Revisiting Shellfish as the Leading Allergen in Adult-Onset Food Allergy

Adult-onset food allergy (AOFA), referring to food allergies that first develop in adulthood, has received growing attention in recent years, reflecting the broader rise of immunoglobulin E (IgE)-mediated food allergies. Despite limited dedicated research, a small but expanding body of observational and clinical data offers insight into its characteristics, particularly the frequency of implicated allergens. In this narrative review, the widely cited claim that shellfish are the most common allergen associated with AOFA is critically examined. To assess this claim, relevant peer-reviewed observational studies, published in English and primarily indexed in the PubMed database between 2000 and 2025, were reviewed. Studies were selected based on their focus on adult populations and the availability of specific allergen data. Shellfish were consistently identified as one of the most frequently reported allergens in multiple studies conducted across diverse geographic regions. However, substantial variation in study design, population characteristics, diagnostic criteria, and reporting practices hindered direct comparisons. Variability in reported prevalence rates and methodological differences further complicated interpretation. Additionally, limitations such as reliance on self-reported diagnoses and inconsistent use of diagnostic tests were identified as factors that limit the generalizability of current findings. In summary, although shellfish are frequently reported as a leading allergen in AOFA, current evidence remains inconclusive. Misidentification of the most prevalent allergens could potentially influence clinical guidance and public health interventions. The need for rigorous, large-scale epidemiological studies employing standardized definitions and diagnostic protocols is therefore emphasized. A clearer understanding of allergen prevalence in AOFA will enable more effective clinical risk assessments and support the development of targeted public health strategies.