Hapten-specific and mast cell-dependent biphasic cutaneous reactions were induced by intravenous application of anti DNP-IgE antibodies and a subsequent skin test. These reactions were also demonstrated in SCID mice, which indicates that T cell-mediated immunity might not be involved in these IgE-mediated cutaneous reactions. Simultaneous application of anti histaminics did not suppress these reactions significantly, while several immunomodulators, such as azelastine, FK506, and prednisolone, significantly inhibited both early and late phase reactions except for the failure of FK506 to inhibit the early reaction. Anti-VCAM-1 antibody and anti-tumor necrosis factor-alpha (TNF alpha) antibody but not anti-IL 5 antibody showed similar suppressive effects on both early and late phase reactions. Mast cell and inflammatory cells other than T cells are thought to play an important role in these IgE-induced biphasic reactions. TNF alpha and/or VCAM-1 are required for tissue accumulation of inflammatory cells in this system.