The man with the iron mask did not wear a mask all the time. It is likely, that he only wore it when he was transferred, so that people could not recognize him. If he had worn the mask all the time, this would have led to infections. In addition, as the prisoner was male, the hair growing in his face needed cutting from time to time. The need for wearing a mask is mentioned only twice: In the document which ordered his transfer to the Bastille, and for the transfer to the island near Cannes.