How to Get Rid of Silverfish in the Bathroom for Good

You flip on the bathroom light at 2 a.m. and something silver darts across the tile and vanishes behind the toilet. That was a silverfish — and if you’ve seen one, there are almost certainly more. Learning how to get rid of silverfish in the bathroom for good isn’t about one magic spray. It’s about understanding why your bathroom is paradise for them, then systematically taking that paradise away.

The good news: silverfish don’t bite, don’t spread disease, and don’t damage your home’s structure. The bad news: they’re nocturnal, fast, excellent at hiding, and can live for months without eating. Killing the ones you see changes nothing. You have to make the bathroom uninhabitable for them — and then keep it that way.

Why Silverfish Love Your Bathroom

Silverfish (Lepisma saccharina) are ancient insects — they’ve been around for roughly 400 million years, which tells you something about how hard they are to discourage. They thrive in exactly the conditions most bathrooms provide:

• High humidity. Silverfish need relative humidity above 75 percent to really flourish. A bathroom after a hot shower easily hits 90 percent.
• Warmth. They prefer 70 to 80°F — normal indoor temperatures.
• Dark hiding places. Behind toilets, under sinks, inside wall voids around pipes, behind loose tiles, in the gap between the tub and the wall.
• Food. They eat starches and carbohydrates: paper, book bindings, wallpaper paste, glue, dead skin cells, hair, cotton, linen, even the sizing in some fabrics. A bathroom with a stack of magazines, cardboard boxes of toiletries, or wallpaper is a buffet.

They’re nocturnal, so daytime sightings usually mean the population is large enough that some are being crowded out of hiding spots — or that conditions are so good they’re active around the clock. Either way, it’s time to act.

Step 1: Dry It Out (The Single Most Important Step)

Everything else on this list helps, but nothing matters as much as moisture control. Drop the humidity and you make the bathroom fundamentally hostile to silverfish. They dehydrate, their eggs fail to hatch, and the population collapses.

Run the exhaust fan — properly. Turn it on before your shower and leave it running for 20 to 30 minutes after. If your fan is weak, loud, or more than 10 years old, consider replacing it — a modern quiet fan (look for 1.0 sones or less) is far more likely to actually get used. The fan should vent to the outside, not into the attic.

Fix every leak, no matter how small. A dripping faucet, a sweating toilet tank, a slow seep under the sink — each one creates a permanent damp microclimate. Check under sinks with a flashlight, feel around toilet bases for moisture, and look for water stains on ceilings below upstairs bathrooms.

Squeegee the shower. A 30-second squeegee after showering removes most of the water that would otherwise evaporate into the room. It also prevents mold, so it’s a double win.

Consider a small dehumidifier if the bathroom has no window and no effective fan. Even a compact desiccant unit can pull a surprising amount of moisture from a small bathroom. Aim to keep relative humidity below 50 percent — uncomfortable for silverfish, perfectly comfortable for you. (A $15 humidity gauge tells you exactly where you stand.)

Don’t leave wet towels and bathmats bunched up. Hang them spread out so they dry fully between uses. A damp bathmat left in a heap is practically a silverfish nursery.

Step 2: Remove Their Food and Hiding Places

Silverfish eat things you’d never think of as food. Walk through your bathroom with fresh eyes:

• Get rid of cardboard. Boxes of toiletries, stored toilet paper in cardboard packaging, that stack of old magazines — move them out or transfer contents to sealed plastic bins.
• Declutter under the sink and behind the toilet. Every undisturbed pile is shelter. If you haven’t touched it in six months, it goes.
• Store linens properly. Don’t leave piles of towels or clothes on the bathroom floor. Use closed hampers and cabinets.
• Check wallpaper. If your bathroom has wallpaper, especially older paper with paste adhesive, inspect the edges. Peeling, bubbling wallpaper is both a food source and a hiding place. In a chronic silverfish bathroom, removing wallpaper in favor of paint or tile is a legitimate long-term fix.

