What Causes Bed Bugs? Where They Come From and How to Keep Them Out

What Causes Bed Bugs?

Bed bugs are caused by bed bugs being carried into your home: they hitchhike on luggage, clothing, used furniture and people, or crawl in from a neighbouring unit. The University of Kentucky calls them "efficient hitchhikers" that are easily transported on luggage, and Health Canada notes that they are easily moved from room to room on infested objects. Every infestation starts with an introduction, so the real question is not "why me?" but "how did they get in?"

Do Bed Bugs Come From Dirt?

Bed bugs do not come from dirt. They feed only on blood, so crumbs, dust and dirty dishes give them nothing to eat. According to the University of Kentucky, "unlike cockroaches and flies that feed on filth, there is often no relationship between bed bugs and cleanliness." A spotless condo can get bed bugs as easily as a messy one.

Clutter does matter in one way: it gives bed bugs more places to hide and makes them harder to find and treat. For the full story, read our guide on whether you can get bed bugs if your house is clean.

Can Bed Bugs Come From Outside?

Bed bugs do not come from your yard or garden. They are found worldwide in association with human homes (UC IPM), living close to the people they feed on.

There is one exception that looks the same: bat bugs and bird bugs. These close relatives of bed bugs live on roosting bats or nesting birds such as swallows, and they can wander into living spaces and bite people, especially when their wild hosts leave. According to Colorado State University, they cannot reproduce on human blood, and the fix is usually keeping the bats or birds out of the building. If you have bats in the attic or swallow nests on the house, mention it to whoever inspects your bugs.

What Attracts Bed Bugs to People?

Bed bugs are attracted to people by the carbon dioxide you exhale, your body odours and your body heat. Health Canada notes that bed bugs come out at night to feed, attracted by the carbon dioxide people breathe out. Research published in the Journal of Experimental Biology found that carbon dioxide and body odours seem to work as long-range cues, while heat may only guide bed bugs over the last few centimetres (under 3 cm).

That is why bed bugs settle near beds and couches. UC IPM reports that their hiding places are typically within 6 feet (about 2 metres) of where people sleep or rest. They will also feed on pets, according to Health Canada, but people are what keep them in your bedroom.

Why Are Bed Bugs More Common Now?

Bed bugs are more common now because more people and goods move around, and because the insecticides that once controlled them work less well. UC IPM links the resurgence to increased global travel and commerce, the ease of moving infested items, and widespread insecticide resistance. Nova Scotia's 811 health service adds that older pesticides have been replaced with milder ones that do not harm bed bugs, which has let the population in Canada grow. Experts also admit the reasons are not fully understood.

Where Do Bed Bugs Come From?

Bed bugs come from places where many people sleep or sit, and from belongings that spent time in those places. Here are the most common causes of bed bugs, roughly in order of how often authorities mention them.

Travel Accommodations

Travel accommodations are a leading source. UC IPM lists hotels, shelters, furnished apartments and dormitories as the places most at risk, and HealthLink BC adds student residences. The problem is turnover: every new guest can bring bed bugs in or carry them out. The bugs crawl into suitcases, backpacks and clothing left on or near the bed, then unpack with you at home.

Second-Hand Furniture

Second-hand furniture is one of the highest-risk sources. UC IPM calls second-hand mattresses and furniture "known to be high-risk sources" of bed bug infestations, especially beds, couches and upholstered chairs with seams and joints to hide in. Health Canada's advice is blunt: never take a mattress or sofa from the curb. HealthLink BC adds that you should not rely only on the word of the seller at a second-hand store or garage sale. Check the item yourself.

Used Mattresses

Used mattresses can reach your home even when you buy new. Health Canada advises insisting that a new mattress be sealed before it is delivered, because delivery trucks may also carry old mattresses taken from other homes. Check the new mattress before it comes inside.

Second-Hand Clothing

Second-hand clothing can carry bed bugs or eggs in seams and folds. Nova Scotia's 811 service suggests bringing used clothes home in plastic bags and washing them right away in hot water. Used books and electronics are mentioned by pest control companies as possible hiding spots too, and HealthLink BC notes that bed bugs can hitch rides on books.

Neighbouring Units

Neighbouring units are a common cause in apartments, condos and row houses. The University of Kentucky notes that bed bugs can crawl from room to room, or floor to floor, through cracks and openings in walls, and pest control companies also name wall voids, electrical outlets and plumbing gaps. That is why Health Canada recommends checking entry points on walls you share with neighbours. Learn more about bed bugs in apartments and what to do if bed bugs come from your neighbours.

Visitors

Visitors can bring bed bugs without knowing it. A friend or relative who has bed bugs at home can carry them on clothing, bags or coats, and Canadian pest control companies list visitors among the usual sources. Overnight guests who sleep in your bed or on your couch carry the most risk.

Public Transit

Public transit is a less common source, but it happens. UC IPM notes that people occasionally pick up bed bugs in theatres or on buses and trains. Bed bugs are also carried into offices, hospitals and other workplaces in purses and laptop bags, then go home with someone else.

Shared Laundry Rooms

Shared laundry rooms and laundromats can pass bed bugs from one person's clothes to another's. Health Canada suggests using light-coloured plastic baskets instead of cloth bags, not setting your basket on the floor or near seating, and checking chairs before you sit down. Folding your laundry at home is the safest option.

