Silverfish are among the oldest insects on the planet, and they have shared houses with people for just as long. The silvery-gray, wingless insects do not bite, sting, or spread disease, but they are destructive in practice: they feed on starchy materials, and a serious infestation can ruin books, wallpaper, cardboard boxes, and clothing. Adults live two to eight years, and females lay eggs continuously through adult life, so a small population can grow into a persistent problem with no obvious warning. The insects slip through gaps that look too small to matter, which is why they show up in newly built homes as easily as in older houses. Knowing what draws them in is the first step to keeping them out.
Why Silverfish Enter Your Home
Silverfish do not march through the front door in daylight. They enter through the same gaps that let in drafts, moisture, and other pests, and they stay where conditions suit them. Pest control technicians point to five recurring entry routes.
Five Entry Routes
- Humidity. Silverfish thrive where relative humidity stays above 75 percent, which makes bathrooms, basements, and laundry rooms their favorite rooms. A dehumidifier set to 45 to 50 percent makes those spaces far less inviting.
- Cracks in the foundation. Settlement cracks and gaps around pipes give the insects a direct path from the soil and crawlspace into living areas.
- Gaps around windows and doors. Unsealed window frames, worn weatherstripping, and missing door sweeps are open doors to a silverfish. Their bodies are thin and flat, so they only need a crack a few millimeters wide.
- Vents and utility penetrations. Attic vents, dryer vents, and holes drilled for cables or plumbing are common, forgotten entry points.
- Construction and deliveries. In newer homes, the insects can crawl in during framing and get sealed inside when the walls are finished. They also ride into the house inside cardboard boxes and grocery bags.
Moisture is the strongest attractant of the five. Silverfish lose water quickly through their exoskeletons, so they avoid dry rooms and concentrate wherever pipes leak, showers steam, or foundations stay damp. Measuring humidity with a cheap hygrometer tells you which rooms need the dehumidifier first, and the same fixes that stop drafts also stop silverfish: caulk the gaps, replace the weatherstripping, and add a door sweep, and most of the routes close in a single afternoon.
What Silverfish Eat and Where They Hide
Silverfish are built around one food source: carbohydrates in the form of starch and cellulose. They can digest the glue in book bindings, the sizing in paper, the paste in wallpaper, and the fibers in cotton and linen. In practical terms, the pantry, the bookshelf, and basement storage are all on the menu, along with dried pet food, cereal, flour, and even the adhesive on envelope flaps.
Favorite Hiding Spots
- Basements and crawlspaces, especially near cardboard boxes
- Bathrooms, behind the toilet and under the sink
- Closets holding paper, photo albums, or fabric
- Attics, where insulation and stored items hold heat and moisture
- Behind baseboards, window trim, and built-in shelving
The starchy diet explains the damage pattern. Books get eaten at the spine where the glue sits, wallpaper shows irregular grazing lines, and clothing develops small holes at collars and cuffs where starch sizing concentrates. Fabrics made from cotton and linen are at risk; synthetics usually survive unless they carry a starch finish.
People often confuse silverfish with the house centipede, which looks similar at a glance but moves much faster and hunts silverfish rather than eating paper. Telling the two apart matters, because a house centipede is a predator worth keeping around, while silverfish are the pest itself.
Because silverfish hide in dark corners and come out at night, most infestations are discovered by accident: a book pulled from a shelf, a box moved in the garage, or a bathroom visit with the light on.
Signs of a Silverfish Infestation
You rarely see the insects themselves first. What you notice is the damage and the droppings they leave behind.
What the Damage Looks Like
- Yellowish stains on paper, books, or clothing, left by feeding and digestive secretions
- Small pepper-like specks that are their droppings
- Irregular holes in paper, wallpaper, or fabric
- Tiny silvery scales shed as the insects grow
- Shed skins in drawers, boxes, and behind furniture
Yellowing on paper is the easiest sign to miss because it looks like age. The difference: silverfish staining appears as irregular blotches near the edges of the item, where the insects could reach it, rather than a uniform fade across the whole page.
