D1.247 - Changes in the sensitization profile in allergic contact dermatitis: comparison between two populations separated by 10 years in a secondary hospital in northern Portugal

Allergic contact dermatitis is a common inflammatory skin disease, and regional contact allergen sensitization patterns may change over time in response to evolving occupational and consumer exposures. We aim to compare the contact allergen sensitization profiles of two patient populations who were referred to the Immunoallergology Department in the Alto Ave region, separated by a 10-year interval.

Retrospective analysis of patch test (PT) results performed in 2014 and 2025, using the standard battery of the Portuguese Study Group on Contact Dermatitis with Chemotechnique Diagnostics commercial extracts. PT were read at 48 h, 72 h or 96 h. Demographic characterization was performed for both populations. 

Concerning the 2014 population, 93 patients were tested and 52 (56%) showed sensitization to at least one allergen. Among sensitized patients, 67% (n=35) were female and mean age was 38 ± 18 years ranging from 5 to 87 years. The most frequent occupations were: textile/footwear factory workers, construction workers, cooks, metalworkers, students, and housemaid. The most prevalent allergens were nickel sulfate (37%), followed by caine mixture (9%) and cobalt chloride (7.5%).

Regarding the 2025 population, 371 patients were tested and 187 (50.4%) were sensitized to at least one allergen. Among sensitized patients, 74.3% were female and mean age was 42 ± 17 years ranging from 6 to 76. The most frequent occupational activities were: textile/footwear factory workers, students, retirees, nurses, and beauticians. The most prevalent sensitization was nickel sulfate in 43.3% of patients, followed by: methylisothiazolinone 0.2%; hydroxymethylacrylate 2% and perfume mixture 8%, each observed in 11.8% and, the third most prevalent allergen found was cobalt chloride 1%, in 10.7%. 

Allergic contact dermatitis continues to be dominated by sensitization to nickel sulfate, with an increase in its prevalence in this region. However, there is a significant change in the sensitization profile, with greater expression of emerging/current allergens such as methylisothiazolinone and acrylates, as well as, an increase in sensitization to perfumes, suggesting the influence of changes in daily lifestyle habits rather than occupational habits. These data point to a dynamic sensitization profile, reinforcing the need for continuous updating of the standard battery and prevention strategies.