Quick answer: Adult bed bugs are flat, oval, wingless insects about 5mm long, roughly the size and shape of an apple seed. They're reddish-brown, and turn darker and more swollen after feeding. Baby bed bugs (nymphs) are smaller and pale, and eggs are tiny, white and about 1mm long. Look for them along mattress seams and bed frames.
Nobody googles what a bed bug looks like out of idle curiosity. You google it holding a phone in one hand and a tissue with something in it in the other, squinting, trying to decide whether it's a bed bug, a crumb or the end of life as you know it.
Here's how to tell them apart at every stage, plus the signs they leave behind. Photo credit for the top image: louento.pix, CC BY-ND 2.0.
What does an adult bed bug look like?
An adult bed bug is about 5mm long, flat and oval, with no wings and six legs. The NHS describes them as dark yellow, red or brown. Before feeding they're flat as a coin. After a meal they swell up, turn darker red and look more like a tiny grape.
That's the cruel part. The well-fed ones are the easiest to spot, because they've been eating you.
| Stage | Size | Colour | What to look for |
|---|---|---|---|
| Egg | About 1mm | Pearly white | Tiny grains stuck in seams and cracks |
| Nymph (baby) | 1.5 to 4.5mm | Pale, almost see-through | Turns red after feeding |
| Adult, unfed | About 5mm | Reddish-brown, flat | Apple-seed shape |
| Adult, fed | Up to 7mm | Dark red, swollen | Rounder and slower |
What do baby bed bugs look like?
Baby bed bugs, called nymphs, are the same shape as adults but smaller and much paler, almost cream or see-through. They're hard to see on white sheets until they've fed, when the blood inside makes them look like a small red dot that moves.
A small red dot that moves is never good news. There's no version of that sentence that ends well.
What do bed bug eggs look like?
Bed bug eggs are about 1mm long, pearly white and slightly curved, like a grain of rice shrunk down. They're laid in clusters in the seams of mattresses, the joints of bed frames and cracks in nearby furniture. You'll usually need a torch to see them.
Signs of bed bugs to look for
Bed bugs hide during the day, so the signs they leave are often easier to find than the bugs themselves. The NHS lists bites on skin left uncovered in bed, spots of blood on your bedding, and small brown spots on bedding or furniture, which are bed bug droppings.
- Bites on the face, neck and arms, often in a line or cluster
- Blood spots on sheets and pillowcases
- Dark brown or black spots along mattress seams
- Pale empty skins shed as the nymphs grow
- A sweet, musty smell in bad infestations
Our bed bug checklist walks through every spot to check, from the headboard to the plug sockets.
What looks like a bed bug but isn't?
A few common insects get mistaken for bed bugs. Carpet beetles are rounder and often patterned. Fleas are smaller, darker and jump.
Booklice are tiny, pale and live on damp paper rather than in beds. Young cockroaches are longer and have long antennae. They also run fast.
| Insect | How to tell it apart |
|---|---|
| Carpet beetle | Round, often mottled brown, white and orange, can fly |
| Flea | Smaller, dark, narrow, jumps |
| Booklouse | About 1mm, pale, found near damp paper |
| Cockroach nymph | Longer body, long antennae, runs fast |
If you're seeing bites but no bugs, our fleas vs bed bugs guide helps you tell the bites apart before you pay for the wrong treatment.
Found one? What to do next
Don't throw the mattress out and don't start sleeping on the sofa. Both tend to spread bed bugs further, and the sofa never forgives you. Put the bug in a sealed bag or take a clear photo, and call a professional to confirm it.
Our bed bug treatment is £220 for the first room and £120 for each extra room, or £450 for heat treatment, with a free revisit if they come back within 60 days. See bed bug treatment in London for what the visit involves.
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Call or WhatsApp 020 7193 0475, or get a free quote online. Bed bug treatment is £220 for the first room and £120 for each extra room. You pay after the treatment, and there's no extra charge for evenings, weekends or bank holidays.
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See how our bed bug treatment in London works, check every price in full, or get a free quote and we will call you back within 15 minutes, day or night. If the pests come back within 60 days, we return free.
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