Nickel‐sulphate‐induced contact dermatitis in the guinea pig maximization test: a dose‐response study

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Abstract
Nickel sulphate is a sensitizer in guinea pigs, but the frequency of sensitization varies from study to study. The dose‐response relationship for NiSO4 6H2O was evaluated in the guinea pig maximization test in this study, 6 intradermal (0.01%–3.0% aq.) and 6 topical (0.25% 10.0% pet.) concentrations were chosen for induction and NiSO46H2O 1% pet was used for challenge, based on the absence of skin irritation in a pilot study. Blind reading was performed. A logistic dose‐response model was applied to the challenge results. At 48 h, a linear relationship was obtained between the intradermal induction dose (but not topical dose) and the response, resulting in a maximum sensitization rate of 40% after 3% i.d. The reactivity disappeared at re‐challenge I week later. Following a booster closed patch on day 35, using NiSO4 pet., the animals were challenged with NiSO4 2% pet. and statistical analyses of 72‐h readings revealed a non‐linear dose‐response relationship, giving a maximum response Frequency of 40% after initial induction with NiSO4, 3% i.d. and 2% topical.