Studies on the effect of systemic administration of sensitizers in guinea-pigs with contact sensitivity to inorganic metal compounds. II. The flare-up of previous test sites of contact sensitivity and the development of a generalized rash.

The intravenous injection of K2Cr2O7 produces a specific flare-up of old sites of contact sensitivity to K2Cr2O7 and, in very highly sensitive animals, there is also a generalized rash all over the body. A similar specific flare-up of old contact sensitivity site to BeF2 can be produced by the intravenous injection of Be lactate. Histological examination of the flare-up site shows an infiltration with polymorphonuclear leucocytes. Flare-up reactions can be blocked by an antiserum directed against polymorphonuclear leucocytes but not by anti-LNPF serum which blocks contact sensitivity reactions specifically. It is suggested that the flare-up reaction is not a cell-mediated immune reaction but could be similar to the Arthus reaction and is possibly mediated by humoral antibodies. The histological appearance of the generalized rash is similar to that seen on examination of the rash produced by serum sickness in the guinea-pig. The rash can be produced by absorption of K2Cr2O7 from an abraded area of skin as well as by intravenous injection.