Jan E. Wahlberg

Sensitization and testing of guinea pigs with cobalt chloride.

The guinea pig maximization, test was used to study the sensitizing potential of cobalt chloride; 1 % CoCl2, was used for injection and 5 % for topical application. The animals were challenged twice; in series I epicutaneous testing was performed 3 weeks after sensitization and intradermal testing after yet another week. In series II the reverse schedule was used, i, e. intradermal testing after 3 weeks and epicutaneous after 4 weeks. CoCl2 was found to be a grade V allergen. The differences between cobalt‐exposed and control animals (which had been treated with Freunds adjuvant, petrolatum, occlusion, etc.) were statistically significant (P < 0.001), However, the administration of cobalt at the first challenge testing caused this difference to diminish.

Copper – a rare sensitizer

To determine the incidence of patch test reactions to copper, 2% copper sulphate was included incur routine patch test series. The allergic potential of copper sulphate was evaluated by the guinea pig maximization test method (GPMT). 13 of the 1190 eczema patients showed reactions (1.1 %), but they were considered non‐relevant. 3 series of GPMT demonstrated that copper sulphate was a grade I allergen. A critical review of the literature disclosed that several reports on cases of allergic contact dermatitis to copper must be regarded as uncertain or non‐relevant. 4 eases were considered relevant and another 20 cases probably relevant. It is suggested that a test reaction to copper sulphate should be verified by a serial dilution test (SDT). Furthermore, the sensitivity of patients to other metals should be stated, so that one can be aware that false positive reactions from metal impurities, especially nickel, in the copper salt used for testing may occur.

Assessment of skin irritancy: measurement of skin fold thickness

It is desirable to use more objective methods than visual scoring for the assessment of skin irritancy reactions. The edema, or fluid accumulation in the exposed skin sites, can be accurately measured by a caliper and this alternative method of assessment is evaluated from different aspects. Sodium lauryl sulfate (SLS) and non‐anoic acid in different concentrations were applied daily to human and animal (rabbit and guinea pig) skin, and a dose‐response relationship established. Higher concentrations of the irritants induced an earlier response. With 5% SLS as the test substance and the increase in skin fold thickness as the single parameter of skin irritancy, the guinea pig was found to be less reactive than rabbit and man. Measurement techniques, reproduceability and advantages and disadvantages with different animal models are discussed.

Health screening for occupational dermatoses in house painters

During 1976–77 a field investigation was carried out into skin diseases among house painters in Stockholm, Sweden. The study was divided into three stages: I. questionnaire investigation, II. examination of painters who reported skin diseases, and III. patch testing and final classification. Of the 2,622 painters registered on 30 November 1976, 2239 (85.4 %) answered the questionnaire. Current dermatoses were reported by 373 painters (16.7 %) and of these, 227 were examined by us, 40 had recently been examined, and 106 did not attend. Occupational contact eczemas were diagnosed in 87 cases, and it was doubtful if the dermatoses were occupational in an additional 56 cases. A prevalence of 3.9 % was suggested, but this represents a minimum figure. Chloracetamide was found to be an important cause of occupational contact eczema. A personal and/or family history of atopy was common among the affected painters. Solvents were widely used for skin cleansing; there is a great need for continuous information on protective measurements, and on skin cleansing and care. It is concluded that field investigations give higher and probably more reliable prevalence figures for occupational dermatoses than data compiled from outpatient clinics.

Allergenic potential of abietic acid, colophony and pine resin-HA. Clinical and experimental studies.

Resin acids are considered to be the main allergens in colophony (rosin). Tall oils also contain resin acids and may then be potential sensitizers. A resin acid concentrate (pine resin‐HA) together with Chinese colophony were included in our standard series and applied on 563 patients with contact dermatitis. Fourteen showed an isolated sensitivity to colophony and two to pine resin‐HA. Six patients reacted to both test compounds. Guinea pig maximization tests (Magnusson & Kligman 1969) showed that pine resin‐HA (2 series) was a grade I allergen, abietic acid a grade III allergen and colophony a grade IV allergen. The risk that the resin acids in tall oils would induce contact sensitivity to workers exposed to tall oil‐containing products like cutting fluids and cleansing agents is considered to be minimal.

Routine patch testing with cadmium chloride

During a 22‐month period, 2.0% cadmium chloride in distilled water was included in our routine patch test series. Twenty‐five of 1502 eczema patients showed reactions (1.7 %), but none had any relevant history. At serial dilution test only one patient reacted to 1.0 % cadmium; all the other dilutions applied gave negative reactions. Analysis by atomic absorption spectrophotometry of the cadmium chloride used for patch testing showed that it contained less than 1 μg/g of chromium, copper, cobalt and nickel. The conclusion is that no certain case of contact allergy to cadmium chloride has been revealed. An experimental study using the guinea pig maximization test is in progress.

Sensitization and Testing of Guinea Pigs with Nickel Sulfate

Experiments in passive transfer of nickel allergy require highly sensitive guinea pigs and a reliable and technically usable test method. A comparison was made between two sensitization methods, the guinea pig maximization test of MAGNUSSON and KLIGMAN (MK) and a combined injection and painting method devised by POLAK and TURK (PT). Intradermal injection was chosen as test method. The reactions to the test were greater than those of normal animals and the differences were statistically significant. With testing before the start of sensitization it was found difficult to obtain highly sensitive animals (tolerance). PT painting resulted in rather higher sensitivity with Triton X-100 than with sodium lauryl sulphate. In a comparison between the MK and PT methods, no difference in effectiveness was found provided that the animals had not been pretested. Repeated PT injections and paintings caused a further increase of the sensitivity, but the toxicity of nickel is a limiting factor.

Contact sensitivity to quinidine sulfate from occupational exposure.

Three workers exposed to quinidine sulfate became sensitized after short exposure times (2–3 months). They were patch test positive to quinidine in different vehicles, hut negative to the diastereoisomer quinine. Guinea pig maximization tests demonstrated quinidine and quinine to be grade V allergens according to the classification of Magnusson & Kligman, When challenged for cross reactivity, the animals sensitive to quinine did not react to quinidine. Among the quinidine‐sensitive guinea pigs, three of 20 (P > 0.05) reacted when challenged with quinine.

Routine patch testing with Irgasan DP 300

lrgasan DP 300® was introduced on the Swedish market in 1968. The annual sale is 3000-4000 kg (1975). It has increasingly replaced hexachlorophene in soap and other cosmetic products. lrgasan was subjected to our standard test in May 1973. The same concentration was chosen as used previously for hexachlorophene (0.5%). As appears from Table 1, 432 patients were tested and all were negative. After the use of a concentration of 1% in ethanol in a Swedish study, we changed to this test solution. Tests were made on 470 patients, all of whom were negative. Since the publication of Roed-Petersens and Aukens report in August 1974, the same concentration has been adopted as that proposed by them: 2% in vaseline. During the period August 1974 to December 1975, 1100 patients were tested and two were positive.

Guinea pig maximization test method – Cadmium chloride

In this study the same experimental design as for cobalt, beryllium, copper and molybdenum compounds (Wahlberg & Boman 1978, Boman et a!. 1979) was used. One group of guinea pigs was actively sensitized with cadmium chloride (Mallinckrodt, analytical reagent) and the other group (control) was treated in the same way (Freunds complete adjuvant, petrolatum, occlusion, etc.) as the first group except for the test compound. The animals were kept in plastic cages, challenged simultaneously after 3 weeks and the readings were performed blind.