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From 15 May to 15 December 1994, 2943 patients suspected of having contact dermatitis (1955 women, 988 men) were patch tested with methyldibromoglutaronitrile 0.3%, 0.1% and 0.05% pet. 119 patients (4.0%; women 4.1%), men 3.8%) proved to be allergic. 71% of the reactions were considered to be relevant. In 2/3 of the patients, causative products were cosmetics, in 1/3 moistened toilet tissues. Testing with methyldibromoglutaronitrile at lower concentrations (0.05% and 0.1%) and with commercial allergens (Euxyl® K 400 and methyldibromoglutaronitrile, both containing methyldibromoglutaronitrile 0.1 % >), resulted in a number of false-negative reactions. All preserv atives in the European standard series had lower scores than the 4% positive reactions to methyldi bromoglutaronitrile (formaldehyde 2.0%), MCI/MI (Kathon® CG) 3.2%, parabens 1.0%o, quaternium-15 1.3%). It is concluded that methyldibromoglutaronitrile (present in the commercial pre servative Euxyl® K 400) is an important contact allergen in the Netherlands in cosmetics and moistened toilet tissues. It should be added to cosmetics series and to proctological series. The optimal test concentration is unknow, but may be 0.3% pet. The concentration o f 0.1% methyldi bromoglutaronitrile in the currently available commercial allergens appears to be too low, resulting in a number of false-negative reactions.

Local cytokine profiles in skin biopsies from allergic and irritant patch test reactions were determined by in vivo immunohistochemistry to differentiate between these 2 clinically identical afflictions especially at the time of final reading in diagnostic patch testing. Biopsies were taken from established allergic persons after specific allergic patch test.‐, to epoxy resin (1%) and formaldehyde (1%) and from non‐allergic individuals with irritant patch tests to sodium lauryl sulfate (10%) and formaldehyde (8%). At 72 h after application of the agents, significantly enhanced frequencies of dermal infiltrating cells, producing IL‐1α, TNF‐α. IL‐2. and IFN‐γ per 100 infiltrating cells in the dermis. were observed in allergic as well us irritant patch test reactions, as compared to normal skin. Significantly higher frequencies of IL‐ Iα‐producing cells were observed in biopsies from epoxy resin (1%) allergen‐affected and sodium lauryl sulfate (10%) irritant‐affected skin as compared to formaldehyde (1%) allergen‐affected skin. In addition, significantly higher frequencies of TNF ‐α reproducing cells were observed in epoxy resin allergen‐affected skin us compared to Formaldehyde (1%) allergen‐affected and formaldehyde (8%) irritant affected skin. The allergic and irritant patch test reactions showed similar levels of expression of the Thl cytokines IL‐2 and IFN‐γ in the dermis. confirmed by probe based detection of IL‐2 mRNA and IFN‐γ‐ mRNA, In conclusion, the described similarity shows that allergens and irritants can induce the same profile of IL‐la. TNF‐α. IL‐2. and IFN‐γ production, resulting in the near impossibility of discriminating between allergic and irritant contact dermal is at the lime of patch test reading.

The possibility for patch testing procedures to detect contact allergy was examined in 85 hospitalized patients with forms of psoriasis. Exclusion criteria were active lesions on the back, the use of strong topical corticosteroids, methotrexate, cyclosporin and UV therapy. After screening, a group of 47 patients with different forms of psoriasis were selected for patch testing. Personal history, including topical treatment, occupation and domestic circumstances, were reasons to extend the standard series of allergens. Tars, nickel sulfate, perfume and balsam of Peru scored high. The overall positive rate was 68%. This is higher than that observed in earlier studies. The unexpected results are discussed in the light of the possible mechanism of action.