Heavy Metal Sensitization in Contact Dermatitis: Age-Sex Interaction Analysis of 402 Patch-Tested Patients

Background Contact dermatitis is a common inflammatory skin disease whose diagnosis relies on allergen identification via patch testing. However, the positive rates, distribution patterns of allergens, and their associations with demographic and immunological indicators require systematic analysis.. Methods This study enrolled 402 patients with suspected contact dermatitis. Allergen positivity was determined by patch testing, with analyses of associations across gender, age, total IgE, and eosinophil (EOS) levels. Statistical significance was evaluated using Spearman correlation and chi-square tests. Results The overall positivity rate was 62.69% (252/402). Among the top 21 allergens, cobalt chloride (22.89%), nickel sulfate (19.90%), and thimerosal (62.5% strongly positive +++ cases) were predominant. Age stratification revealed: ≤18 years group: Eczema (40%) and plant extract allergies predominated (fragrance mix I positivity: 18.2%); 19-35 years group: Notable sensitization to disperse red 17 (15.2%) and nickel sulfate (9.6%); 36-50 years group: Highest cobalt chloride positivity (24.6%) with 50.0% strong nickel sulfate reactivity (+++); >50 years group: Thimerosal (+++ in 10 cases) and rosin (+++ in 6 cases) were primary allergens. No significant differences in positivity distribution were observed across gender or age groups (p > 0.05). Total IgE and EOS levels showed no statistically significant correlations with allergy severity indicators (number of positives, mean/maximum intensity; p > 0.05).Conclusion Metals and mercury-containing preservatives are core allergens in contact dermatitis. Age-specific sensitization patterns align with exposure characteristics, yet allergic intensity lacks significant immunological correlations. Clinicians should enhance allergen screening for high-risk populations (e.g., occupationally exposed young adults) and promote alternatives to mercury-containing preservatives.