The flare reaction and its rash component in guinea-pig oral mucosa and skin.

Flare and rash phenomena in allergic individuals may occur after fresh contact with antigen, particularly if administered systemically. Experiments demonstrated both the phenomena at various epithelial sites in dinitrochlorobenzene (DNCB) sensitized guinea-pigs, after intravenous dinitrobenzene sulphonic acid sodium salt (DNBSONa). The typical appearance of an epithelial target lesion had a component due only to the rash. The oral mucosa was found to undergo changes due to the rash component some hours before comparable skin sites. During the time span of the experiments, the oral mucosal reactions dispersed more rapidly than concurrent reactions at epidermal sites. Histological evidence of the mainly cell-mediated immune pathogenesis of flare and rash reactions was provided by mononuclear cell counts at the target sites. Aspects of the early appearance of the oral lesions, acting as possible indicators of later skin manifestations, are discussed.