Step 3: Seal Their Highways

Silverfish are flat and flexible — they slip through cracks you’d swear were sealed. A tube of caulk and an afternoon closes most routes:

• Caulk around the tub, shower, and toilet base where they meet the floor and walls. If existing caulk is cracked, moldy, or peeling, scrape it out and redo it.
• Seal around pipes where they enter walls — under sinks, behind toilets. Use caulk for small gaps; expanding foam for larger ones.
• Repair grout. Cracked or missing grout between tiles creates perfect silverfish harborage. Regrout damaged areas.
• Check baseboards. Gaps between baseboards and the floor or wall are classic entry points. Caulk them.
• Don’t forget the medicine cabinet and vanity. Gaps behind these fixtures are prime hiding spots — seal what you can reach.

This won’t make your bathroom airtight (and it shouldn’t be — you need ventilation), but it eliminates the easy indoor routes and forces silverfish into the open where traps and treatments can reach them.

Step 4: Trap the Ones Already Inside

With moisture dropping and hiding places shrinking, traps clean up the existing population:

The jar trap (free and surprisingly effective): Wrap the outside of a small glass jar with masking tape (for grip), and put a piece of bread or a dab of honey inside. Set it upright where you’ve seen silverfish. They climb the textured tape, drop in for the food, and can’t climb the smooth glass to escape. Check each morning and empty into soapy water.

Sticky traps: Place flat glue-board traps (the kind sold for roaches) along baseboards, behind the toilet, and under the sink. These won’t end an infestation alone, but they’re excellent monitors — the number you catch tells you whether your other measures are working.

Newspaper trap: Roll up a damp newspaper, secure it with a rubber band, and leave it overnight in the bathroom. Silverfish love the damp paper. In the morning, shake it out into a sealed bag outdoors — don’t unroll it inside.

Run traps for two to three weeks. Declining catches mean you’re winning.

Step 5: Targeted Treatments for Stubborn Infestations

If moisture control, sealing, and trapping haven’t solved it after a month, add one of these:

Diatomaceous earth (food grade): This fine powder is made from fossilized algae. It’s generally regarded as low-toxicity for mammals, but it can irritate eyes and lungs — never treat it as completely harmless. It kills insects mechanically — the microscopic sharp edges damage their waxy outer coating and they dehydrate. Puff a thin layer into cracks, behind the toilet, under the sink, and along baseboards using a bulb duster. Key rules: it only works when dry (useless in a wet bathroom — which is why you did Step 1 first), wear a dust mask when applying, and use food-grade, not pool-grade.

Boric acid powder: Similar application to diatomaceous earth, but it’s a stomach poison as well as a desiccant — silverfish that groom the powder off themselves ingest it. Apply thinly in voids and cracks where pets and children can’t reach. Don’t over-apply; a barely-visible film is more effective than piles (insects avoid heavy deposits).

What not to use: Skip the total-release foggers. They coat surfaces you touch daily, don’t penetrate the cracks where silverfish actually live, and the moisture from your bathroom degrades most residual sprays quickly anyway. Targeted powders in dry voids outperform broadcast spraying for silverfish every time.

What Doesn’t Work (Save Your Money)

• Ultrasonic repellers. No credible evidence they affect silverfish. The plug-in devices with the blue light are modern snake oil.
• Essential oil sprays. Cedar, lavender, and citrus sprays may repel silverfish briefly, but the effect fades in hours and does nothing about the population or the moisture problem.
• Mothballs. They contain naphthalene or paradichlorobenzene — both hazardous in enclosed spaces, both illegal for unlisted uses in many places, and largely ineffective against silverfish anyway.
• Just spraying the ones you see. Contact killer on a visible silverfish feels productive. It isn’t. You’re treating 1 percent of the problem.

