Anal herpes is an infection caused by the herpes virus that erupts as sores or blisters around the anus, the opening through which bowel movements pass. Syphilis , chancroid , and donovanosis are infections that can cause different types of lesions around the anus. The same virus that causes genital herpes can cause lesions in the genitals, anus, or perianus. But, not everyone with genital herpes has anal herpes. If you have obvious symptoms of anal herpes, your doctor may decide to treat you after a physical exam. Because several different sexually transmitted microorganisms can cause anal symptoms, your doctor may want to verify the exact cause of your infection with testing before starting treatment.