Elevated serum IgE levels were present in pemphigoid patients but not in those with pemphigus. The exact pathophysiologic or immunologic explanation of the elevated serum IgE levels in pemphigoid has not been determined yet.
Arbesman CE, Wypych JI, Reisman RE, Beutner EH. IgE Levels in Sera of Patients With Pemphigus or Bullous Pemphigoid. Arch Dermatol. 1974;110(3):378-381. doi:10.1001/archderm.1974.01630090016003