Idiotypes are molecular clues used to explore the specificity and diversity of immune response. In the present study, anti‐idiotype antibodies were used to neutralize the pathogenic effects induced by the injection of pemphigus immunoglobulin(Ig)G into BALB/c mice. To achieve our goal, antidesmoglein 1 IgG was obtained from a patient with pemphigus foliaceus with high titer of antiepithelial antibodies. The IgG was isolated by ion exchange chromatography, then digested by pepsin. F(ab′)₂ fragments were purified in Sephacryl S‐300 and injected in rabbits to produce anti‐idiotype antibodies. The rabbit sera reacted with the pemphigus F(ab′)₂ fragments. Eleven pemphigus foliaceus sera were recognized by the anti‐idiotype serum at the light or heavy chains whereas bullous pemphigoid and normal IgG were negative. Neonatal BALB/c mice injected with pemphigus IgG developed intraepidermal blisters, mimicking the clinical and immunopathological features of the pemphigus. In contrast, the animals treated with anti‐idiotype antibodies and pemphigus IgG did not develop blisters. Thus, anti‐idiotype antibodies neutralize in vivo the pathogenic effects of pemphigus IgG.