The world is full of insects who are out for our blood. Since the dawn of human existence, we’ve been snacked on by ticks, lice, fleas, flies and mosquitoes beyond counting. But in recent times, few parasitic insects have instilled more skin-crawling revulsion — or fear of infestation — than the common bed bug.

And with good reason: According to the U.S. Environmental Protection Agency, cases of bed bug infestation have been increasing over the past 20 years. As many as 1 in 5 Americans either knows somebody who has dealt with bed bugs in a hotel or home, or has suffered an infestation themselves, according to statistics from the National Pest Management Association. And once you have bed bugs in your house, it can be a frustrating, time-consuming and sometimes expensive process to vanquish them completely.

But bed bugs can be beaten. As with so many pests, knowledge is your greatest weapon, and we’re just itching to share it. Here’s what you need to know.

Where Do Bed Bugs Come From?

Bed bugs have been around since before beds existed — since before humans existed, in fact. While evidence of human contact with the parasite goes back around 5,000-11,000 years, researchers have discovered bed bug ancestors dating to as early as 100 million years ago.

At some point through the long eons of history, bed bugs (or Cimex lectularius, as scientists have named them) eventually added us to their diet — bats are commonly pointed to as the creature that exposed humans to the bloodthirsty insect. We’ve been trying not to let the bed bugs bite ever since.

Read More: Horrifying Study Shows How Far Bed Bugs Can Spread

How Do You Get Bed Bugs?

Part of the reason that they can be so pervasive is the simple fact that bed bugs don’t just live in beds: They are surprisingly hardy and adaptable to a range of environments. Of course, nursing homes, hotels, cruise ships, hospitals and college dormitories are all obvious potential habitats, but bed bugs are frequently found in other places, including offices, schools — even planes, trains and buses. Almost anywhere that humans hang out can be a possible vector for infestation.

Experts have also noted a general uptick in infestations after the COVID pandemic, attributed to both an increase in travel and a decrease in professional housekeeping services, especially at hotels — sheets that haven’t been properly laundered and bedrooms that haven’t been fully cleaned are a prime breeding ground for bed bugs, which all too often feast on guests and then hitch a ride home with them.

That’s not to say that bed bug habitats have to be dirty. While evidence suggests the bugs can gravitate towards dirty laundry or cluttered spaces with lots of areas to hide, the neatest, cleanest homes and buildings can get bed bugs just the same as any filthy or unwashed locale. Bed bugs don’t care so much about cleanliness or lack thereof; they are mainly attracted to warmth and blood. So, if you happen to sit or sleep in a place where bed bugs have been able to thrive, you’re a target.

Read More: Why Are We Afraid of Bugs?

How Are Bed Bugs Spread?

To be more accurate: you’re a vehicle. Unlike some parasitic creatures, bed bugs don’t live on your body. They’ll attach themselves to you long enough to feed, but once they have their blood meal, bed bugs retreat to their habitat. In addition to beds, bed bugs can live in furniture, curtains, carpets, even inside walls and baseboards too.

Once they hatch and start feeding, they can quickly grow and propagate. It only takes about a month for a female bed bug to mature enough to lay eggs of her own — and a single bed bug can lay as many as six or seven eggs per day, depending on how long she’s lived and when her last blood meal was.

Read More: Human History, As Told by Parasites

What Do Bed Bugs Look Like?

Given their growing notoriety over the years, you’d think all of us would have a pretty good idea of what bed bugs look like by now, but in fact bed bugs are sometimes confused with other insects and vice versa.

For the record, bed bugs have flat, oval bodies, which make them look a bit like small cockroaches or beetles — and by small we mean no bigger than 1/4 inch long. The common comparison made is that the bugs are about the size of an apple seed. They’re usually brown or rusty red if they’ve fed recently. Younger bugs, known as nymphs, are smaller and harder to see as they are light-colored and often translucent. Bed bug eggs are the smallest of all — you can fit one on the head of a pin. Like nymphs, they are very light-colored, which can make them hard to spot. 

