How do I keep house centipedes out of the bathroom?

House centipedes are the fast ones with long legs all round the body. They are hunters. They come for damp air and for the small insects that live in it, like silverfish, spiders and booklice. So one in the bathroom is a clue about damp and food, not about how clean you keep things. To keep them out, do three things: dry the room, close the gaps, and cut their food.

Being creeped out by them is normal. They move fast and seem to come from nowhere. But they do not eat your food, chew your things or damage the house.

Why the bathroom?

The bathroom is often the dampest room in a home, and damp brings the insects centipedes eat. Gaps behind the bath panel, round the waste pipe and under the skirting give them dark places to wait during the day.

You often find one in the bath or sink in the morning. That makes it look as if it came up the drain. Usually it walked in, went over the edge and could not climb back up the smooth sides.

Why peppermint and vinegar did not help

Pouring peppermint oil or vinegar down the drain is a popular tip, and it makes sense that you tried it. It does not keep house centipedes away, for two reasons. They mostly are not coming from the drain. And a smell fades within hours, while the damp and the insects they eat stay put. Put the effort into the steps below instead.

The plan

1. Dry the room. Run the extractor fan during every shower and for a while after. No fan, or a weak one? Open a window. Wipe or squeegee the walls and screen, fix dripping taps, and check for leaks behind the bath and toilet. A small dehumidifier helps in a bathroom without a window.
2. Close gaps at floor level. Seal along the bath panel, round the base of the toilet and basin, round pipes where they go through walls and floors, and along the skirting with a flexible sealant. Fill cracked grout and tiles. See sealing gaps.
3. Close the way in from outside. Door sweeps on outside doors, fine mesh over air bricks and vents, gaps round outside pipes sealed. Keep leaves, wood and debris cleared from the base of the walls, as you have already started doing.
4. Cut their food. Fewer silverfish, spiders and other small insects means fewer reasons to stay. Silverfish follow damp too, so step 1 helps twice. See do silverfish mean my home is dirty?
5. Track with traps. Sticky monitor traps along the bathroom walls show whether centipedes, and the insects they hunt, are dropping off. Check weekly and note the counts. See monitor traps.

If you meet one

Use the same method as for a spider: a clear glass over it, a stiff card slid underneath, and a release outside away from the door. They are quick, so wait until it stops. The full steps are in how to catch a big spider without touching it.

Spraying the one you see does nothing about the next one. Drying and sealing do.

Kids, pets and bites: house centipedes can bite if handled, so do not pick one up, and teach children to leave them alone. Tuck sticky traps behind the bath panel or the washing machine, away from children and pets. If a bite swells badly or someone feels unwell after one, see a pharmacist or doctor.

When to get help

If you have dried and sealed the room and still see them most nights after a month or two, there may be hidden damp: a slow leak under the floor, a wet wall, a damp crawl space or cellar. A plumber or damp specialist will find more than a pest spray will. If you rent, report damp or leaks to your landlord in writing, with dated photos.

If you also see silverfish, booklice or lots of spiders, deal with those first. When the food goes, the centipedes usually follow.