Anal sex is defined as inserting a penis, finger or other object into the anus for the purpose of sexual stimulation.
Anal sex may cause pain and bleeding, but repeated activity usually results in these problems disappearing. The main risk is that oversize dildos may be used and cause anal damage, or that objects may be pass beyond the anal sphincter, enter the rectum, and cannot be retrieved without medical help.
A wide range of sexually transmitted diseases (including AIDS, syphilis and genital herpes) may be caught from anal sex, by both the penetrator and recipient. Other problems may include pruritus ani (itchy anus), proctalgia fugax (anal pain) and dermatitis.
It is very important that anything that has been in the anus should not go into the vagina or mouth unless it has been thoroughly cleaned.