Read More: Do Insects Have Feelings and Consciousness?

How to Check for Bed Bugs

Once you know what bed bugs and their eggs look like, checking for them is a simpler matter, although it may still take some time and patience. Early signs of bed bugs will include bites, of course. Bed bug bites can sometimes be confused with other insect bites, such as fleas or mosquitos. But mosquito bites, and the welts that rise from them, tend to be bigger, lighter in color, and more immediately obvious. When it comes to bed bug bites vs. flea bites, bear in mind that flea bites tend to show up as small, red bumps, scattered randomly on the skin. They also tend to appear around skin folds and on the lower part of the body.

Bed bug bites, meanwhile, are more likely to appear on your upper body, including your face and neck. Bites also tend to be less random, and in more of a linear or zig-zag pattern. The bites may at first show up as small, red, itchy welts, but will usually develop a little pustule or blister with a pinprick of blood visible) in a day or so.

From there it’s a matter of carefully inspecting the rooms and furniture where you spend your time. In addition to the obvious — examining sheets, pillows, mattresses, cushions, curtains and so on — be sure to look in all cracks and crevices of beds and other furniture. Have a flashlight handy. A magnifying glass wouldn’t hurt, either: While bed bugs are visible to the naked eye, the smallest nymphs and eggs may be tough to spot.

In addition to the bugs and eggs themselves, keep an eye out for small rusty-red stains (remnants of dead and crushed bugs) or tiny black dots (bed-bug droppings) on linens or other surfaces that you suspect may be harboring the critters.

Read More: 450,000 Americans May Have A Meat Allergy Caused By Tick Bites

Are Bed Bug Bites Dangerous?

For most people, bed bug bites are certainly irritating, but not life-threatening. You can treat the itching and minor swelling with an over-the-counter hydrocortisone cream or an oral antihistamine. Most bites tend to go away on their own in about two weeks, depending on how sensitive your skin is to insect bites. Be careful not to scratch too much to avoid injuring your skin and causing an infection. If the itching or swelling only worsens over several days, check with your doctor to see if you need a prescription steroid or (if an infection is present) antibiotic.

In rare instances, some people can have allergic reactions to a bed bug bite, which could include excessive itching and a hive-like rash. In extreme cases, very sensitive bed bug victims could suffer a severe reaction that includes dangerous swelling and difficulty breathing — such cases could be deadly, and require immediate medical attention.

Read More: How to Avoid This Common Misdiagnosis: What A Brown Recluse Bite Looks Like

How to Get Rid of Bed Bugs Fast

While you can eliminate a bed-bug infestation on your own, the fastest, most effective method to wipe them out may simply be to call in a professional pest control service; these days they have plenty of experience dealing with bed bugs. Depending on how severely your home is infested, a minor treatment could cost only a few hundred dollars and take a matter of hours. However, for a serious case, a more thorough extermination may be required, necessitating multiple treatments over a few weeks, with typical costs running from $1,750 to $2,000, sometimes more.

If you can’t afford that expense, you can wipe out bed bugs on your own, but it will take a lot more time and some painstaking work on your part. It may also require products like bed-bug traps or interceptors, many of which are pesticide-free. Home-improvement stores also sell bed-bug foggers, which do contain chemicals that may be harmful to people. They also won’t necessarily eliminate the problem, as bed bugs have become more resistant over time to the active ingredients in some foggers.

High heat is the bed bug’s Kryptonite, though, so one of the most effective things you can do boils down — not quite literally — to washing affected linens and clothing in very hot water (anything over 122 degrees Fahrenheit), drying those items in very high heat, and cleaning and disinfecting rooms and sometimes whole houses. 

For even more guidance, the EPA offers a host of information about identifying and getting rid of bed bugs. Sleep tight! 

Read More: Meet the Parasites that Control Human Brains