Type 2 Mechanisms in Pediatric Allergic Diseases

Type 2 inflammation is a central mechanism across pediatric allergic diseases, including atopic dermatitis, food allergy, eosinophilic esophagitis, allergic rhinitis and asthma. Driven by epithelial barrier dysfunction, alarmin release, Th2 and ILC2 activation, and eosinophilic inflammation, type 2 pathways shape early sensitization and chronic disease. This mini-review summarizes current evidence on cellular and molecular mechanisms in childhood, integrating barrier biology, neuroimmune interactions and endotyping, and discusses therapeutic implications of targeted biologics.

INTRODUCTION

The burden of pediatric allergic diseases continues to rise globally, which is driven by environmental changes, microbial dysbiosis, and lifestyle factors ¹. Despite their clinically diverse phenotypes, disorders such as atopic dermatitis (AD), food allergy, eosinophilic esophagitis (EoE), allergic rhinitis, and asthma share a common immunological hallmark: type 2 (T2) inflammation. This inflammatory axis is orchestrated by epithelial-immune interactions involving alarmins, Th2 cells, innate lymphoid cells type 2 (ILC2), eosinophils, mast cells, and B cells ². In children, these processes are strongly influenced by developmental immunology, making early life a critical period during which sensitization and immune polarization may shape long-term atopic trajectories.

This review summarizes the current evidence on key molecular and cellular pathways underlying T2 immunity in childhood, examining their implications across major pediatric allergic diseases and highlighting therapeutic advancements.

MOLECULAR AND CELLULAR MECHANISMS OF TYPE 2 IMMUNITY IN CHILDREN

T2 immunity in childhood arises from the interplay between epithelial barriers, innate and adaptive immune cells, the microbiome, and neuroimmune circuits. Although traditionally associated with airway diseases, T2 mechanisms are now recognized as shared drivers across skin, gut and respiratory organs, reflecting a unified pathogenic framework.

Across the three major barrier organs implicated in pediatric allergic diseases – namely the skin, intestinal mucosa and respiratory epithelium – similar structural and immunologic principles govern the initiation of T2 responses ³. These tissues share parallel epithelial features, including tight and adherens junctions, mucus layers, microbial interfaces and resident immune sentinels. When these structures are impaired, each barrier becomes permissive to allergen penetration, microbial dysbiosis and exaggerated immune activation. In the skin, defects in filaggrin, loricrin, claudins and ceramides compromise the stratum corneum, allowing allergens and microbes to penetrate and stimulating keratinocytes to release TSLP, IL-25 and IL-33, which then initiate Th2- and ILC2-mediated inflammation. Similarly, in the gastrointestinal tract – including both intestinal mucosa and the esophageal epithelium of children with food allergy or EoE – damage to the mucus layer, disruption of tight junctions and microbiome alterations increase antigen permeability, and enterocytes and esophageal epithelial cells respond to this heightened exposure by releasing the same alarmins that drive T2 responses. In the airways, exposure to pollutants, viral infections and aeroallergens induces epithelial stress, leading to alarmin secretion, mucociliary dysfunction and subsequent amplification of the T2 inflammatory axis. Together, these parallel mechanisms across skin, gut and airway barriers explain why children with early, severe AD are at increased risk of developing food allergy, EoE and asthma, reflecting a unified barrier – alarmin – T2 axis that operates across organ systems during critical windows of immune development ³.

ILC2s are crucial innate amplifiers across all barrier organs. They respond rapidly to epithelial alarmins by producing IL-5 and IL-13, contributing to eosinophilic inflammation in lesional skin, promoting esophageal and intestinal eosinophilia in EoE and food allergy, and sustaining non-atopic eosinophilic asthma in younger children, where adaptive Th2 immunity is less dominant. Adaptive Th2 cells then orchestrate chronic T2 inflammation through IL-4, IL-5, IL-9 and IL-13 secretion. In the skin, IL-4 and IL-13 directly impair keratinocyte differentiation, depress antimicrobial peptide production and perpetuate barrier breakdown; in the gastrointestinal tract they modulate permeability, smooth muscle tone, and fibroblast activation; in the airways they promote mucus hypersecretion, smooth-muscle proliferation and allergen-specific IgE production. B cells undergo IgE class switching under IL-4/IL-13 signaling in all these tissues, reinforcing allergen-specific inflammation systemically ⁴.

