"From a medical standpoint, if a tampon's string is getting soiled from urine or fecal material, you should change it. That's just common sense," Dr. Alyssa Dweck, an OB/GYN in Westchester, New York, says.
However, when it comes to infections from tampons, the bigger concern is leaving a tampon in too long, not getting bacteria on your tampon when pooping, says Dr. Matilda Hagan, of the Melissa L. Posner Institute for Digestive Health and Liver Disease at Mercy Medical Center in Baltimore, Maryland. "Even in the absence of tampons, we don't see bowel movements leading to [vaginal] infections," she says.
That said, if you want to remove it each time, that's also fine. "With regard to hygiene, standards are personal," Hagan says.
She also says you could try tucking the tampon's string out of the way with one hand while you wipe with the other.