Persistent subcutaneous nodules arise at the injection sites of aluminium hydroxide-absorbed hyposensitization solutions. We present a hitherto unreported phenomenon in aluminium granuloma. Two years after specific immunotherapy, a patient suffered increasingly from urticaria. Besides inflammatory infiltrates surrounding necrotic areas, microscopy of the specimen revealed numerous mast cells surrounding the necrotic tissue areas. The histological phenomenon of increased mast cell populations in aluminium granuloma might reflect the association with urticaria, which is probably more frequent than previously reported.