Bed bugs feed on human blood, typically at night while you sleep. They inject chemicals through their saliva that numb your skin and prevent your blood from clotting, so you rarely feel the bite as it happens. Beyond feeding, bed bugs reproduce, hide in tight spaces near their hosts, and hitchhike on personal belongings to spread to new locations. They don’t transmit diseases, but their presence causes real physical and psychological harm.
How Bed Bugs Feed
Bed bugs are obligate blood feeders, meaning blood is the only thing they eat at every stage of life. They’re drawn to the carbon dioxide you exhale and your body heat, which is why they tend to bite exposed skin on the face, neck, arms, and hands. Their mouthparts are designed to pierce skin and draw blood through a thin, straw-like tube.
The reason you don’t wake up during a bite comes down to their saliva. It contains both an anesthetic, which numbs the bite site, and an anticoagulant, which keeps your blood flowing freely so the bug can feed without interruption. A single feeding takes about 5 to 10 minutes, after which the bug retreats to its hiding spot to digest. Bed bugs typically feed every 5 to 10 days, though they can go much longer without a meal if no host is available. At cooler temperatures, adults have been documented surviving several months between feedings.
What the Bites Look and Feel Like
Reactions to bed bug bites vary dramatically from person to person. Some people show no visible marks at all, while others develop red, swollen, intensely itchy welts. The bites often appear in clusters of three to five, sometimes in a straight line or zigzag pattern. This grouping happens because a single bug may probe multiple spots before finding a good blood vessel, or because several bugs feed in the same area.
For most people, the bites are an itchy nuisance that fades within a week or two. A smaller number of people have stronger allergic reactions that produce large, painful, swollen marks. In very rare cases, bites can trigger anaphylaxis. The biggest physical risk from bites is actually secondary: scratching the itchy welts can break the skin and invite bacterial infection. Applying antiseptic cream and resisting the urge to scratch is the most effective way to manage bites.
How They Reproduce and Spread
Bed bugs reproduce quickly enough that a single fertilized female can start an entire infestation. After one blood meal, a female lays between 1 and 7 eggs per day for about 10 days. Over her lifetime, she produces roughly 113 eggs. The eggs are tiny, white, and about the size of a pinhead, typically glued into cracks and crevices near where people sleep.
Nymphs (immature bed bugs) must take a blood meal before they can molt to the next stage, and they pass through five stages before reaching adulthood. This entire process from egg to adult takes roughly 5 to 8 weeks under favorable conditions. Because every life stage requires blood, bed bugs stay close to where people rest for extended periods, especially beds, couches, and upholstered chairs.
Bed bugs don’t fly or jump. They crawl, and they spread primarily by hitchhiking on objects. They travel on luggage, furniture, clothing, books, electronics, and even in the textured soles of shoes. This is why infestations commonly follow travel, used furniture purchases, or moves into new housing. They can ride on trains, planes, and cars, making them remarkably efficient at colonizing new spaces despite their limited mobility.
Where They Hide During the Day
Bed bugs are nocturnal and spend most of their time hiding in tight, dark spaces close to their host. Mattress seams, box spring joints, bed frame crevices, and headboard gaps are the most common spots. As infestations grow, they spread outward to nightstands, baseboards, electrical outlets, picture frames, and even behind peeling wallpaper. Their flat bodies allow them to squeeze into cracks as thin as a credit card.
They don’t build nests the way ants or bees do, but they do tend to cluster in groups. You’ll often find live bugs, shed skins, eggs, and dark fecal spots (digested blood) all concentrated in the same hiding area. These clusters are one of the most reliable signs of an infestation, often more obvious than the bites themselves.
Do Bed Bugs Carry Disease?
Bed bugs are not known to spread diseases to people. Despite feeding on blood, they haven’t been shown to transmit pathogens the way mosquitoes or ticks do. The CDC has confirmed this, and it holds true even in heavy infestations. The direct health consequences are limited to the bites themselves and any secondary skin infections from scratching.
The Psychological Toll
What bed bugs do to mental health is often worse than what they do to skin. Research published in The American Journal of Medicine found that bed bug infestations can cause insomnia, anxiety, nightmares, flashbacks, hypervigilance, and avoidance behaviors. These symptoms overlap significantly with post-traumatic stress disorder. In one study evaluating 135 firsthand accounts of infestations, 110 described measurable psychological effects, and one met the clinical threshold for a PTSD diagnosis.
A cross-sectional study published in the British Medical Journal confirmed that people who experienced bed bug exposure had higher levels of sleep disturbances and anxiety compared to those who hadn’t. Separate clinical case reports found that infestations triggered new-onset depression and worsened pre-existing psychiatric conditions. The constant awareness that something is feeding on you while you sleep, combined with the difficulty of eliminating an infestation, creates a cycle of stress that can persist long after the bugs are gone.
Even the fear of bed bugs, without confirmed exposure, has been documented to cause psychiatric symptoms. This makes bed bugs unusual among household pests: their psychological impact often outweighs their physical one.