Silverfish eat starchy materials in your home, including paper, book bindings, wallpaper paste, clothing, and stored food packaging. They don’t bite, don’t carry diseases, and pose no direct threat to people or pets. But over time, a silverfish population can cause real damage to books, documents, photos, fabrics, and anything containing cellulose or adhesive.
What Silverfish Eat
Silverfish feed on carbohydrates and cellulose. In practical terms, that means almost anything made from paper, glue, starch, cotton, linen, or certain synthetic fibers is fair game. They’re drawn to the glue in book bindings, the starch in paper, and the paste behind wallpaper. They have a particular preference for glazed paper with a starchy coating or a glossy finish, so magazines and photo albums are common targets.
Their diet extends well beyond your bookshelf. Silverfish eat starched linens, curtains, upholstery, and anything made of silk or cotton. They’ll chew through cardboard boxes in storage, contaminate dry food in pantries, and work through wallpaper from the back side where the adhesive sits. Because they’re nocturnal and prefer hidden spaces, most people don’t notice the damage until it’s accumulated over weeks or months.
What the Damage Looks Like
Silverfish leave behind irregular holes, chewed edges, and rough patches on paper, cardboard, and fabric. The feeding marks don’t follow clean lines the way a tear would. Instead, you’ll see surface scraping or small, uneven notches along page edges and document corners. On wallpaper, the damage often appears as peeling or bubbling where the adhesive has been eaten away from behind.
Beyond chewing damage, silverfish leave droppings that look like tiny black pepper-like specks, and these can stain surfaces. They also shed scales throughout their lives, leaving behind small, translucent skin casings in the areas where they’re most active. Finding clusters of shed skins, small stains on paper or fabric, or irregular feeding marks in dark, humid corners of your home are the classic signs of an infestation.
Are Silverfish Harmful to People or Pets?
Silverfish have very weak jaws, not nearly strong enough to pierce human skin. They aren’t known to carry pathogens or transmit any diseases. If your cat or dog eats one, that’s not a toxicity concern either.
The one health consideration is allergies. Silverfish shed their scales continuously, and those shed skins collect dust and contain proteins similar to those found in dust mites. For people already sensitive to indoor allergens, this can trigger symptoms like a runny nose, itchy eyes, or breathing problems. A 2008 lab study found that silverfish may worsen allergic respiratory symptoms in people sensitive to common indoor allergens, though the evidence is limited.
Where They Live and Why
Silverfish need high humidity to survive. They prefer relative humidity between 75% and 95%, and they can’t survive long in environments below 50%. This is why they show up most often in bathrooms, laundry rooms, kitchens, basements, and poorly ventilated attics. They also favor warm environments, since heat speeds up their metabolism and reproduction. Spots near heating ducts, hot water pipes, and appliances that generate warmth are prime territory.
They’re strictly nocturnal. During the day, silverfish hide in cracks, behind baseboards, inside boxes, between books, and under appliances. They avoid light and move quickly when exposed, which is why most people only spot them during a late-night trip to the bathroom or when pulling out a box from storage.
How Long They Live and Reproduce
Silverfish are surprisingly long-lived for insects. In ideal conditions of high humidity and warmth, they can live about three years. Females produce one to three eggs per day, sometimes laying clusters of up to twenty at once. That steady egg output means a small population can grow quickly in a favorable environment.
Unlike most insects, silverfish continue to molt throughout their entire lives rather than just during development. Some species undergo more than 50 molts over a lifetime. Each molt leaves behind a tiny skin casing, which is part of why their shed scales accumulate in infested areas.
Silverfish vs. Firebrats
If the bug you found looks like a silverfish but has a mottled brown or gray color instead of a pearly silver, it’s likely a firebrat. The two are close relatives with similar body shapes and behavior, but firebrats prefer much warmer, drier conditions. Firebrats thrive at temperatures above 90°F (optimally around 98° to 102°F) and can tolerate humidity as low as 30%. You’ll find them near ovens, furnaces, fireplaces, and hot water pipes rather than in damp basements. Silverfish, by contrast, are silver or pearly gray and need that 75%+ humidity to stay alive.
How to Get Rid of Them
The most effective long-term strategy is reducing humidity. Since silverfish can’t survive below 50% relative humidity, running a dehumidifier in problem areas like basements, bathrooms, and laundry rooms directly undermines their ability to live in your home. Fix leaky pipes, improve ventilation in crawl spaces, and use exhaust fans in bathrooms during and after showers.
For direct control, food-grade diatomaceous earth works by physically damaging the waxy outer coating on silverfish, causing them to dehydrate. Dust it thinly along baseboards, behind furniture, and in hidden crevices where silverfish travel. It needs to stay dry to work, so reapply after cleaning or if the area gets damp. Boric acid applied as a thin dust in cracks and concealed spaces is another option that targets silverfish along with other pests that favor the same humid environments.
Reducing their food supply also helps. Store important papers, photos, and books in sealed plastic bins rather than cardboard boxes. Keep dry pantry goods in airtight containers. Move storage boxes off basement floors and away from walls where moisture collects. These steps won’t eliminate an established population on their own, but combined with humidity control, they make your home far less hospitable to silverfish over time.