The tissue & natural lubrication in the vagina & anus are different. The vagina has 40 layers thick with cells that are stacked like bricks making it harder for the HIV virus to penetrate and get through, while the anus is ONLY 1 cell layer thick. Anal and rectal tissue also don’t provide natural lubricant (which helps to prevent tearing), which the vagina does. Additionally, while the vagina is “self-cleaning,” feces that pass through the rectum contain bacteria, so tears in anal/rectal tissue is at a greater risk of getting infected than tears in vaginal tissue.
For tips on how to reduce risks during anal sex, click here!