Nickel sensitivity: effects of prolonged oral intake of the element

25 nickel-sensitive females were given 10 mg NiSO4 in water in a single dose. 18 experienced generalized or localized flare-ups. 15 days later, 17 of the 25 patients were given gradually increasing daily doses of NiSO4 in water for 3 months. 14 ended the trial without flare-up, 3 had to stop because of intense worsening of cutaneous manifestations. A relationship does exist between the daily oral intake of nickel and its clinical manifestations, but it is not uniform and depends on the changing quantities and, above all, on the manner of intake. It would seem that a 10 mg NiSO4 oral challenge represents a sudden and large intake of the element to which the majority of sensitized subjects are not able to adapt. On the other hand, a gradual intake permits a majority of subjects to adapt to the element. We hypothesize that this behaviour is more likely due to intestinal adaptivity than to immunological tolerance.