Respiratory allergic diseases, namely asthma and allergic rhinitis (AR), are among the most common chronic pediatric conditions with prevalence continuing to rise over last decades and are leading healthcare costs. Epidemiological trends show high rates in young children, aged under 10 years, significant comorbidity between conditions (asthma and AR), and a rising recognition of lifestyle's role in microbial, epithelial barrier and immune system dysfunction which collectively drive type 2-driven airway inflammation, the hallmark feature of allergic respiratory diseases.

Strategies aiming to reduce allergy outcomes have included dietary interventions during the pediatric age with immunonutrition and postbiotics. Immunonutrition uses specific nutrients to support the immune system, while postbiotics use microbial-derived compounds to modulate microbiome, epithelial barrier and immune function, and they can work together by modulating the gut-immune axis to reduce inflammation and to promote immune tolerance also through epigenetic mechanisms.

Vitamin D, DHA, quercetin, perilla frutescens, fructooligosaccharides and DHA have been indicated as promising food supplements for and effective immunonutrition action against allergy. Similarly, postbiotics-non-viable microbial preparations with demonstrated biological activity-such as heat-inactivated Lactobacillus rhamnosus GG (LGG) and the gut microbiome-derived metabolite butyrate have been shown to strengthen epithelial barrier integrity, modulate cytokine secretion, and promote regulatory immune responses.

Collectively, these findings suggest that targeted nutritional or microbial-derived interventions capable of reinforcing epithelial barrier function and restoring regulatory immune pathways may offer a promising adjunctive strategy for pediatric allergic airway diseases. Despite the expanding mechanistic evidence, clinical trials evaluating multi-component immunomodulatory nutritional interventions in children with asthma or allergic rhinitis remain scarce, and the translational relevance of these mechanistic pathways has not yet been thoroughly tested in controlled pediatric studies.

Based on this rationale, we designed a clinical study to evaluate the clinical and immunological effects of a multi-component supplement containing immunonutritional compounds and postbiotics focusing on symptom control and immunoregulatory biomarkers in PBMCs from children with allergic asthma and AR.

Inclusion Criteria:

• confirmed diagnosis of asthma and/or allergic rhinitis

Exclusion Criteria:

• non-Caucasian ethnicity,
• age <5 or >12 years,
• known hypersensitivity to any of the ingredients of the study product,
• the presence of chronic systemic diseases,
• immunodeficiencies,
• ongoing allergen immunotherapy,
• treatment with immunomodulators,
• systemic corticosteroids, antibiotics, or pre/pro/synbiotics within the four weeks prior to enrollment and during the 6-month study period,
• participation in other studies,
• any condition deemed by the investigators to interfere with study participation or study outcomes.