The dude in this story may seem clueless — but it turns out that a lot of people don’t understand why tampons come in different sizes, even some people who wear them. That’s because, despite being referred to as “sizes,” light, regular, and super tampons aren’t designed for small, medium, and large vaginas — they’re designed to accommodate light, medium, and heavy menstrual flows. In other words, a tampon's “size” actually refers to its absorbency.
Some people may notice that their menstrual flow varies from day to day. Typically, it's heaviest on the first or second day, and lightest towards the end of the period. So someone whose period lasts five days — pretty common — might use a super tampon on the first and second day, a regular tampon on the third and fourth day, and a light tampon on the fifth day. Many tampon brands sell “multipacks” containing a mix of tampon sizes for just this reason.
If you wear a light tampon on a heavy flow day, you’ll need to change it frequently or risk leakage. If you wear a super tampon on a light flow day, it may be uncomfortable, and could even lead to micro-tears in your vagina when you remove it.
But what's dangerous, according to Planned Parenthood, is leaving your tampon in considerably longer than the suggested time. Regardless of how heavy your flow is, it’s best to change your tampon every four to eight hours — though you can change it more frequently if you need or want to. This guideline is in place to lessen the risk of developing health conditions caused by the growth of bacteria. That includes bacterial vaginosis, a common vaginal infection that leads to itchiness and discharge; and toxic shock syndrome, a very rare but serious complication that causes a rash and flu-like symptoms, and if it progresses, can lead to renal failure or death.
Katharine O'Connell White, MD, the director of the Fellowship in Family Planning at Boston Medical Center, previously told Refinery29 that changing your tampon frequently is the best way to promote vaginal health. If your flow is moderate, it’s better to wear regular tampons and change them every four hours, than it is to wear super tampons and change them every eight hours. “The more frequently you change them, the fresher they are, and the less likely the bacteria will grow,” she said.