♪ INTRO ♪ Warts are rough, fleshy bumps that usually pop up on fingers or hands.

And if you’ve ever had one, you might wonder what the heck it is and where it came from. You might’ve heard the claim that warts come from touching toads, because they have warty-looking bumps on their skin.

Hopefully you already know that’s a myth. But even though toad bumps aren’t contagious, there’s a grain of truth to the idea. Because warts are a kind of contagious skin infection.

Warts are actually caused by human papillomavirus, or HPV. It’s the same kind of virus that can cause cervical cancer and other health issues, depending on the specific strain and where the infection is. In the case of warts, the virus gets into the top layer of your skin, called the epidermis, through an opening like a scratch.

Once it’s in, the virus causes epidermal cells to go into reproductive overdrive. That’s what actually produces the wart. And if you look closely at a wart—because, you know, who doesn’t want to do that—you might see little black specks dotting the surface.

Those are the blood vessels that give the wart food and oxygen. Because they’re caused by a viral infection, warts are contagious. You can get HPV through skin-to-skin contact with someone who has warts, or by touching something that a wart has also touched, like a towel or a nail file.

Once you have the virus, you can also spread it to other parts of your own body. A wart that spawns more warts can be called a mother wart. Everyone’s immune system is different, so not everyone who picks up a strain of HPV will actually develop warts.

We don’t really know why some people are more prone than others, but children seem to be especially susceptible, probably because their immune systems are still developing. Some warts go away on their own, but it can take a year or more. But if you don’t want to wait and risk spreading them, you can try over-the-counter treatments like salicylic acid, which kills off the top layer of infected skin.

Some people even think covering warts with duct tape can help, but it’s mostly anecdotal evidence. Nobody really knows why duct tape might work, but it could have to do with depriving the skin of oxygen, or just peeling dead skin cells away. If you go to your doctor, treatment options open up even more.

A doctor can freeze off warts, prescribe creams or medicines, or even remove them surgically. Whatever treatment you choose, at least you know who not to blame for warts. Leave those poor toads alone.

Thanks to our Patreon patron Heather for asking, and thanks to all of you who keep these answers coming. If you’d like to ask us something, you can go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe! ♪ OUTTRO ♪