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Background: Valid epidemiological tools are required for surveillance of the prevalence of contact allergy. Population based studies including patch testing is the most reliable method, but implies heavy expenses and logistical problems. Clinical data are not representative for the general population and questionnaires concerning contact allergy have a low validity. Self-testing might be a useful method but it has to be validated and evaluated. Objectives: To investigate the validity of self-patch testing for nickel allergy. Methods: Patients from three dermatology clinics were included consecutively when referred to patch testing. In total, 191 patients participated and they were provided with a self-test package including written instructions. The self-test was applied on the arm by the patient, on the same day as the patch test was applied on the back, in the clinic. The patient evaluated the self-test before the patch test reading at the clinic. Results: Patch test at dermatology clinic (‘gold standard’) gave 46/191 (24%) nickel-positive individuals. The sensitivity of the self-test was 72% (95% CI 57–84), the specificity was 91% (95% CI 85–95) and the proportion of agreement was 86% (95% CI 81–91).Conclusions: The validity of self-testing for nickel allergy was adequate in the studied population. To determine whether self-testing is a useful tool for measuring the prevalence of nickel allergy in the general population further studies will be needed.

BACKGROUND: In population-based studies using self-reported nickel allergy, a hand eczema prevalence of 30-43% has been reported in individuals with nickel allergy. In a previous Swedish study, 958 schoolgirls were patch tested for nickel. In a questionnaire follow up 20 years later no association was found between nickel allergy and hand eczema. OBJECTIVES: To investigate further the relation between nickel allergy and hand eczema. METHODS: Three hundred and sixty-nine women, still living in the same geographical area, now aged 30-40 years, were patch tested and clinically investigated regarding hand eczema. RESULTS: Patch testing showed 30.1% nickel-positive individuals. The adjusted prevalence proportion ratio (PPR) for hand eczema after age 15 years in relation to nickel patch test results was 1.03 (95% confidence interval, CI 0.71-1.50). A history of childhood eczema was reported by 35.9%, and the PPR for hand eczema in relation to childhood eczema was 3.68 (95% CI 2.45-5.54). When analysing the relation separately in women with and without a history of childhood eczema a statistical interaction was found. The hand eczema risk was doubled in nickel-positive women without a history of childhood eczema, with a PPR of 2.23 (95% CI 1.10-4.49) for hand eczema after age 15 years. CONCLUSIONS: A doubled risk for hand eczema was found in nickel-positive women without a history of childhood eczema. When analysing all participants, there was no statistically significant difference between nickel-positive and nickel-negative women regarding occurrence of hand eczema. The most important risk factor for hand eczema was childhood eczema. The risk for hand eczema in nickel-positive women may previously have been overestimated.

10% of patch-tested patients have a positive reaction to gold. Most lack clinical symptoms, but allergic contact dermatitis (ACD) to gold is increasing. In this study, 77 dermatological outpatients were divided into 3 groups depending on epicutaneous patch test outcomes: a group positive to gold (EPI+), a group negative to gold (EPI-), and a group with irritant reactions to gold (EPI-IR). Lymphocytes were stimulated in vitro with gold sodium thiosulfate. Proliferation was assessed using the lymphocyte transformation test (LTT), and cytokine secretion was assessed using a multibead array (Luminex; Linco Research Inc., St. Charles, MO, USA), in order to evaluate whether an in vitro method with high diagnostic accuracy could be devised. The EPI+ group showed a significantly increased secretion of interferon (IFN)-gamma, interleukin (IL)-2, and IL-13 and also showed a significantly higher stimulation indexes for LTT, compared to the other 2 subject groups. Sensitivity and specificity were calculated for all methods individually and combined, but IFN-gamma assessment alone was the most accurate method for identifying ACD to gold, with sensitivity and specificity of 81.8% and 82.1%, respectively. This method also identified 87.5% of the EPI-IR subjects as non-allergic. Therefore, assessment of secretion of IFN-gamma should be a valuable complement to patch test for diagnosing gold allergy.

Colophony - also called rosin - is a material obtained from coniferous trees. It is used widely in many products, particularly because of its good tackifying properties. Colophony is also used in paper sizing to increase water resistance. Colophony may cause contact allergy, and around 5% of Swedish dermatitis patients show allergic reactions to colophony at patch testing. There are many case reports of colophony in different products causing contact dermatitis. Often, however, the clinical relevance of a positive patch-test reaction to colophony is difficult to evaluate. The principal aims of the present thesis were to study the prevalence of contact allergy to colophony and of skin disease in individuals with an occupational exposure to colophony; to study the prognosis of dermatitis in colophony-sensitive subjects, and to investigate the outcome of repeated open applications of colophony, thereby trying to elucidate the clinical relevance of contact allergy to colophony. Employees of a tall-oil rosin (colophony) factory (n=180), and of an opera company where colophony was used in dancers' rosin, mascara and wig glues (n=132), were interviewed, examined and patch tested. 3.9% and 2% of these two groups respectively had a positive patch test to colophony. More than every fourth participant showed some kind of skin disease, but only few cases were related to work. Eighty-three patients with previously diagnosed contact allergy to colophony were followed up. 72% showed a positive patch-test reaction to colophony at re-testing. Around one third had hand eczema. There was no significant correlation between colophony exposure and current hand eczema. Adhesive bandages containing colophony and zinc oxide (ZnO), colophony and mixes of colophony and ZnO, were tested in 7 colophony-sensitive subjects to see whether addition of zinc oxide inhibited elicitation of allergic dermatitis to colophony, which has been proposed. No difference in reactivity between colophony and colo