Sensitization to thiourea derivatives among Finnish patients with suspected contact dermatitis

Background: Thiourea derivatives in rubber products may induce contact sensitization and allergic contact dermatitis. Sensitization is most often from neoprene rubber, but the multitude of possible sensitizing products has remained poorly characterized. Objective: The aim of this study was to collect information on the occurrence of thiourea‐related contact allergy and to show novel sources of sensitization. Patients and methods: A mixture of dibutyl‐, diethyl‐, and diphenylthiourea was included in patch test baseline series in five Finnish dermatology clinics during 2002–2007. In addition, an extended series of rubber chemicals was tested in patients with suspected rubber allergy. Sources of sensitization to thioureas were analysed in sensitized patients. Results: Thiourea mix yielded positive patch test reactions in 59 of 15 100 patients (0.39%); 33/59 patients were also tested with individual rubber chemicals. Diethylthiourea was positive in 24/33, diphenylthiourea in 5, and dibutylthiourea in 1 patient. The most common sources of sensitization included various neoprene‐containing orthopaedic braces, sports equipment, and foot wear. Conclusions: The sources of sensitization to thiourea chemicals were detected in most cases. These sources comprise a heterogenous group of products extending from orthopaedic materials to sports equipment.     

Intradermal testing in the diagnosis of allergic contact dermatitis

Contact hypersensitivity may be diagnosed with patch testing or intradermal testing. Although these methods have been used earlier in parallel, patch testing has gradually become the only method in routine diagnosis of contact allergy. Recent findings in corticosteroid contact hypersensitivity have shown that patch testing is not always an optimal method, especially when poor penetrants are used. Therefore, a reappraisal of intradermal testing is presented, based on the literature. Studies employing both patch and intradermal testing are reviewed and the advantages and disadvantages of intradermal tests as compared to patch tests in contact allergy diagnostics are discussed. We find that it might be worthwile to evaluate whether contact allergy to compounds other than corticosteroids may be easier to detect with intradermal than patch test.     

Patch testing in Israeli children with suspected allergic contact dermatitis: A retrospective study and literature review

Background/objectives

Childhood allergic contact dermatitis is recognized as a significant clinical problem. The objective was to evaluate the rate of positive patch tests in Israeli children with clinically suspected allergic contact dermatitis, identify possible sex and age differences, compare results with those in Israeli adults, and review pediatric studies in the literature.

Methods

The study sample included 343 children and adolescents (197 female, 146 male; 1‐18 years of age, mean age 11.8 years) with clinically suspected allergic contact dermatitis who underwent patch testing with a standard pediatric series of 23 allergens at a tertiary medical center from 1999 to 2012. Data on clinical characteristics and test results were collected retrospectively from the medical files.

Results

Ninety‐eight subjects (28.6%) (75 girls [38.1%], 23 boys [15.8%]) had at least one positive reaction. The most frequent reactions were to nickel sulfate, followed by potassium dichromate and cobalt chloride. Nickel sulfate sensitivity was more common in girls, especially those younger than 3 years and older than 12 years. The prevalence of contact sensitization was similar in subjects with and without atopic dermatitis (50% and 51%, respectively).

Conclusion

Nickel is the most common allergen in Israeli children, especially girls. Patch testing should be performed in children with clinically suspected allergic contact dermatitis regardless of atopic background.     

Influence of skin peeling procedure in allergic contact dermatitis

Background:  The prevalence of allergic contact dermatitis in patients who have previously undergone skin peeling has been rarely studied.
Objectives:  We compared the frequency of positive patch test (PT) reactions in a patient group with a history of peeling, to that of a control group with no history of peeling.
Patients/Methods:  The Korean standard series and cosmetic series were performed on a total of 262 patients. 62 patients had previously undergone peeling and 200 patients did not.
Results:  The frequency of positive PT reactions on Korean standard series was significantly higher in the peeling group compared with that of the control group ( P  < 0.05, chi-square test). However, the most commonly identified allergens were mostly cosmetic-unrelated allergens. The frequency of positive PT reactions on cosmetic series in the peeling group was higher than that of the control group, but lacked statistical significance. The frequency (%) of positive PT reactions on cosmetic series in the high-frequency peel group was higher than that of the low-frequency group, but lacked statistical significance.
Conclusion:  It appears peeling may not generally affect the development of contact sensitization. Further work is required focusing on the large-scale prospective studies by performing a PT before and after peeling.     

Occupational allergic contact dermatitis caused by thiourea compounds

Thiourea compounds are mainly used as accelerators in the rubber industry, but also in other industries, e.g., as antioxidants in the graphics industry. Thiourea compounds may provoke allergic contact dermatitis, although the number of reported cases is relatively low. During 1985–1991, we had 5 patients with allergic patch test reactions caused by thiourea compounds. 1 of our patients had to use a knee brace after an occupational accident. He developed allergic contact dermatitis caused by the knee brace, probably because he had become sensitized to diethylthiourea. 2 patients were probably sensitized by diphenylthiourea in neoprene gloves. A florist had an allergic patch test reaction to diphenylthiourea and might have been sensitized by fungicides or pesticides, which break down into thioureas. It is often difficult, however, to detect the source of thiourea compound sensitization. If the patient has contact dermatitis and has been exposed to products that may contain thiourea compounds (or compounds that break down into thiourea compounds), such as rubber, PVC plastic or adhesive, diazo paper, paints or glue remover, anticorrosive agents, fungicides or pesticides, patch testing with a series of thiourea compounds needs to be performed. If patch testing with thiourea compounds is not performed, allergic contact dermatitis caused by thiourea compounds is not likely to be diagnosed.