Check the usual harborage spots once a month: under the kitchen sink, behind the toilet, in the back of closets, and inside any box that has sat undisturbed for more than a season. Silverfish do not discriminate between a cluttered basement and a tidy house; they appear in rentals, family homes, and showcase homes whenever humidity and food sources line up.
How to Get Rid of Silverfish
Removal works best as a layered approach: cut the moisture, remove the food, seal the entry points, and treat the hiding spots. No single product handles all four, which is why one-shot sprays usually fail. Start with the non-chemical steps and add dusts or traps only where the insects actually travel.
Control Methods Compared
| Method | How it works | Where to use it |
|---|---|---|
| Dehumidifier | Lowers humidity below the 75 percent threshold silverfish need | Basements, bathrooms, crawlspaces |
| Caulk and weatherstripping | Seals the cracks and gaps they travel through | Baseboards, window frames, pipe penetrations |
| Diatomaceous earth | Abrasive dust that damages the exoskeleton so insects dry out | Along baseboards, behind appliances, in wall voids |
| Boric acid dust | Slow-acting stomach poison insects carry back to the harborage | Cracks and behind fixtures, out of reach of pets |
| Sticky traps | Monitors and reduces small populations | Under sinks, in closets, along baseboards |
| Professional treatment | Full coverage of wall voids and crawlspaces | Persistent or widespread infestations |
DIY Traps and Baits
A simple jar trap works well: wrap the outside of a glass jar with tape so the insects can climb in, bait it with a piece of starchy food or damp paper, and leave it overnight. Commercial traps with a slow-release attractant catch more over a longer period, and they double as a monitoring tool, because a trap that keeps filling tells you the source is still active.
Using Insecticides Safely
Dust products such as diatomaceous earth and boric acid outlast sprays because they stay where you put them. Apply dusts in a thin layer; a visible pile actually deters insects, which avoid walking through it. Keep dust out of reach of children and pets, never apply sprays directly to food storage areas, and follow the label’s re-entry times.
Clearing stacked paper and cardboard is the most understated step, because those piles are silverfish food and a documented fuel source in house fires, so removing them reduces two risks at once.
Prevention: Seal, Dry, and Declutter
Prevention is the mirror image of removal: make the house less humid, less drafty, and less appetizing.
A Seven-Step Prevention Checklist
- Fix plumbing leaks promptly. A slow drip under a sink keeps a microclimate of humidity that silverfish and mold both love.
- Ventilate bathrooms and laundry rooms. Run the exhaust fan during showers and for 15 minutes after, and leave closet doors open where possible.
- Store paper goods in sealed plastic bins instead of cardboard boxes. Cardboard is food and shelter in one package.
- Inspect incoming boxes and grocery bags before they come inside, since silverfish hitchhike in deliveries.
- Vacuum baseboards, the backs of appliances, and closet floors weekly during an active problem.
- Keep firewood, lumber, and stored paper away from the foundation line.
- Maintain gutters and downspouts so water drains away from the house instead of seeping into the crawlspace.
Moisture control is the core of prevention, and airtight building strategies such as passive house construction show how far design can go: vapor barriers, continuous insulation, and controlled ventilation keep interior humidity stable enough that moisture-loving pests struggle to establish themselves.
A Routine That Keeps Silverfish Out for Good
Homes that stay silverfish-free do not run a one-time campaign; they keep a small, repeating routine.
Seasonal Checks
- Monthly: wipe shelves, vacuum corners, and check under sinks for damp spots. Look inside storage boxes for the pepper-like specks.
- Quarterly: inspect the crawlspace or basement for condensation, replace any damp cardboard, and clean behind the washing machine and dryer.
- Yearly: re-caulk window frames and baseboard gaps, replace weatherstripping, and check the attic for leaks before winter.
Call a licensed pest control company when traps keep refilling, when damage appears in multiple rooms, or when the entry point stays hidden. A typical treatment runs $150 to $400 depending on house size and the severity of the infestation, and a few silverfish sighted over a month usually means a small, localized population that traps and sealing can handle on their own.
For houses with chronic moisture problems, the lasting fix is structural: many home remodeling projects now fold moisture control into the plan from the start, addressing drainage, ventilation, and insulation while the walls are open, which removes the conditions silverfish depend on before they ever get a foothold.