Eosinophils represent a unifying effector population across T2 diseases. In AD they contribute to chronic dermal inflammation and remodeling; in EoE they dominate the tissue infiltrate and drive epithelial injury and fibrosis; and in asthma they modulate airway hyper-responsiveness and risk of exacerbation, with pediatric data indicating reduced antiviral responsiveness in severe forms. The IL-5 axis governs eosinophil recruitment, activation and survival across all barrier tissues ^3,4.

The pediatric T2 immune response is also tightly linked to sensory neuronal pathways. In the skin, IL-4, IL-13 and IL-31 directly activate pruriceptors, causing intense itch and promoting scratching, which in turn induces further epithelial damage and alarmin release. In the airways, T2 cytokines modulate vagal afferents, enhancing cough reflex sensitivity, bronchoconstriction and mucus secretion. In the gut, neuronal-immune communication influences motility, visceral hypersensitivity and epithelial permeability, although the mechanisms in children are less clearly defined than in skin and airways. These neuroimmune circuits help explain why IL-5 blockade improves eosinophilia but not itch, whereas IL-4Rα blockade can ameliorate both inflammatory and sensory symptoms ⁵.

Finally, early-life microbiome alterations across skin, gut, and airways prime the developing immune system toward T2 responses. Skin dysbiosis with Staphylococcus aureus overgrowth in infants with AD, reduced short-chain fatty acid-producing bacteria in the gut of children who later develop food allergy or asthma, and airway colonization by potentially pathogenic genera such as Moraxella and Haemophilus have all been associated with increased T2 susceptibility. The skin-gut-lung microbiome axis therefore mirrors the barrier axis and reinforces systemic T2 risk ^3,4.

TYPE 2 MECHANISMS IN SPECIFIC PEDIATRIC ALLERGIC DISEASES

T2-driven mechanisms across major pediatric allergic diseases are summarized in Table I, which highlights shared and organ-specific pathogenic pathways involving epithelial barrier dysfunction, alarmin release, Th2 and ILC2 activation, eosinophilic inflammation and neuroimmune modulation.

THERAPEUTIC IMPLICATIONS: TARGETED BIOLOGICS IN PEDIATRIC TYPE 2 DISEASE

The growing understanding of T2 mechanisms in childhood has led to a rapid expansion of targeted biologic therapies, which are now an essential component of care for selected pediatric patients with moderate-to-severe disease. By acting on key cytokines and receptors within the T2 pathway, biologics offer organ-specific and, in many cases, multi-organ benefits, reflecting the systemic nature of T2 inflammation ⁶.

Anti-IgE therapy (omalizumab) was the first biologic approved for pediatric allergic asthma and has demonstrated efficacy in reducing exacerbations, improving symptom control, and lowering corticosteroid burden. Its mechanism – neutralization of circulating IgE and downregulation of FcεRI receptors on mast cells and basophils – makes it particularly effective in children with allergic sensitization and evidence of IgE-driven disease ⁶.

Anti-IL-5 and anti-IL-5R agents (mepolizumab, benralizumab) specifically target eosinophilic inflammation, a hallmark of severe pediatric asthma. Clinical studies in children have shown reductions in exacerbations, improvements in lung function and durable decreases in blood and airway eosinophils, with mepolizumab now approved from age ≥ 6 years in many regions. These therapies are particularly valuable in patients with recurrent exacerbations, high eosinophil counts, and poor response to high-dose inhaled corticosteroids ^6,7.

