It’s highly likely that large chunk of you watching this video have needed stitches at some point.

It’s also likely that your doctor was super weird about getting them removed on time. That’s because the consequences of leaving them in there can be … not fun.

External stitches, or sutures, are used to hold two sides of an open wound together while they heal. As a general rule, if your cut is longer than a centimeter, your doctor will probably use sutures to get it closed. Open wounds are traditionally not awesome for a bunch of reasons.

Infection is the main worry, because bacteria and other nasty things can get in if there’s an opening. So stitches are great, but you should definitely listen to instructions about removing them, for two reasons: The first is infection again. It might seem weird that the thing preventing infection can also cause it, but sometimes the sutures can get buried.

And yes, that’s a horrifying as it sounds. Patients who undergo eyelid surgery often have this happen. Tissue can grow around the stitches and they need to be dug out of their face.

I mean, there’s anesthetic involved, but still: ergh. The other reason you should get them removed on time is entirely cosmetic and not such a big deal compared to life-threatening infection. After about 4-14 days, depending on their location, stitches can cause permanent scarring.

This gets nastier the longer they’re left in. Because of the risk of scarring, if the wound is on the patient’s face, doctors often won’t use stitches at all. There are other options, like a type of glue that dissolves after a certain amount of time.

It’s made out of a polymer called cyanoacrylate, the sticky stuff that’s also used to make super glue. You may also have heard of those stitches that dissolve after a while, but they’re mostly used for more serious injuries or surgeries where doctors need to do some stitching inside body. They’re not gonna cut someone open again just to remove the stitches, so they use special stitches made out of biodegradable organic material instead, which are designed to be absorbed by your body.

Sometimes, doctors will use these absorbable sutures externally, too. But most of the time they stick to the regular, non-absorbable kind, for a few main reasons: For one thing, absorbable sutures can take a month or two to dissolve. But the wound usually heals way before that, and then you’re just left with strings in your skin for no reason.

They also tend to cause more inflammation than regular sutures as the body absorbs them, which can lead to more scarring in some cases. Plus, regular sutures are often stronger, which means there’s less of a risk of the wound opening up again. So, unless the stitches are inside your body or your face is being held together with the medical equivalent of super glue, you’ll probably have to get them removed.

But it’s worth it, even if it does kind of feel like your skin is unraveling as they’re being pulled out. Thanks for asking, and thanks especially to our patrons on Patreon who keep these answers coming. If you’re interested in what happens when you leave other things inside your body, you can check out our video on what happens if you don’t take out a splinter.