It bites and feeds on blood, and it is not known to transmit disease to people. The real costs are the reaction to the bites, the sleep, and how hard an established infestation is to remove.
We identify, we don't diagnose. If you've been bitten or stung and symptoms develop, or you're worried, seek medical attention.
Size4–5 mm as an adult; nymphs from about 1 mm
MarkingsFlat and oval before feeding, swollen and reddish after — like an apple seed · Adult 4–5 mm, reddish-brown, with no functional wings
WhereWithin a few feet of where people sleep — mattress seams, bed frames, headboards, bedside furniture and skirting behind the bed.
What it is not
A bed bug is most often confused with a species that is medically significant. If you are trying to rule those out, check these:
Flat and oval before feeding, swollen and reddish after — like an apple seed
Adult 4–5 mm, reddish-brown, with no functional wings
Six legs, which separates it from a tick's eight
Dark smear marks along mattress seams and headboard joints
Pale translucent nymphs and shed skins in the same places
Where you’ll find it
Everywhere in the United States. Prevalence tracks travel and density, not cleanliness.
Within a few feet of where people sleep — mattress seams, bed frames, headboards, bedside furniture and skirting behind the bed.
How it behaves
It feeds at night, for a few minutes, and spends the rest of its time hidden in a tight crack close to the bed. That is why the insect is found by looking at the harbourage rather than by waiting to catch one — and why the evidence people find first is usually smears, shed skins and eggs rather than a live bug. They can survive months without feeding, which is why leaving a room empty does not solve it, and they travel in luggage and second-hand furniture rather than walking between buildings.
What a bite looks like
Small red raised marks, often in a line or a loose cluster, on skin exposed while sleeping. Reactions vary enormously — some people show nothing at all.
Painless at the time. Itching develops over hours to days, and the delay is why people rarely connect the bite to the night it happened.
We identify, we don't diagnose. Bites themselves usually need nothing beyond not scratching. See a doctor if a bite becomes infected, or for any widespread or severe reaction.
A skin mark cannot confirm which animal caused it. Read the bug bite and sting guide for the limits and the symptoms that should end an online search.
You’ve found one indoors
Confirm before treating: strip the bed and check the seams, the piping, the frame joints and the underside of the headboard for dark smears and shed skins. Do not throw the mattress out first — that spreads it. This is one of the few things on this site where professional treatment is usually necessary, because partial treatment reliably fails and heat treatment needs equipment.
Common questions
Do bed bugs spread disease?
They are not established as disease vectors to people, which is the main thing that separates them from ticks and fleas. The harm is the bites, the reaction and the difficulty of eradication.
Does having them mean my home is dirty?
No. They travel in luggage and second-hand furniture and feed on people, not on food waste. Clutter makes them harder to eliminate; it does not attract them.
How do I know it is bed bugs and not something else?
Look for the evidence rather than the bites, which are not diagnostic. Dark smears along mattress seams, shed skins and pale eggs in the same cracks are far more reliable.
Is it a tick?
Count the legs. Bed bugs have six, ticks have eight. It matters — a tick carries disease risk and a bed bug does not.
Katja Schulz · CC-BY