Anti-IL-4Rα therapy (dupilumab) has transformed the management of pediatric T2 diseases by blocking IL-4 and IL-13 signaling, the central cytokine hub orchestrating T2 inflammation across skin, gut and airways. Dupilumab is now approved for children with moderate-to-severe AD, eosinophilic asthma, and EoE, with consistent improvements observed across all indications, including reductions in itch, eczema severity, asthma exacerbations, airway eosinophilia and esophageal inflammation. Pediatric trials demonstrate rapid onset of action, favorable safety and significant improvements in quality of life ^7,8. The availability of a single biologic targeting multiple organ systems reinforces the concept of a unified T2 endotype and offers clinicians an opportunity to treat multimorbidity with a single intervention ⁸.

Anti-TSLP therapy (tezepelumab) represents a shift toward targeting upstream epithelial alarmins rather than downstream cytokines. By inhibiting TSLP – an early epithelial alarm signal involved in activating dendritic cells, Th2 cells, ILC2 and mast cells – tezepelumab offers broad suppression of T2 pathways, including both IgE-mediated and non-IgE eosinophilic inflammation. Although pediatric data are still emerging, early studies suggest potential benefit across heterogeneous asthma endotypes, including children with mixed granulocytic or paucigranulocytic patterns ⁷.

Emerging therapies include anti-IL-33 and anti-ST2 agents, anti-IL-25 blockade, JAK inhibitors for severe AD and targeted modulators of epithelial barrier repair. These approaches reflect a shift toward intervening earlier in the inflammatory cascade, with the potential to modify disease progression rather than merely suppress symptoms. Given the systemic nature of T2 inflammation, it is plausible that future biologics will be developed not for a single organ-specific disease, but for broader “multi-organ T2 disease phenotypes” in children ⁷.

From a clinical perspective, biologic selection in pediatrics increasingly relies on a combination of endotype-driven markers (eosinophils, FeNO, IgE levels, sensitization patterns), disease severity, age of onset, and the presence of multiorgan involvement or barrier dysfunction. Importantly, successful treatment of one T2 disease often yields improvements in others – for example, dupilumab improves both AD and asthma, and may attenuate progression along the atopic march. Thus, targeted biologics not only address the symptoms of severe disease, but increasingly offer a strategy to modify long-term disease trajectories in high-risk children.

These therapeutic advances set the stage for the next era of pediatric allergy, where early recognition of T2 endotypes, careful exposome analysis and timely initiation of biologic therapy may allow clinicians to prevent or mitigate the development of complex, multi-organ allergic disease.

CONCLUSIONS

T2 inflammation represents the shared immunological backbone of pediatric allergic diseases. Advances in epithelial biology, neuroimmune science, microbiome research and pediatric endotyping have expanded understanding of the atopic march and informed targeted therapeutic strategies. Precision medicine approaches addressing barrier repair, environmental exposures and immune modulation hold promise for improving long-term outcomes.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Ethical consideration

Ethical approval was not required for this article as it is a narrative mini-review and did not involve human participants, animal experimentation or the use of personal data.

Conflict of interest statement

The authors declare no conflicts of interest related to the content of this manuscript.

Author’s contributions

A.L. conceived the manuscript and supervised its development. S.F.R. and R.C. performed the literature review and contributed to writing the first draft. G.L.M. critically revised the manuscript for scientific accuracy. All authors approved the final version and agree to be accountable for the content.

History

Received: November 24, 2025

Published: January 23, 2026

Figures and tables

TABLE I. Type 2 mechanisms in specific pediatric allergic diseases.

