Contemporary allergy practice is increasingly challenged by the misinterpretation of IgE sensitisation profiles, cross-reactive IgE binding and irritant-induced symptoms. With the expanding availability of component-resolved diagnostics (CRD), clinicians now receive highly granular molecular reports that enhance specificity but may paradoxically increase diagnostic confusion when interpreted without a structured immunologic framework 1, 2. Misclassification of triggers remains a major driver of overdiagnosis, unnecessary dietary or environmental restriction and inappropriate therapeutic decisions. Reproducibility of symptoms following exposure remains a critical criterion for defining clinical allergy and distinguishing it from incidental sensitisation or transient irritant responses. The World Allergy Organisation defines allergy as an abnormal, reproducible, immune-mediated response to an external antigen. In clinical practice, diagnostic confusion frequently arises when these defining attributes—abnormality, reproducibility, antigen specificity and immune mediation—are not systematically considered. A structured mechanistic framework that explicitly distinguishes immune from nonimmune mechanisms and clinically relevant from incidental sensitisation may therefore enhance diagnostic precision. Two common clinical scenarios illustrate the problem. A child sensitised to birch pollen demonstrates low-level IgE to peanut Ara h 8 and is labelled ‘peanut allergic’ despite regular tolerance to peanut ingestion. Conversely, an adolescent with recurrent wheeze during high-pollution days undergoes extensive IgE testing and is diagnosed with ‘multiple allergies’ despite the absence of clear sensitisation. In both instances, the absence of a mechanistic differentiation between primary sensitisation, cross-reactivity and irritant exposure leads to diagnostic ambiguity. Using these criteria, environmental and food-related triggers can be categorised into four mechanistically distinct groups: primary allergens, cross-reactive allergens, irritants and adjuvant factors (Figure 1). Primary allergens are capable of initiating de novo IgE production in a previously nonsensitised host. These molecules drive Th2 polarisation, promote IL-4/IL-13–mediated class switching and establish immunologic memory 3. They fulfil all three criteria: induction of IgE, IgE binding and symptom generation. Examples include major house dust mite proteases such as Der p 1, birch pollen allergen Bet v 1, and stable seed storage proteins such as Ara h 2. Identification of the primary sensitising molecule is central to rational allergen-specific immunotherapy selection and preventive strategies 4. Failure to identify the true primary allergen may result in targeting secondary molecules with limited therapeutic value. Cross-reactive allergens share structural homology with primary allergens and bind pre-existing IgE but do not independently initiate primary sensitisation. Typical examples include PR-10 proteins, profilins and cross-reactive carbohydrate determinants (CCDs) 5, 6. In pollen-sensitised individuals, homologous proteins in apple, hazelnut or soy may bind IgE generated against the primary pollen allergen. However, IgE binding does not uniformly translate into clinically significant reactions. Many patients demonstrate molecular sensitisation without systemic symptoms. These triggers satisfy criterion (2), may variably satisfy criterion (3), but do not meet criterion (1). Failure to recognise this distinction contributes to unnecessary food avoidance, nutritional compromise and anxiety—particularly in children and their parents or caregivers who are responsible for daily dietary and safety decisions. Sensitisation represents immunologic recognition; allergy represents clinically relevant reactivity. CRD offers the opportunity to distinguish these entities, but only if interpreted mechanistically rather than numerically. Irritant exposures induce symptoms without IgE involvement. Air pollutants, particulate matter, sulfur dioxide, tobacco smoke and volatile chemicals can provoke cough, wheeze or rhinitis through epithelial injury, oxidative stress and neurogenic inflammation 7. These triggers satisfy only criterion (3). They neither induce specific IgE nor bind allergen-specific IgE. In many rapidly urbanising regions of the Asia-Pacific, pollution-related respiratory symptoms are frequently misattributed to ‘allergy’ 8, leading to inappropriate testing and misclassification. Distinguishing irritant-mediated inflammation from IgE-driven disease is essential for rational management, as therapeutic strategies differ fundamentally. While allergic inflammation may respond to allergen avoidance or immunotherapy, irritant-driven symptoms require exposure mitigation and control of airway inflammation rather than allergen targeting. Certain environmental exposures do not directly bind IgE but enhance allergic sensitisation or amplify inflammatory responses. Diesel exhaust particles (DEP) are well-described adjuvants that promote Th2 skewing and increase IgE production to co-exposed allergens 8. These agents may disrupt epithelial barrier integrity, increase antigen presentation and amplify cytokine responses. Unlike primary allergens, adjuvant factors do not independently initiate allergen-specific IgE responses to themselves. Unlike irritants, their role extends beyond symptom induction to modification of the sensitisation process itself. They may influence disease severity, epidemiology and possibly long-term outcomes. In highly polluted settings, their interaction with aeroallergens may partially explain increasing allergy prevalence and severity. Recognition of adjuvants is particularly relevant in the Asia-Pacific context, where environmental transitions and urban exposures are rapidly evolving. These agents are not allergens per se but modify the allergic landscape. Importantly, sensitisation does not equate to allergy. Clinical correlation remains indispensable 6, 9. A mechanistic classification may enhance diagnostic precision without increasing diagnostic complexity (Figure 1). A structured differentiation model may improve allergy education, rational use of CRD panels, patient communication, and public health messaging—particularly in regions where broad allergen panels are increasingly used without standardised interpretative approaches. By shifting focus from ‘positive tests’ to ‘immunologic behaviour’, clinicians may reduce overdiagnosis and promote patient-centred care. This framework is conceptual and intended to aid clinical interpretation rather than replace established diagnostic algorithms. Further discussion and validation across diverse populations may strengthen its applicability. Importantly, this framework explicitly distinguishes immune-mediated allergic responses from nonimmune irritant mechanisms, aligning diagnostic reasoning with the formal immunologic definition of allergy. Distinguishing primary sensitisation, cross-reactive IgE binding, irritant-induced symptoms and adjuvant effects is essential for rational allergy diagnosis. A simple three-criterion immunologic framework offers conceptual clarity in the molecular diagnostic era. By aligning diagnostic interpretation with immunologic function, clinicians may reduce misclassification, avoid unnecessary interventions and improve therapeutic precision in contemporary allergy practice. N.G. and S.A.N. have conceptualised the initial draft, searched the literature and approved the final version after necessary editing. Both are accountable for all aspects of the work. The authors have nothing to report. The authors have nothing to report. The authors declare no conflicts of interest. The authors have nothing to report.
Gupta et al. (Wed,) studied this question.
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