Moving Day

Moving day mixes your belongings with trucks, boxes and other people's furniture. Health Canada recommends checking items before you put them in your vehicle, and checking your vehicle after helping a friend move. Our guide on how to avoid bringing bed bugs when moving covers the full checklist.

What Turns a Few Bed Bugs Into an Infestation?

A few bed bugs turn into an infestation when they go unnoticed long enough to breed. A handful of hitchhikers is easy to miss, and the conditions below help them settle in.

Fast Egg Laying

Fast egg laying is what makes a small problem grow. According to Health Canada, a female lays at least 200 eggs in her lifetime, at a rate of about two to four a day, and the eggs usually hatch in 6 to 17 days. The eggs are white and about 1 mm long, almost impossible to see on most surfaces. Bed bugs can also live from several weeks to up to a year and a half without feeding, so they can wait out a trip or an empty room.

Late Detection

Late detection gives bed bugs time to multiply. Health Canada explains that bites may not be noticed right away because bed bugs feed at night while people sleep, and most people have only a mild reaction or none at all. By the time you see spots on the sheets, they may have been there for weeks. Learn the signs of a bed bug infestation so you can catch them early.

Clutter

Clutter makes bed bugs harder to find and harder to treat. Piles of clothes, boxes and papers near the bed can give them many more places to hide, which is why Nova Scotia's 811 service and UC IPM both recommend keeping bedrooms free of clutter. See where bed bugs hide for the spots to check.

Bug Bombs

Bug bombs often fail because bed bugs hide deep in seams and cracks the fog cannot reach. An Ohio State University study of 3 over-the-counter foggers found they had little to no effect on bed bugs, and UC IPM reports that some populations are resistant to pyrethroid insecticides. Using one gives the infestation more time to grow. If you want to compare products, see our tests of the best bed bug sprays, and always use only products registered by Health Canada, as directed on the label.

Moving Infested Items

Moving infested items around the home spreads bed bugs to new rooms. Carrying a mattress, cushions or a laundry pile into another room, or sleeping on the couch to escape bites, can take bed bugs with you. Our guide on how bed bugs spread explains how fast this happens.

How Can You Tell Where Your Bed Bugs Came From?

Tracing where your bed bugs came from starts with what changed in the weeks before you noticed them. You will not always find a clear answer, but these clues usually point to the source.

After a Trip

A recent trip is the most likely source if bites or bugs appeared soon after you came home, especially if your suitcase sat on the bed or on the floor of the room. Check your luggage seams and the clothes you packed.

After a New Purchase

A new purchase is a likely source if the first signs appeared on or near something you recently brought in: a used couch, a second-hand bed frame, a mattress delivery or a bag of thrift store clothes. Look closely at the seams, joints and underside of that item.

Without Any Trip or Purchase

Bed bugs that appear without any trip or purchase often come from next door, from a visitor or from a workplace. In an apartment building, signs that start along a shared wall or near outlets suggest a neighbouring unit. If you rent, tell your landlord or property manager right away so neighbouring units can be checked too.

How Do You Stop the Common Causes of Bed Bugs?

Stopping the common causes of bed bugs means checking what comes in: your luggage after a trip, every second-hand item and the gaps you share with neighbours. These steps follow Health Canada's advice.

Travel Checks

Travel checks start before you unpack. Health Canada recommends inspecting the room before bringing luggage in, lifting each mattress corner to check the mattress, box spring, headboard and bed frame, and using a flashlight in the closet. Keep your luggage on the luggage stand or a tile floor, never on the bed. If you see signs, ask for another room that is not next to the first one, or stay elsewhere.

Returning Home

Returning home is your second chance to stop bed bugs. Before bringing your luggage inside, check it on a hard surface. Wash all clothing and fabric items in hot water, whether you wore them or not, and dry items that cannot be washed on the highest heat for about 30 minutes (Health Canada). Vacuum the suitcase, then seal and throw out the vacuum bag. UC IPM suggests storing luggage away from the bedroom, in the garage or a hall closet.

Inspecting Used Items

Inspecting used items before they come inside is the best defence against second-hand bed bugs. Health Canada recommends checking items you bring into your home for the first time. Look along seams, under cushions, inside joints and under the frame of furniture, and wash second-hand clothes right away in hot water. If you cannot inspect it properly, leave it.

Sealing Shared Walls

Sealing shared walls closes the paths bed bugs use between units. Health Canada and HealthLink BC suggest sealing cracks and crevices in baseboards, walls and bed frames, and checking openings around pipes and wires on walls you share with neighbours. HealthLink BC also suggests tightening loose electrical faceplates and repairing loose wallpaper.

Regular Checks

Regular checks catch bed bugs before they become an infestation. Health Canada states that regular inspection is important to prevent infestations. Vacuum often, including under and behind beds, get rid of clutter, and check mattress seams when you change the sheets. Our guide on how to prevent bed bugs gives a complete routine.

When to Call a Licensed Professional

Calling a licensed professional makes sense as soon as you find live bed bugs, eggs or dark spots in more than one place, or when bites continue after you have cleaned and laundered everything. Health Canada strongly recommends hiring a licensed pest control professional, who can find hiding spots you would miss. You can get a quote from a recommended local exterminator through Pest Agent's referral form.