Silverfish in Autumn: What That Damp Corner Is Telling You

You get up in the night, put the bathroom light on, and something small and silver darts for the gap under the skirting. It's fast, it's oddly prehistoric-looking, and it's gone before you've decided how you feel about it. Silverfish are one of the least harmful things we get called about. They're also one of the most useful, because of what they tell you about your building.

The good news first

They don't bite. They are not known to transmit disease to people. They won't damage the structure of your house. In terms of direct harm, silverfish are close to the bottom of the list, and if you've spent the last hour convinced you have a serious infestation on your hands, you can breathe out.

What they will do is eat starches: paper, book bindings, wallpaper paste, cardboard, some fabrics. If you're storing documents, photographs or anything paper in a damp garage or cellar, that's where the actual cost shows up.

Why they're really there

This is the part worth your attention. Common silverfish favour humid conditions. They thrive in damp, dark, undisturbed places, which is why you find them in bathrooms, kitchens, cellars, utility rooms and behind boxes in the garage. They don't create damp conditions, they locate them.

So a silverfish is essentially a moisture detector with legs. If you're seeing them repeatedly in the same spot, something in that spot is wetter than it should be: a slow leak under the sink, poor ventilation in a bathroom, condensation building behind furniture on a cold external wall, a blocked airbrick. They may become more noticeable in autumn where heating, condensation and reduced ventilation leave particular corners humid, but they can remain active indoors throughout the year.

What to do, mostly without us

We'd be doing you a disservice if we sold you a treatment and left the damp in place, because they'll be back. Reducing excess moisture and removing harbourage often substantially reduces silverfish activity.

Run the extractor fan for longer than feels necessary after a shower, and check it's actually shifting air. Open windows briefly even in cold weather. Fix the dripping trap you've been meaning to look at. Pull furniture a few centimetres off external walls so air can move. Get paper and cardboard off cellar and garage floors and into sealed plastic boxes, which protects your belongings and removes their food at the same time. Clear the gaps and cracks where they shelter.

When to call us

If you've dealt with the damp and they're still appearing in numbers, if they're in a commercial premises where they're getting into stock or paperwork, or if you simply can't find the moisture source, that's a reasonable call to make. Treatment is straightforward and targets the harbourage points rather than chasing individuals across the floor. Our silverfish page has more detail, and our pest control page covers how we work across South and Mid Wales.

Get in touch

Seeing them night after night despite your best efforts? Get in touch and we'll sort the insects, and tell you honestly where the damp is coming from.