Does a dehumidifier get rid of silverfish?

Yes, and not in the way most people mean it. A dehumidifier is habitat control, not extermination. Silverfish are one of the few household pests whose presence is genuinely governed by humidity, so drying the air is one of the few genuinely effective things you can do about them. It will not kill the ones already behind your bathroom skirting. It removes the conditions that let a population feed, breed and persist, and the population then declines on its own schedule — over weeks and months, not overnight.

That is a worse sales pitch than “kills silverfish fast” and it is what actually happens. If you want them gone this weekend, a machine is the wrong purchase and this page says so further down.

Silverfish are usually described as thriving above roughly 75% relative humidity, and as struggling to reproduce once the air around them stays below about 50%. Eggs are the weak link — they need damp air to develop, and dry air is a far bigger problem for an egg than for an adult. Those two figures are the whole mechanism. Everything else on this page is about hitting the second one in the places where the insects actually are.

Conveniently, that ceiling is the same one this site recommends for other reasons. 50% RH is the top of the comfortable band; above 60% you are in the range where mould and mildew grow on damp material. Below about 30% the air is drier than most people want to live in. Aiming at 45% gives you room to drift on a humid week without crossing back over.

This is the part almost nothing written about silverfish covers, and it is the reason people buy a dehumidifier, watch the display settle at a respectable number, and still find silverfish in the bathroom cabinet.

Relative humidity is relative to temperature. The same air, unchanged in moisture content, reads a higher RH when it is colder. The fixed quantity is the dew point — the temperature at which that air would be saturated. A room at 72°F and 55% RH has a dew point of 55°F. Every surface in that room colder than 55°F is wet. Every surface a few degrees above it is sitting in a film of air far damper than the room reading suggests.

Under-sink cabinets, the backs of built-in wardrobes on an exterior wall, the underside of a basement stair, the boxes stacked against a foundation wall — these are all colder than the room and barely ventilated. The hallway hygrometer describes the hallway. It has never been inside the cupboard.

Read the 78% cell. A room most people would call fine — 55% RH, 72°F — puts a 62°F cupboard panel in silverfish territory. Pull the room down to 45% and that same panel drops to 64%. Nothing about the cupboard changed. Nobody insulated it, nobody drilled a vent. Ten points off the room reading moved the micro-environment across the threshold, and that is the entire case for a dehumidifier here.

It also explains a common false negative: a room that reads 45% can still have a problem spot if some surface in it runs much colder than 58°F — a poorly-insulated corner, an uninsulated cold-water pipe, a slab floor in spring. Measure in the place you are finding them, not in the doorway.

Silverfish want three things in one place: damp, dark, and starch. Bathrooms and laundries supply the first two and get the third from paper and from the sizing in wallpaper paste. Basements supply all three by default. Kitchens supply them under the sink, where the cabinet is closed, the plumbing is cold, and the base is often the coldest floor in the house.

Cardboard is the one worth singling out. A cardboard box in a damp basement is not storage that happens to be near a pest problem — it is food, shelter, egg site and humidity buffer in a single object. Corrugated board is cellulose, it wicks and holds moisture, the flutes are exactly the dark crevice the insect looks for, and the glue is starch. So is the paper inside it. The same is true of stacked newspaper, old books stored flat, and paper-faced plasterboard offcuts left leaning against a wall.

This matters for the dehumidifier argument specifically, because cardboard holds moisture long after the air around it has dried. You can run a machine for a week, hit your target on the display, and have a stack of damp boxes still sitting at their own humidity in the corner. Dry air pulls it out of them eventually. Removing them does it immediately, and costs nothing.

Three separate clocks, and people usually only count the first one.

The air: hours to a day or two. A correctly sized unit in a closed room hits its setpoint fast, and this is the only stage the display shows you.

The materials: days to a few weeks. Timber, plaster, stored paper, cardboard and fabric all release moisture slowly, and while they do the room keeps climbing back after the machine cycles off. A basement that reads target on day two and drifts up overnight is not a broken machine; it is the contents equalising. Judge the room on where it sits after a fortnight of continuous running, not on day one.

