergen immunotherapy or exposure‐ reduction strategies. Strengths of this study includes a comprehensive assessment of factors influencing aeroallergen sensitisation in a large, population‐based cohort with repeated and standardised SPT measurements over 12 years and with a broad age stratum. This design enabled us to characterise resolution and fluctuations, which are rarely reported in the literature. Importantly, the study integrated immunological markers, parental allergy his-tory, lifestyle factors including detailed body composition and smoking, and environmental exposures, providing a multidi-mensional view of associated factors of sensitisation patterns across the life course. Several limitations merit consideration. First, while our 8–12‐year follow‐up reveals age‐dependent sensitisation patterns, individual transitions between age strata were not captured within this timeframe. Second, sensitisation was assessed by SPT only; allergen‐specific IgE was not available for all participants which could have provided complementary information on sensitisation intensity and mechanisms. Third, although we captured several host, metabolic, and environ-mental risk factors, data on key contributors to sensitisation dynamics, such as hormonal changes, illness history, diet, and detailed pollutant exposure, were not available, limiting our ability to fully characterise the drivers of fluctuation and reso-lution. Fourth, as the cohort is Austrian and largely European, results may not generalise to populations with different genetic backgrounds, allergen exposures or lifestyles. Finally, our find-ings should be interpreted in consideration of several method-ological limitations. Although SPT visits were not standardised to a specific season or month, the distribution of visit timing across the three assessments was comparable, reducing the likelihood of seasonal bias. Additionally, no explicit restrictions were placed on alcohol intake or vigorous exercise, which can transiently influence skin perfusion. While batch‐to‐batch variability in allergen vials cannot be entirely excluded, our control charts demonstrated > 98% validity for histamine/ saline controls suggesting minimal technical bias, and operator consistency was maintained through trained technicians. Future studies involving SPT could use automated SPT devices to further standardise testing []. ## 5 | Conclusion In conclusion, our study demonstrates that allergic sensitisation is a dynamic trait rather than a fixed lifelong characteristic. Resolution and fluctuation occurred across the life course, and new‐onset sensitisation can develop well into adolescence and adulthood. These findings challenge long‐standing assumptions in allergy studies and highlight the importance of longitudinal monitoring. Recognising these patterns can guide age‐ and risk‐ specific approaches aimed at preventing the progression to persistent allergic disease. ## Author Contributions All authors have read and given their final approval for this version to be published. C.J.M.L was involved in the conceptualisation, methodology, formal analysis, interpretation of the data and the writing and editing of the manuscript. A.O. was involved in the formal analysis and inter-pretation of the data in the manuscript. S.P. was involved in the final review of the manuscript. R.B.‐K., M.‐K.B., F.M.E.F., E.F.M.W. were involved in supervision, and the final review and editing of the manuscript. ## Acknowledgments All authors sincerely thank all participants for their willingness to contribute to this study. We would also like to acknowledge Michael Sturm and the staff of the LEAD study, Austria, for their support with recruiting and managing participants so that high quality data is ob-tained. We would also like to thank Ms. Barbara Wögerbauer for her administrative support. ## Funding The Austrian LEAD Study Austrian LEAD study has unrestricted financial support from the Ludwig Boltzmann Gesellschaft, Sigmund Freud Private University Faculty of Medicine, Vienna Healthcare Group, the Lower Austrian Health and Social Fund, AstraZeneca, Chiesi Farmaceutici, GlaxoSmithKline, and Menarini Pharma. None of the supporting parties has any participation in the data, nor have they contributed to the design or the content of the manuscript. ## Ethics Statement The study was conducted within the framework of the LEAD study which has been approved by the local Ethics committee of Vienna (EK‐11‐117–0711) with the project identification code, NCT017257518 (ClinicalTrials.gov) and in accordance with the Declaration of Helsinki. ## Conflicts of Interest The authors declare no conflicts of interest. R.B.‐K. and M.‐K.B. reports consulting fees from AstraZeneca, Menarini, Sanofi, Boehringer Ingel-heim, Novartis Pharma, GSK and Sanofi for advisory board members outside the submitted work. F.M.E.F. reports consulting fees from MSD and Sanofi and honoraria from AstraZeneca, Chiesi, GSK, Sanofi and Pfizer outside of the submitted work. C.J.M.L, A.O., S.P., E.F.M.W. have nothing to disclose. ## Data Availability Statement Data relevant to this study can be made available upon request to the corresponding author. ### Page 13 ## References - 1. R. van Ree, L. Hummelshøj, M. Plantinga, L. K. Poulsen, and E.Swindle, “Allergic Sensitization: Host‐Immune Factors,” Clinical andTranslational Allergy 4, no. 1 (2014): 12,. - 2. J. Batlles‐Garrido, J. Torres‐Borrego, T. Rubí‐Ruiz, et al., “Prevalenceand Factors Linked to Allergic Rhinitis in 10 and 11‐Year‐old Childrenin Almería. Isaac Phase II, Spain,” Allergologia et Immunopathologia 38,no. 3 (2010): 135–141,. - 3. V. Garcia‐Larsen, J. F. 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