[Distribution characteristics and clinical significance of exposed allergens in different age groups]

Objective: This study aimed to assess the patch test positivity rate, allergen distribution, and their associations with demographic characteristics and immune indicators in patients with allergic contact dermatitis (ACD). Methods: A retrospective medical record analysis was conducted on 402 patients suspected of ACD (338 females, median age 38 years; 64 males, median age 43 years) seen at Xuanwu Hospital, Capital Medical University between June 2023 and June 2024. Standard patch tests (using 100 haptens from the Chinese baseline series) were administered, and serum total IgE and eosinophil levels were measured. Statistical analyses included chi-square tests, t-tests/Mann-Whitney U tests for group comparisons, and Spearman correlation for associations. Results: The overall patch test positivity rate among the 402 patients was 62.69% (252/402), with 85.71% (216/252) showing sensitivity to the top 21 allergens. Predominantly, the affected individuals were females (84.26%, 182/216) aged 19-35 years (36.57%, 79/216). The primary sensitizers were cobalt chloride (22.89%, 92/402) and nickel sulfate (19.90%, 80/402). The highest proportion of severe reactions (+++) was observed with thimerosal (10/16). Males exhibited significantly higher positive risks for carba mix (OR=5.10, P=0.002) and octyl gallate (OR=2.64, P=0.047) compared to females. The age-stratified results revealed that the cobalt chloride positive rate was abnormally increased to 76.72% (50/65) in the 36-50 years age group, a rate significantly higher than those observed in the ≤18 years group (20.00%), the 19-35 years group (21.51%), and the >50 years group (16.13%; all P<0.05). In contrast, the >50 years age group exhibited the highest positive rate for nickel sulfate among all age groups at 20.96% (13/62). No significant correlations were found between the number of positive patch tests, reaction intensity (average/maximum), and total IgE (r=-0.075-0.063), absolute and percentage of eosinophils (P>0.05). Clinically, eczema prevalence in the>50 age group was 22.58% (14/62), with ACD complicated by allergic dermatitis being the most common (16.67%, 36/216). Conclusion: Nickel sulfate and cobalt chloride are primary sensitizers for ACD. Sensitization patterns across age groups are similar and unrelated to IgE/EOS levels. The higher incidence of severe reactions to thimerosal may be linked to heightened sensitization to mercury-containing products like vaccine preservatives. The notably increased cobalt chloride positivity in the 36-50 age group suggests a unique exposure risk, while the higher prevalence in females may be associated with contact with nickel/cobalt-containing items such as jewelry and cosmetics.