Do silverfish mean my home is dirty?

Silverfish live in spotless flats, new builds and old houses alike, wherever the air is humid and there are cracks to hide in. They do not bite, and they are not known to spread disease. Finding one on a towel is horrible, but it says more about the bathroom’s air than about you.

The fix is mostly drying and sealing. Spraying alone rarely holds while the damp stays, which is why some people pay for treatment and see them again a few weeks later.

Where silverfish come from

They like humid, still air and somewhere tight and dark: behind bath panels, under skirting, in a cupboard with a hot water tank, behind kitchen units, inside stacks of paper and cardboard. At night they come out to feed on starchy things like paper, glue, crumbs, dust and mould.

They do not build nests. People picture a nest you could find and take away, but silverfish spread out through lots of small cracks near the damp. That is why drying and sealing work better than hunting for one source.

They can climb, so one on the hob or in a high cupboard does not mean it lives there. It is wandering from somewhere damp nearby.

Is a few a lot?

• One or two now and then near a bathroom or kitchen is common in many homes.
• A few in a bedroom after new furniture arrives: they may have come in with it, or the move disturbed ones already behind the old pieces. Put out traps and see whether it keeps happening.
• Many every night, in several rooms, or small pale young ones as well as adults: something damp is feeding them. Go looking for it.

The plan: dry, seal, track

1. Dry the air. Run the extractor fan during showers and for a while after, open a window, wipe down the bath and tiles, and dry washing outdoors or in a vented dryer when you can. A dehumidifier helps in a bathroom or a cupboard with a water tank.
2. Fix the water. Look for a dripping tap, a leaking pipe under the sink, or condensation on a cold pipe. Silverfish crowd round a slow leak.
3. Seal the cracks. Run a bead of sealant along gaps round the bath, basin, skirting and pipes. Fewer cracks, fewer places to live. See sealing gaps.
4. Get paper off the floor. Store paper, books and cardboard in plastic boxes with lids, off the floor and away from outside walls. Swap cardboard boxes in lofts and cupboards for plastic ones.
5. Track with monitor traps. Set sticky traps along the skirting in the bathroom, kitchen and any room you see them. Check weekly and write the count down. Falling counts mean the drying is working. See monitor traps.

Babies, kids and pets: silverfish do not bite, so a towel one ran across only needs a normal wash. Tuck sticky traps behind the toilet or under the bath panel, out of reach of children and pets. If anyone treats with a dust or spray, follow the label and keep children and pets out of the treated area for as long as it says.

During a kitchen refit

When the old units come out, you will probably see more for a few days, because their hiding places have gone. Expect it, and use it as a chance to fix the problem at its source.

• Vacuum the floor and wall behind the old units and empty the vacuum outside.
• Check for leaks and damp patches while the wall is bare, and let it dry before anything goes back.
• Seal gaps round pipes and along the base of the wall before the new units go in.
• Keep monitor traps out for a few weeks after the new kitchen is fitted.

Renting, and when to get help

If you rent and the damp comes from the building, such as a leak, a broken extractor fan or condensation that airing cannot clear, tell your landlord in writing with dated photos and your trap counts. How to document pests for your landlord covers what to send.

Call a professional if counts stay high for a month or two after you have dried and sealed. Ask what they will do about the damp, not only what they will spray. A good pest controller treats the cracks and helps you find where the moisture comes from.

Seeing much smaller pale bugs on books and window sills instead? They may be booklice, which also follow damp. See what are these tiny white bugs?