Ozone as an Immunomodulator—New Therapeutic Possibilities in the Treatment of Immunodeficiencies—A Narrative Review

<b>Research Subject</b>: Primary and secondary immunodeficiencies represent a growing clinical and public health challenge due to increased susceptibility to infections, impaired immune regulation, chronic inflammation, and disturbances in redox homeostasis. The pathophysiology of these disorders involves dysfunction of innate and adaptive immunity, altered cytokine production, oxidative stress, and reduced activity of antioxidant defense mechanisms. In recent years, attention has increasingly focused on the role of oxidative imbalance and chronic inflammation in weakening immune function. Ozone therapy, when used at controlled low doses, induces a hormetic response that triggers adaptive antioxidant pathways, modulates cytokine profiles, and enhances the activity of immune cells. Due to these properties, ozone has emerged as a potential adjunctive therapy aimed at restoring immune homeostasis and improving clinical outcomes in patients with immune disorders. <b>Aim of Study</b>: The aim of this review is to discuss the role of oxidative stress and immune dysregulation in the pathogenesis of immunodeficiencies and to provide an updated overview of current evidence regarding the therapeutic potential of ozone therapy. This article summarizes molecular mechanisms, biochemical effects, and clinical findings related to ozone-based interventions, with particular emphasis on cytokine modulation, redox balance, macrophage function, regulatory T cells (Treg), and NK cell activity. <b>Materials and Methods</b>: This review is based on scientific data retrieved from PubMed, Scopus, and Google Scholar. Included sources comprise randomized clinical trials, observational studies, meta-analyses, mechanistic studies, and review articles published between 1996 and 2025. Keywords used during the literature search included: "ozone therapy", "immunomodulation", "oxidative stress", "inborn errors of immunity", "secondary immunodeficiency", "Treg cells", "redox homeostasis". <b>Results</b>: Analysis of current studies shows that controlled low-dose ozone (typically 10-40 µg/mL) activates the Nrf2/ARE antioxidant pathway, increases enzymatic defense (SOD, catalase, GPx), and reduces levels of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. Clinical trials report improved lymphocyte profiles, enhanced macrophage phagocytic function, increased Treg activity, and reinforced NK cell responses. Patients receiving ozone therapy demonstrate reductions in inflammatory markers (CRP, IL-6, D-dimer), improved redox balance, decreased infection frequency, and better overall immune performance. The therapy is generally well tolerated when administered within established safety guidelines. <b>Conclusions</b>: Available evidence indicates that ozone therapy may serve as a valuable adjunct in the management of immunodeficiencies by modulating immune responses, reducing oxidative stress, and restoring homeostatic balance. Although current clinical outcomes are promising, further multicenter randomized trials are needed to standardize dosing protocols, assess long-term effectiveness, and confirm safety.