The short answer
A bed bug is a small, wingless, blood-feeding insect — adults run 5 to 7mm, flat and reddish-brown before feeding, swelling and darkening to a deep red after a blood meal. They can't fly or jump, only crawl. During the day they hide in narrow gaps close to where you sleep — the seam along a mattress edge, bed frame joints, sofa cushion gaps — and come out to feed at night. The most reliable way to check is inspecting those gaps directly, not just looking for bites.
- Scientific name
- Cimex lectularius
- Chinese name
- 床蝨
- English name
- Bed bug
How to identify a bed bug
- Size: adults are about 5 to 7mm, flat and oval — visible to the naked eye, no magnifying glass needed.
- Colour: flat and reddish-brown before feeding; swollen and deep red after a blood meal, moving more slowly once fed.
- Can't fly and can't jump — only crawls, which is why every infestation arrives by hitchhiking (luggage, furniture, clothing) or spreading in from a neighbouring flat.
- Nymphs are tiny (around 1mm) and near-translucent, very hard to spot before they've fed.
Where do bed bugs hide in a Hong Kong home?
Bed bugs stick to narrow, dark gaps close to where you sleep and rarely come out during the day:
- The seam along a mattress edge, and the gap between mattress and frame
- Bed frame joints and behind the headboard
- Sofa cushion seams and armrest gaps
- Carpet edges near the bed, behind wall sockets (in more advanced cases)
- Checking tip: look for tiny black spotting and reddish-brown smears — these often show up before you spot a live bug
Why does it matter?
Bed bug bites leave rows of itchy, red welts, and the most direct impact is on sleep quality and stress — most people find an active infestation genuinely unsettling. Bed bugs are not a known disease-transmitting insect, but because they hide deep and breed quickly, the longer treatment is delayed, the further they spread and the more it costs to clear.
Does spraying insecticide yourself work?
Because bed bugs hide deep and their eggs are protected, contact spray often just scatters them — turning a single-room problem into a multi-room one. Professional treatment generally uses heat treatment or residual insecticide, combined with gap-by-gap inspection and a follow-up check. For how bed bugs get in and how to block each route, see our how bed bugs spread guide; for telling bites apart, see our bite comparison guide.
How to keep them from coming back
- Inspect every seam of second-hand furniture, especially sofas and bed frames, before bringing it in
- After a trip, keep luggage off the bed and hot-wash or steam-treat your clothing
- If a nearby flat has a known case, check your own home early
- Check early if you spot bites or black spotting — don't wait for a full row of bites before acting