to circumcision reducing HIV risk for receptive anal intercourse. Human papillomavirus Human papillomavirus (HPV) is the most commonly transmitted sexually transmitted infection, affecting both men and women. While most infections are asymptomatic and are cleared by the immune system, some types of the virus cause genital warts, and other types, if untreated, cause various forms of cancer, including cervical cancer, and penile cancer. Genital warts and cervical cancer are the two most common problems resulting from HPV. Circumcision is associated with a reduced prevalence of oncogenic types of HPV infection, meaning that a randomly selected circumcised man is less likely to be found infected with cancer-causing types of HPV than an uncircumcised man. It also decreases the likelihood of multiple infections. there was no strong evidence that it reduces the rate of new HPV infection, but the procedure is associated with increased clearance of the virus by the body, which can account for the finding of reduced prevalence. Although genital warts are caused by a type of HPV, there is no statistically significant relationship between being circumcised and the presence of genital warts. Other infections Studies evaluating the effect of circumcision on the rates of other sexually transmitted infections have generally, found it to be protective. A 2006 meta-analysis found that circumcision was associated with lower rates of syphilis, chancroid and possibly genital herpes. A 2010 review found that circumcision reduced the incidence of HSV-2 (herpes simplex virus, type 2) infections by 28%. The researchers found mixed results for protection against trichomonas vaginalis and chlamydia trachomatis, and no evidence of protection against gonorrhea or syphilis. It may also possibly protect against syphilis in MSM. Phimosis, balanitis and balanoposthitis Phimosis is the inability to retract the foreskin over the glans penis. At birth, the foreskin cannot be retracted due to adhesions between the foreskin and glans, and this is considered normal (physiological phimosis). Over time the foreskin naturally separates from the glans, and a majority of boys are able to retract the foreskin by age three. Less than one percent are still having problems at age 18. If the inability to do so becomes problematic (pathological phimosis) circumcision is a treatment option. This pathological phimosis may be due to scarring from the skin disease balanitis xerotica obliterans (BXO), repeated episodes of balanoposthitis or forced retraction of the foreskin. Steroid creams are also a reasonable option and may prevent the need for