Subepidermal bulla containing eosinophils with an eosinophilic inflammatory cell infiltrate in the superficial dermis (H and E staining, magnification ×100) (a); detail of eosinophils in the subepidermal blister (H and E staining, magnification ×400) (b). Direct immunofluorescence tests show deposition of IgG (c) and C3 (d) at the basement membrane zone (200x).