Late skin-prick-test reactions to malted wheat. Clinical observations and immunohistochemical characterization.

This study reports late skin-prick-test (SPT) reactions in seven bakers and seven control subjects to malted wheat appearing after 6-10 h, and not preceded by an immediate-phase reaction. Two subjects in each group had a history of atopic symptoms and were Phadiatope positive. Serologic IgE analysis (RAST) of normal wheat flour and of malted wheat grain was negative in all subjects. Skin biopsy specimens were obtained 16-18 h after SPT to malted wheat grain and to histamine and from untested skin. The late SPT reactions in all participants had an urticarial appearance, clinically and in routine histology. Immunohistologically mild to moderate perivascular dermal cell infiltrates were observed in both groups, consisting mainly of CD4+ and HLA-DR+ cells. The number of CD1a+ epidermal cells was statistically significantly higher (P < 0.01) in the bakers' prick-tested skin compared to that of the controls, a fact which might reflect preparedness to react upon challenge. There were no statistical differences between the two groups in IgE+ epidermal cells or epidermal cells expressing the high-affinity IgE receptor (Fc epsilon RI). However, there was a correlation between serum-IgE levels and the number of IgE+ epidermal cells. The late skin reactions observed in both bakers and controls were probably more of an irritant or toxic than immune-mediated nature, but they raise the question of whether skin contact with malted flour contributes to an unfavorable prognosis of hand eczema in bakers.