The objective of the present study is to describe any changes in the prevalence of sensitization to common contact allergens in patch-tested patients over a 12-year period. Attention is given to possible effects of preventive strategies introduced in Denmark regarding nickel and chromate sensitization during that period, and particular areas of concern are identified. Members of the Danish Contact Dermatitis Group collected patch-test results from consecutive eczema patients as well as information about exposures and demographic variables over a 6-month period in 1985-86. The investigation was repeated in 1997-98 in the same clinics, at the same time of year, using identical methods and patch-test substances, including nickel sulphate 5%, potassium dichromate 0.5% and fragrance mix 8%. Nickel was the most common contact allergen in both study periods, followed by the fragrance mix. In children 0-18 years of age, the frequency of nickel allergy decreased from 24.8% in the first study period to 9.2% in the second study period (P < 0. 0008). Fragrance mix allergy doubled in frequency from 4.1% in 1985-86 to 9.9% in 1997-98, an increase that affected all age groups. Contact allergy to potassium dichromate decreased significantly from 3.0% in the first period to 1.2% in the second period (P = 0. 001). The decrease was seen in both sexes and was most pronounced among those of working age. No other significant changes were found in the frequency of sensitization to common allergens over the 12-year observation period.

Overall, the disease had improved 6 months after the dermatological examination: nevertheless, many patients continued to have significant symptoms. Dermatologists should pay special attention to patients with frequent eruptions and to unskilled workers.

The relationship between clinical type of hand eczema and aetiological diagnosis fitted with general experience, but no simple relationship was found. This emphasizes that patch testing and exposure analysis are mandatory. Hyperkeratotic palmar hand eczema was identified as a distinct clinical subtype.

The 1% prevalence of epoxy resin contact allergy is equivalent to reports from other countries. The high occurrence of epoxy resin exposure at work, and the limited use of protective measures, indicate that reinforcement of the law is required.

Of 28 patients with chronic nickel dermatitis 17 experienced aggravation following oral ingestion of 2.5 mg nickel, but not a placebo tablet. The dermatitis of 9 of the 17 patients improved during a period of 6 weeks on a low nickel diet. The dermatitis of 7 of the 9 patients flared again when a normal diet was resumed. Nickel excretion over a 24-h period was measured for 14 of the 17 patients by atomic absorption spectrophotometry before, during, and after the diet. Reduced excretion was seen during the diet with no statistically significant difference between patients whose dermatitis improved during the diet and those whose dermatitis showed no change.