Vitamin C in Allergy Mechanisms and for Managing Allergic Diseases: A Narrative Review.

Allergic diseases share a type 2 immune reaction and elevated oxidative stress, contributing to disease pathogenesis and exacerbations. Vitamin C (ascorbic acid), a fundamental exogenous antioxidant, has been hypothesized to attenuate these pathological mechanisms. This narrative review critically examined the most recent evidence concerning the role of vitamin C in preventing and managing allergic diseases, including asthma, allergic rhinitis, and atopic dermatitis. This narrative review consisted of three steps: conducting the search, reviewing abstracts and full texts, and discussing results. For this reason, we consulted the PubMed database to detect the pertinence of studies according to the review's conduct. The final search ended in March 2025 and included English-language-based international articles, online reports, and electronic books. The keywords "vitamin C and allergic disease" and "vitamin C and immune system" were used. After the complete search, we read the abstracts to ensure that they concerned the topic of interest. Recent evidence suggests a protective role for vitamin C in asthma, with several studies reporting reduced oxidative stress markers, improved lung function, and decreased airway inflammation following regular intake or supplementation. Higher dietary vitamin C intake correlates with lower asthma prevalence and severity, particularly in pediatric populations. Conversely, the findings regarding allergic rhinitis and atopic dermatitis are heterogeneous. While topical ascorbic acid derivatives show promise in atopic dermatitis models, oral vitamin C intake does not appear to affect allergic rhinitis or dermatitis risk significantly. Vitamin C demonstrates potential as an add-on therapy in asthma management by attenuating oxidative stress and type 2 respiratory inflammation. However, its role in allergic rhinitis and atopic dermatitis remains less clear. Further multicentric, well-designed clinical trials are necessary to establish definitive guidelines for vitamin C supplementation in allergic disease management.