How Long Can Pubic Lice Live in Bedding? Part of the Answer Is Written in Their DNA

Pubic lice aren’t the most common STI around, but they are definitely one of the strangest. These tiny six-legged crabs, which are some of our species’ oldest companions, really do depend on us for survival. They can, however, occasionally stray away from the human host and hang out in clothing or bedding. Fortunately, they can’t survive that long without us.

One of the most important things to know about pubic lice is that they really do need certain conditions to survive. As Inverse previously reported, the claws of pubic lice are specifically adapted to latch on to thick hair around the genitals, which anchors them to the human host. But that’s not to say that they can’t survive in other locations, specifically in clothing or sheets.

"It’s an issue with clothing and bedding.

The CDC’s estimate for pubic louse survival off of a human host is one to two days. That’s part of what makes the infestation so inconvenient, says Dr. Peter Leone, an expert on pubic lice and infectious disease expert at the University of North Carolina School of Medicine.

“I don’t know what the outer limit is,” Leone tells Inverse. “If someone has pubic lice and they’ve used the sheets, it’s not like after a couple of days you don’t have to worry about it. You might, certainly if they have a lot of infestation, you can get it that way. It’s an issue with clothing and bedding.”

A bed full of pubic lice is a bonafide nightmare, but just because it’s possible doesn’t mean that it’s likely. The entire life cycle of the pubic louse is centered around its attachment to the human host. Pubic lice reproduce by latching onto thick coarse hairs and laying eggs, called nits, on the hair shaft. Once those nits hatch (which takes about six to ten days) they grow into nymphs, and then eventually into full-grown pubic lice with their distinctive claws. Importantly, both nymphs and full-grown pubic lice require blood to survive, which makes bedding a non-hospitable environment for them.

"It’s not like it’s magically going to cross the underwear someone has on and get all over the bedding.

Leone adds that it’s actually fairly hard for pubic lice to end up in bedding in the first place. Pubic lice don’t travel well on foot: As the CDC puts it, “they don’t have feet designed to hold onto or walk on smooth surfaces.” So, to even end up in bedding, pubic lice have to come into direct contact with it and then somehow be forced off of the hairs on human genitals.

“It’s not like it’s magically going to cross the underwear someone has on and get all over the bedding,” Leone explains. “It’s a little bit harder with pubic lice because you’d have to have someone who sleeps in a way that their pubic hair comes in contact with the sheet.”

In short, a pubic louse can’t last long on its own. Ironically, however, this characteristic may have been shaped by one instance where they managed to survive long enough off their initial host to infect another creature. A 2007 paper published in BMC Biology showed that the DNA of human pubic lice shares a significant amount of material with gorilla pubic lice. Millions of years ago, the authors posit, gorilla pubic lice managed to stray from their hosts long enough to jump ship to human pubes, then became the species that plague us today as they adapted to survive.

In that paper, a team led by Florida Museum of Natural History researcher David Reed, Ph.D., wrote that this switch likely happened because of close contact — but not sexual contact — between humans and gorillas. Parasites, like pubic lice, “switch to unrelated hosts in communally used areas, such as roosting or nesting sites,” they write.

In an ancient world without beds, a “roosting or nesting” site is about as close as you can get to actual sheets. So while human pubic lice can only last a day or two, ancient gorilla pubic lice may have lasted long enough off the host to spawn the human variety of pubic lice we know today.

But outside of those hearty gorilla pubic lice than managed to infect ancient humans and give rise to our own unique species of pubic lice, crabs really don’t fare well off of the host. Yes, they can survive, but fortunately, it’s fairly easy to get rid of them once they end up there. Leone recommends washing sheets, towels or clothing in hot water with detergent, which should finish them off for good.