The insects: a season. This is the part to be honest about. You are not killing anything. You are removing the conditions that let eggs develop and juveniles survive, and then waiting out the adults already present — and silverfish are commonly reported to live for several years, unusually long for an insect that size. Sightings should thin out over months. Anyone promising a fortnight is selling something.

Four cases where buying one is the wrong move, and we would rather say so than sell you a machine that cannot work:

The room already reads below 50%. If you have measured — in the problem spot, not the hallway — and it is genuinely dry there, humidity is not what is sustaining them. Drying it further will not help. Look for a damp void next door, or accept that this is a pest-control problem.

There is an active leak. A dripping trap, a failed shower seal, a weeping supply line or water tracking in through a foundation crack will out-supply any machine you can buy. A dehumidifier run against a live leak is a device you are paying to evaporate water you are also paying for, and the leak is still rotting whatever it is soaking. Find it first. This is a plumber, not a purchase.

You need them gone now. A large established population in a house you are selling next month is not a habitat-control timeline. That is a pest-control problem, and a professional can treat the harbourage directly. Drying the space still helps afterwards — it is what stops the population re-establishing — but it is the second step in that order, not the first.

The damp room is a crawl space or an unsealed cellar with a soil floor. Ground moisture evaporating off bare earth is a continuous supply, and the standard fix starts with a vapour barrier over the soil. A dehumidifier down there without one is working against the ground.

One thing to know before you compare any two machines, because it is the single most common sizing error in this category. In 2019 the US Department of Energy changed the dehumidifier test condition from 80°F to 65°F. Machines remove less moisture from colder air, so the same hardware now earns a lower number. A modern “50 pint” unit removes roughly what a pre-2019 “70 pint” did. Every sizing chart written before 2019 — and most of the ones circulating now, because they were copied from those — is on the old scale. Follow one with a current machine and you undersize by about a third. We publish both numbers and label which is which.

Second thing: ignore the square-footage claim on the box. In our own product data, three units all rated 155 pints/day advertise coverage of 7,500, 6,000 and 6,000 sq ft, and a 160-pint unit advertises 2,500. There is no standard behind that figure. Size on pints per day, which is tested.

A dehumidifier does one job. These cost little or nothing and remove the parts of the problem it cannot reach:

Get the cardboard out. Sealed plastic totes are not a marginal improvement on boxes — they are a different category of storage, with no food value, no crevices and no moisture buffer. This is usually the highest-value change on the list.

Fix the leak, then run the machine. In that order, always.

Use the bathroom fan properly. During the shower and for fifteen to twenty minutes after, which is when the moisture is still coming off wet surfaces. A fan switched off with the light does roughly half the job it could.

Get stored paper off the floor and away from exterior walls. Both are colder than the room, which is exactly the point the table above makes.

Buy a cheap hygrometer and put it in the problem spot. Inside the cabinet, on the basement floor, behind the wardrobe. A ten-dollar sensor in the right place tells you more than an expensive one in the hall, and it is the only way to know whether the machine is doing anything where it matters.

Run it continuously, drained, not on a timer. Habitat control is about the humidity the insects experience for weeks, not the average over a day. A tank that fills and stops the machine at 3am is a gap in the treatment.

We have never run these units, in a basement or anywhere else, and we have never counted an insect. There are no field tests behind this page and no reviewer with a clipboard. What we do instead is publish the arithmetic — the dew points, both rating scales, the sizing baseline and where it comes from — so you can check every number on this page against a psychrometric chart and the DOE rule yourself.

The humidity thresholds for silverfish are published entomology, quoted here as approximate because that is how they are published. We are not a health authority and make no claims about what any of this means for anybody’s health; if that is your question, ask someone qualified to answer it. For an established infestation, a licensed pest-control operator will do more in an afternoon than this page can, and they earn us nothing.

Product data and prices are a snapshot taken 21 August 2026 and will drift. Capacities are manufacturer figures on the modern DOE scale.