As with most forms of sexual activity, anal sex participants risk contracting sexually transmitted infections (STIs). Anal sex is considered a high-risk sexual practice because of the vulnerability of the anus and rectum. The anal and rectal tissue are delicate and do not provide lubrication like the vagina does, so they can easily tear and permit disease transmission, especially if a personal lubricant is not used. Anal sex without protection of a condom is considered the riskiest form of sexual activity, and therefore health authorities such as the World Health Organization (WHO) recommend safe sex practices for anal sex.