Household pests
Silverfish: why you have them and how to get rid of them
Silverfish are small, wingless, silvery insects that move with a wriggling, fish-like motion and thrive in damp, humid rooms such as bathrooms and kitchens. They do not bite or spread disease, but they signal excess moisture. Reduce humidity and fix damp, and they usually disappear without professional treatment.
- Also known as
- Lepisma saccharina, fishmoths
- Easily confused with
- firebrats (prefer hot, dry places), carpet beetle larvae, booklice
- How serious
- Low: a nuisance and a damp indicator, not a health risk
- Typical cost
- Usually no cost beyond a dehumidifier and traps; pro treatment, if needed, from around 70 to 150 pounds
How to identify silverfish
Silverfish are 10 to 12mm long, teardrop or carrot shaped, and a metallic silver-grey. They have two long antennae at the front and three bristle-like tails at the back, and they move in a quick, darting, side-to-side wriggle.
You usually see them at night in sinks, baths or basins, where they have fallen in and cannot climb the smooth sides. Other signs are tiny yellowish stains, small holes or grazed patches on paper, wallpaper paste and book bindings, and fine pepper-like droppings.
How serious is it?
Low: a nuisance and a damp indicator, not a health risk
Silverfish are harmless to people. They do not bite, sting or carry disease, and they do not damage the structure of a building.
They are mainly a nuisance and an indicator. They feed on starches and sugars in paper, glue, wallpaper paste and stored food, so large numbers can damage books, documents and packaging. Their real value is as a sign that a room is too humid, which is also what encourages mould.
How to fix it yourself
- Cut the humidity. Use an extractor fan or open a window when bathing or cooking, and run a dehumidifier in persistently damp rooms.
- Fix the moisture source: leaking pipes, condensation on cold walls, and poor ventilation behind units.
- Reduce food and harbourage: store paper, books and dry food in sealed boxes, and clear clutter where they hide.
- Vacuum cracks, skirting and the backs of cupboards, then seal gaps where they travel.
- Use sticky traps to monitor numbers, and a desiccant such as diatomaceous earth or a proprietary trap in problem corners if needed.
When to call a professional
- Numbers keep rising despite reducing humidity and removing food sources.
- You see silverfish across many rooms, which can point to a wider damp or structural moisture problem worth investigating.
Who to call
- A BPCA or NPTA member pest controller for a persistent infestation.
- A damp specialist (for example a Property Care Association member) if the underlying problem is condensation or rising damp rather than the insects themselves.
Indicative cost: Usually no cost beyond a dehumidifier and traps; pro treatment, if needed, from around 70 to 150 pounds. Prices vary by area, severity and access, so always get a written quote.
Frequently asked questions
Are silverfish harmful to humans?
No. Silverfish do not bite, sting or transmit disease to people or pets. They can damage paper, books and stored food, and they indicate a humidity problem, but they are not a health risk.
Why do I suddenly have silverfish?
Silverfish appear when a room becomes damp and humid, often after a leak, poor ventilation, or condensation in a bathroom or kitchen. They are drawn to moisture and to starchy foods such as paper and wallpaper paste.
What instantly kills silverfish?
Contact insecticide sprays and desiccant powders such as diatomaceous earth will kill silverfish they touch, but they will keep coming back unless you reduce the humidity that supports them. Lowering moisture is the only lasting fix.
Do silverfish mean my house is dirty?
Not necessarily. Silverfish are a sign of damp and humidity rather than poor hygiene. Even clean, tidy homes get them if a bathroom or kitchen is poorly ventilated or there is a hidden leak.
Sources
Editor, HomesAndHedge
Oliver leads HomesAndHedge's editorial coverage of home and garden problems. He researches and writes the plain-English explainers on pests, invasive plants, damp and mould, drainage and wildlife, drawing on guidance from bodies such as the Property Care Association, the RHS and the NHS, and is clear about when a job needs a qualified professional.
Last reviewed: 8 June 2026