Allergic Contact Dermatitis: A Comparative Study of Elderly and Young Over Time

Background: Delayed hypersensitivity reactions, such as allergic contact dermatitis (ACD), present distinct patterns across age groups. While age-related immune changes are well-documented, their impact on patch test outcomes and allergen sensitization in elderly individuals remains underexplored. Objectives: This study assessed age-related differences in allergen sensitization and immune response in ACD by comparing patch test reactions between elderly individuals (≥ 65 years) and younger adults (18−40 years). In addition, findings were also compared with a similar study conducted between 1997 and 2001. Methods: A retrospective cohort study analysed a total of 2377 patients who underwent patch testing at the University of Padua's Dermatology Clinic from 2006 to 2019. The study included 709 elderly and 1668 younger adults, evaluating standard allergen series for differences in sensitization based on age, sex and affected body sites. Results: Elderly patients had a lower rate of positive patch test reactions (62.6%) compared to younger individuals (71.5%) and exhibited fewer cases of multiple contact allergies. Allergic reactions were more frequently localized to the face in the elderly, while younger adults showed more cases of hand dermatitis. The intensity of allergic reactions was generally milder in the elderly. Strong reactions were significantly more frequent among younger individuals, especially for nickel. Sensitization patterns differed, with younger adults more commonly reactive to nickel and cobalt, while balsam of Peru and neomycin were more prevalent in the elderly. Conclusions: Although aging is associated with a decline in immune responsiveness, elderly individuals remain significantly sensitized to allergens such as balsam of Peru and neomycin. Compared to data from 1997 to 2001, both age groups show an increased prevalence of sensitization and multiple contact allergies, suggesting a temporal trend. These findings highlight the importance of considering age-related immune changes when diagnosing and managing ACD in older patients.