Evaluation of allergic contact sensitization in resistant dermatitis areas in patients with atopic dermatitis

Objectives: This study aimed to detect contact allergies that may accompany cases of resistant atopic dermatitis (AD). Previous studies on this subject have shown conflicting results. With patch testing, we aimed to identify the most common allergens that cause positive reactions, determine their frequency, and compare the frequency of positive reactions between patients with AD and those without AD. This condition is increasingly encountered in dermatology practice and poses an additional burden on patients. Methods: This study was conducted with a total of 62 patients who were diagnosed with atopic dermatitis (AD) either clinically and/or histopathologically and who applied to the Dermatology and Venereal Diseases outpatient clinic of Karadeniz Technical University Faculty of Medicine between September 2022 and February 2024, and underwent patch testing due to suspected allergic contact dermatitis. The study collected data on all patients, including age, gender, demographic characteristics, chronic diseases and regular medications, duration of follow-up with AD diagnosis, systemic or topical treatments received for AD, the number of flare-ups in the last 12 months, accompanying atopic comorbidities, regular daily moisturizer use, findings according to the Hanifin-Rajka criteria, skin prick test results conducted before or during the visit, and serum total IgE levels, all of which were recorded in the case report form. The results of the European standard series patch test applied to the patients were also documented. Additionally, to create a control group, the medical records of 306 patients who did not have an AD diagnosis but underwent patch testing due to suspected allergic contact dermatitis were examined from the hospital's record system. Results: Of the 62 patients included in our study, 19 (30.6%) were male, 43 (69.4%) were female, and the average age was 31.19 (±17.97) years. According to the SCORAD score, 51 (82.3%) patients had mild severity, and 11 (17.7%) patients had moderate severity. While 33 patients (53.2%) regularly used moisturizers, 23 (37.1%) patients received systemic treatment in addition to topical treatment. 39 (62.9%) patients had an accompanying allergic disease. Of the 40 AD patients who underwent a skin prick test, at least one positive result was found in 25 (62.5%), with house dust mites being the most frequently detected allergen (n=17, 42.5%). Patch tests showed positive reactions to at least one allergen in 39 (62.9%) patients. Positive reactions to at least one allergen were observed in 60.5% of female patients and 68.4% of male patients, with no significant effect of gender, disease severity, or presence of additional allergic conditions on the development of positive reactions in the patch test (p=0.550, p=1.000, p=0.404, respectively). The most frequently detected allergens in the patch test were nickel sulfate (n=19/62, 30.6%), potassium dichromate (n=7/62, 11.3%), fragrance mix I (n=5/62, 8.1%), and chloromethylisothiazolinone/methylisothiazolinone (n=5/62, 8.1%). Of the 39 patients with a positive reaction to at least one allergen in the patch test, 20 (51.3%) had a positive reaction to only one allergen, while 19 (48.7%) had positive reactions to two or more allergens. No significant difference was observed in the distribution of positive reactions to one allergen or ≥2 allergens by gender and age (p=0.257, p=0.661, respectively). The control group of 306 patients consisted of 122 (39.9%) males and 184 (60.1%) females, with an average age of 33.47 (±15.58) years. Patch test positivity was significantly higher in AD patients (62.9%) compared to the control group (40.2%) (p=0.001). Although the four most common allergens detected in both groups showed higher positivity rates in the AD patient group, the difference was statistically significant only for nickel sulfate (p=0.016). When AD patients were subdivided by indications, hand eczema was the most common group for patch testing, with 19 patients (30.6%). Positive reactions were observed in 16 (84.2%) of the 19 AD patients and 82 (40.8%) of the 201 hand eczema control group patients, with a significant difference between the two groups (p<0.001). In the 19 AD patients who underwent patch testing for hand eczema, at least one allergen was detected in 16 (84.2%) of them, with nickel sulfate being the most frequently detected allergen (n=9/19, 47.4%) Conclusion: In our study, the rate of positive patch tests in patients with resistant AD was found to be significantly higher than in the control group. The most frequently observed positive allergen, nickel sulfate, can be a trigger both through dietary intake and through contact with commonly encountered items in daily life. The high prevalence of contact allergy in AD patients is noteworthy, and we believe that this should be considered in the management of treatment, particularly when encountering resistance in this patient group. Keywords: atopic dermatitis, contact sensitization, skin patch test