Big dark cockroach in the kitchen at night. Should I worry?

A big cockroach is a shock, especially at two in the morning. But size tells you nothing about numbers. Large dark cockroaches are usually American or Oriental cockroaches. They tend to come in from drains, cellars and the garden rather than breed in your cupboards. The small one is usually the bigger worry. With these, the fix is mostly about closing the way in.

Which one was it?

• Large and reddish brown, with a pale band behind the head: likely an American cockroach. Often in from sewers, drains and outside. It may glide or fly short distances in warm weather.
• Dark brown to almost black, shiny and slow: likely an Oriental cockroach. It likes cool, damp places: drains, cellars, under floors, around bins.
• Small and tan, with two dark stripes behind the head: a German cockroach. This is the one that breeds in kitchens, and it needs a different plan.

Our four cockroaches side by side shows the tell for each. A young German cockroach is small and dark, so do not judge on colour alone.

Where they get in

Big cockroaches use the plumbing and the gaps around it. A sink or bath plug left out, a floor drain that has dried out, a gap where a pipe goes through the wall, the space under a back door. Seeing them in sinks and toilets in a new flat usually points to the drains.

They are mostly night visitors. But they can settle in warm, damp spots like cellars, boiler cupboards and the space under the floor. That is why you check, rather than assume.

The plan

1. Close the way in. Put plugs in sinks and baths at night. Pour water into drains you rarely use, so the water in the U-bend stays topped up. Fit covers on floor drains, seal gaps around pipes and fit a door sweep. See sealing gaps.
2. Dry the damp spots. Fix leaks under the sink, wipe up condensation, do not leave wet mops and cloths out overnight.
3. Take away food. Lids on bins, no pet food out overnight, crumbs swept from behind the cooker.
4. Bait near the entry points. Bait stations or gel bait under the sink, beside drains and by the back door. Follow the label and check the product is allowed where you live.
5. Count. Put monitor traps by the drains, under the sink and along the kitchen wall. Check weekly. A few big adults now and then point to visitors. Lots of young ones point to a group living close by.

Spraying the one you see is fine to stop that one. It will not stop the next one, because the next one comes from the same drain. Our page on cockroaches coming up the drain goes further, including why bleach down the plughole does not solve it.

Kids and pets: bait beside floor drains and back doors sits at exactly the height of toddlers and pets. Use closed bait stations, tuck them behind appliances and in the cupboard under the sink, out of children’s and pets’ reach, and follow the label.

Can they make you ill?

Cockroaches walk through drains and bins, so they can carry germs onto worktops and food. Their droppings and shed skins can also trigger allergies and asthma in some people. Keep food covered, wipe worktops before you cook, and throw away anything you think one has walked on. If you feel unwell, or your breathing has got worse, see a doctor or pharmacist. Our page on cockroaches, asthma and health has more.

Moving out soon?

It is still worth doing the plan. Most of it is free, and a few months is a long time to share a kitchen at night. If you rent, tell your landlord in writing now, with the dates you saw them. That protects you when the deposit comes up. And before you pack, read our page on moving without bringing cockroaches.