Disease	Primary barrier/tissue	Key type 2 drivers (cells, cytokines, alarmins)	Main pathophysiologic features	Clinical hallmarks in children	Targeted therapeutic implications
Atopic dermatitis (AD)	Epidermal barrier (stratum corneum, tight junctions)	Damaged keratinocytes releasing TSLP, IL-25, IL-33; ILC2 and Th2 cells producing IL-4, IL-13, IL-5; eosinophils; mast cells; type 2-activated sensory neurons (IL-4/IL-13/IL-31 responsive)	Filaggrin/loricrin/claudin and lipid defects; increased transepidermal water loss; microbial dysbiosis (S. aureus overgrowth); amplification of itch-scratch cycle; chronic dermal inflammation and remodeling	Early-onset eczema; intense pruritus; lichenification; frequent association with food allergy, allergic rhinitis and asthma (start of the atopic march)	Topical barrier repair and anti-inflammatories; systemic immunomodulators in severe cases; biologics targeting IL-4Rα (dupilumab) to block IL-4/IL-13 and reduce skin inflammation, pruritus and atopic multimorbidity
IgE-mediated food allergy	Intestinal mucosa (small and large intestine) and, in many infants, eczematous skin as site of primary sensitization	Epithelial alarmins (TSLP, IL-33, IL-25); Th2 cells and ILC2; IL-4, IL-5, IL-13; IgE-switched B cells; mast cells and basophils	Increased intestinal permeability; dysregulated oral tolerance; Th2-biased responses to dietary antigens; mast-cell degranulation upon re-exposure; crosstalk with skin barrier dysfunction in AD	Immediate reactions after food ingestion (urticaria, angioedema, vomiting, wheeze, anaphylaxis); frequent coexistence with AD and asthma; risk of progression to EoE in a subset of patients	Allergen avoidance and emergency management of anaphylaxis; oral immunotherapy in selected cases; emerging role of biologics (anti-IgE, anti-IL-4Rα) to modulate systemic type 2 inflammation and facilitate desensitization
Eosinophilic Esophagitis (EoE)	Esophageal squamous epithelium	Epithelial release of TSLP, IL-33 and IL-25; ILC2 and Th2 cells producing IL-5 and IL-13; eosinophils; mast cells and fibroblasts	Basal cell hyperplasia, dilated intercellular spaces and tight-junction defects; dense eosinophilic infiltrate; subepithelial fibrosis, smooth-muscle hypertrophy and strictures; largely non-IgE-mediated T2 inflammation	Food-triggered dysphagia, food impaction, chest/epigastric pain, feeding difficulties and failure to thrive; strong association with AD, food allergy and asthma; often a later manifestation in the atopic march	Elemental or elimination diets; swallowed topical corticosteroids; biologics targeting IL-4Rα (dupilumab) to inhibit IL-4/IL-13 signaling and reduce eosinophilia and remodeling; anti-IL-5/IL-5R under investigation
Allergic rhinitis	Nasal mucosa and upper airway epithelium	Aeroallergen-driven IgE; mast cells and basophils; Th2 cells; IL-4, IL-5, IL-13; epithelial alarmins (TSLP, IL-33); eosinophils	Impaired epithelial barrier and tight junctions; mucosal edema; goblet-cell hyperplasia and mucus overproduction; eosinophilic inflammation extending along the united airways	Rhinorrhea, sneezing, nasal obstruction and itching; frequent ocular symptoms; strong epidemiologic and mechanistic link with pediatric asthma	Allergen avoidance; intranasal corticosteroids and antihistamines; allergen immunotherapy; in selected severe multimorbid patients, biologics targeting IgE or IL-4Rα within a broader T2-high endotype
Pediatric asthma (T2-high endotypes)	Bronchial epithelium and lower airways	Epithelial alarmins; Th2 cells and ILC2; IL-4, IL-5, IL-13; eosinophils; IgE; type 2-modulated sensory and autonomic neurons	Airway eosinophilia; goblet-cell metaplasia and mucus plugging; airway hyperresponsiveness; subepithelial fibrosis and smooth-muscle hypertrophy; in children, frequent coexistence of allergic and non-allergic eosinophilic patterns	Recurrent wheeze, cough, dyspnea and nocturnal symptoms; exacerbations often triggered by viral infections; frequent comorbidity with AD, allergic rhinitis, food allergy and EoE; predominance of T2-high features in severe pediatric asthma	Inhaled corticosteroids and bronchodilators as background therapy; biologics guided by endotype: anti-IgE, anti-IL-5/IL-5R, anti-IL-4Rα, and upstream anti-TSLP; early identification and treatment of T2-high children to prevent long-term remodeling