Silverfish: Identification and Causes

Silverfish (Lepisma saccharinum) are small, silvery, wingless insects that dart away when you switch on the bathroom light. They are harmless to people, but they feed on paper, wallpaper paste and fabrics, and a lot of silverfish is usually a sign that a room is too damp.

How to Identify Silverfish

• A flattened, carrot-shaped body that tapers from head to tail, covered in fine silvery scales.
• Two long antennae at the front and three long bristles at the back.
• A fast, wriggling movement that looks like a fish swimming.
• Active at night. During the day they hide in cracks, behind skirting boards and under baths.

A close relative, the grey silverfish or paperfish, is becoming more common in UK homes. It is larger and duller and copes with drier rooms, so it turns up in bedrooms, living rooms and newer buildings.

How Did I Get Silverfish?

Silverfish need moisture. They are found in bathrooms, kitchens, utility rooms, basements and anywhere with condensation, a leak or poor ventilation. They can be carried in with cardboard boxes, books and old furniture, and they move between flats along pipe runs. They eat starchy materials: paper, book bindings, wallpaper paste, cereals, cotton and linen, as well as mould and dead insects.

Are Silverfish Harmful?

Silverfish do not bite, sting or spread disease. The harm is to belongings. In large numbers they graze the surface of paper and fabric, leaving irregular holes, yellow stains and scraped patches on books, photographs, documents, wallpaper and stored clothes. Their shed scales and droppings, which look like black pepper, can also trigger allergies in some people.

How to Prevent and Get Rid of Silverfish

• Reduce humidity: use extractor fans, open windows after bathing and cooking, and consider a dehumidifier in problem rooms.
• Fix leaks and dripping taps, and deal with condensation and mould.
• Seal cracks around skirting boards, pipes, tiles and bath panels.
• Store paper and fabrics in dry rooms, in sealed plastic boxes, not cardboard.
• Vacuum regularly, including along edges and inside cupboards.
• Keep dry food in airtight containers.

If you still see silverfish regularly after dealing with the damp, the population is well established and a professional treatment will clear it.

Frequently Asked Questions

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