Preventing Their Return

Silverfish control is really humidity control with pest control as a side effect. The long-term habits that keep them away:

• Keep the exhaust fan habit permanent — 20 to 30 minutes after every shower, forever.
• Re-caulk the tub and sink areas every few years before gaps open up.
• Keep bathroom humidity below 50 percent year-round (winter heating usually helps; summer humidity is the danger season).
• Store nothing on the bathroom floor long-term.
• Fix leaks the week they appear, not the month after.
• If you renovate, choose tile and paint over wallpaper, and ask for mold-resistant drywall in wet areas.

Do these and your bathroom becomes one of the least hospitable rooms in the house for silverfish — which is exactly the goal.

When to Call a Professional

Silverfish are a DIY-friendly pest, but call a pro when:

• You’ve controlled moisture, sealed, and trapped for six weeks with no real improvement (there may be a hidden moisture source — a slow pipe leak inside a wall, for example — that needs professional detection)
• Silverfish are appearing in large numbers throughout the house, not just the bathroom (suggests a bigger moisture or entry-point problem)
• You find them in stored valuable items — books, documents, photographs, stamp collections — where you want expert treatment that won’t damage the items
• There’s visible water damage, mold, or soft drywall accompanying the infestation (that’s a moisture-remediation job first, pest job second)

A professional visit for silverfish typically runs $100 to $200 and should include a moisture assessment, not just spraying.

Frequently Asked Questions

Are silverfish dangerous? Do they bite?
No. Silverfish don’t bite humans or pets, don’t spread disease, and aren’t venomous. They’re a nuisance pest — the damage they do is to paper goods, books, wallpaper, and fabrics, not to people.

Why do I only see silverfish at night?
They’re nocturnal and strongly avoid light. If you’re seeing them during the day, the population is likely large or their hiding spots are disturbed — both signs to take the problem seriously.

How long do silverfish live?
Remarkably long for their size — two to three years, sometimes more. Females lay eggs continuously in small batches, which is why infestations build slowly and persist. The upside: they’re slow breeders compared to roaches, so consistent control measures genuinely work.

Can silverfish come up through drains?
They can travel through drain pipes, yes — drains connect to the same moist, dark pipe chases they love. A drain cover helps, but the real fix is reducing the moisture and food that make your bathroom attractive once they arrive.

Will silverfish go away on their own in winter?
They may become less active in cold, dry winter air — but they don’t leave. They retreat deeper into wall voids and wait. If you only treat in summer when you see them, you’ll fight the same battle every year. Winter is actually the best time to seal entry points while they’re inactive.

I found silverfish in my bedroom too. Is it the same problem?
Probably related. Bedrooms adjacent to bathrooms share wall voids and plumbing chases. Treat the moisture source (the bathroom) and the satellite rooms usually clear up. If they’re in dry rooms far from moisture, look for other humidity sources — a damp basement below, for instance.

The Bottom Line

Getting rid of silverfish in the bathroom for good comes down to one principle: they’re there for the moisture, and everything else is secondary. Dry the room out with real ventilation and leak repair, remove their food and hiding spots, seal the cracks, trap the stragglers — and do it in that order. Most bathroom silverfish problems resolve within a month of serious moisture control, no exterminator required.

Start tonight: run that exhaust fan for 30 minutes after your shower, and you’ve already taken the most important step.

📚 Sources & Further Reading

• NPIC: Diatomaceous Earth General Fact Sheet
  Inhalation, eye, and skin irritation risks of diatomaceous earth and recommended protective steps.
• NPIC: Boric Acid General Fact Sheet
  Safety profile of boric acid powder for crack-and-crevice use.

🚨 If someone ingests a pesticide or shows poisoning symptoms, call Poison Control immediately: 1-800-222-1222 (U.S.).

Related Guides

• How to Get Rid of Cockroaches in the Kitchen Permanently (Step-by-Step) – another moisture-loving pest and how to beat it
• How to Unclog a Drain Without a Plumber (5 Methods That Work) – fixing the damp conditions pests love
• “Spring Pest Prevention Checklist: Keep Bugs Out All Year” – keep bathrooms pest-free all year