Malondialdehyde (MDA) is a compound that is derived from the peroxidation of polyunsaturated fatty acids. It has been used as a biomarker to measure oxidative stress in various biological samples in patients who are affected by a wide range of diseases. The aim of our work is to provide an updated overview of the role of MDA as a marker of oxidative stress in allergy-related diseases. We considered studies involving both paediatric and adult patients affected by rhinitis, asthma, urticaria and atopic dermatitis. The measurement of MDA was performed on different types of samples. The reported data highlight the role of serum MDA in inflammatory airway diseases. According to the literature review, the oxidative stress status in asthmatic patients, assessed via MDA determination, appears to worsen in the presence of other allergic airway diseases and in relation to the disease severity. This suggests that MDA can be a suitable marker for monitoring the disease status. However, there are several limitations in the considered studies due to the different samples used and the lack of phenotyping and description of the clinical period of patients examined. In cutaneous allergic diseases, the role of MDA is controversial because of the smallness of the studies and the heterogeneity of the samples and patients.

Hymenoptera venom allergy is a cause of anaphylaxis, which significantly affects patients’ daily lives due to the constant fear of accidental stings. Venom immunotherapy (VIT) is the only treatment capable of preventing severe systemic reactions (SSRs). Limited long-term real-life data are available, integrating both clinical and immunological outcomes. A five-year prospective observational study was conducted on 35 patients with a history of SSR who underwent VIT at a tertiary allergy center in Southern Italy; two of them had a diagnosis of systemic mastocytosis. Most patients were sensitized to Vespula, but others to Apis, Polistes dominula and Vespa crabro, reflecting the exposure pattern characteristic of Mediterranean regions. Clinical outcomes following accidental re-stings and serological trends, including total IgE, venom-specific IgE, and baseline serum tryptase, were assessed at treatment initiation and after five years of maintenance therapy. During the entire follow-up, all patients tolerated VIT. No SSRs occurred after accidental stings in 17/35 patients, confirming clinical protection achieved with VIT. Vespula serum-specific IgE presented a highly significant decrease; total IgE, tryptase and specific IgE for Apis, Polistes dominula and Vespa crabro showed a statistically significant decrease. Our findings reinforce the role of VIT as a well-tolerated, effective and disease-modifying treatment in a real-world setting.