No. Silverfish have weak, scraping mouthparts built for grazing on paper and starch. They cannot pierce human skin, don't sting and don't feed on blood. A 'silverfish bite' is almost always something else, such as a flea, bed bug or mosquito bite.

Are silverfish harmful or dangerous?

Not to people or pets. They carry no known disease. The harm is to belongings: books, documents, photos, wallpaper, cardboard boxes and starched fabrics, and Iowa State notes even that is significant only with very large, long-standing infestations. Their scales and droppings can add a little to indoor allergens.

What do baby silverfish look like?

Newly hatched nymphs are about 1/16 inch, plump, white and scaleless, with the same tapered body and three tail bristles. They pick up silver scales after their fourth molt, per UC IPM.

What do silverfish eggs look like?

Tiny (1/32 to 1/25 inch), oval, whitish eggs that turn yellowish, laid in cracks, behind baseboards, on cloth or in stored paper. Clutches average about 50. You will almost never find them before you find the insects.

What bugs look like silverfish?

Firebrats (same shape, mottled brown, in hot spots), gray silverfish (larger, very long tails), jumping bristletails (outdoors, hump-backed, jump), earwigs (pincers), house centipedes (15 pairs of long legs) and young cockroaches (wider, no long tail bristles).

Why did I find a silverfish in my bed?

It was wandering at night looking for food or moisture. Silverfish don't live in beds or feed on people; a damp bedroom (a humidifier, a rainy week, an exterior wall) or a nearby bathroom makes stray visits more likely.

Is one silverfish a sign of an infestation?

Not by itself. Utah State Extension notes they're present in most buildings. Several a night, nymphs, or grazed paper mean a breeding population; see why silverfish are in your house.

Silverfish: What They Are, What They Eat, Are They Harmful?

Q: What do silverfish eat?

Starches, sugars and proteins: paper and book bindings, wallpaper paste, cardboard, photographs, cotton, linen, rayon and silk (especially starched), cereals and flour, cornstarch-based cosmetics, mold, dandruff and dead insects. They can go close to a year without food if they have water.

Silverfish are small, wingless, silvery insects that live in damp parts of a house and feed on paper, glue, starch and other carbohydrates. They don't bite, sting or spread disease, so they are harmless to people; the damage they do is to books, documents, wallpaper and stored clothing.

They're among the oldest insects on Earth, little changed for hundreds of millions of years, and Utah State Extension notes they're present in most buildings. What decides whether you see one a month or ten a night is mostly moisture, cardboard and time. This page covers how to identify them, the species you might have, what they eat and do, and what that means for you.

What is a silverfish?

The common silverfish (Lepisma saccharina) is a primitive insect in the order Zygentoma. It has never had wings, and the young look like small adults instead of going through a larva stage.

How to recognize one:

Body: about 1/2 inch, up to 3/4 inch (gray silverfish can reach about 1 inch), flattened and carrot-shaped: wide at the head, tapering to the tail.
Color: silvery to pearl gray, covered in fine scales with a metallic sheen. The scales rub off like powder and stick to surfaces, and UC IPM points out that finding these scales around damaged paper is a good clue.
Ends: two long antennae at the front, three long bristles at the back. The tail bristles are the giveaway.
Movement: fast, wiggly, fish-like runs, mostly at night. The classic sighting is something darting under the bath mat when you switch on the light, or one stuck in the tub.

Silverfish species in US homes

Species	Look	Where and when
Common silverfish (Lepisma saccharina)	Silver, about 1/2 inch	Bathrooms, basements, closets; needs high humidity (above 75% at warmer temperatures, per UC IPM)
Gray or long-tailed silverfish (Ctenolepisma longicaudata)	Grayer, larger (up to about 1 inch with very long tails and antennae)	Anywhere indoors, including dry rooms and new homes; thrives at about 55 to 60% humidity, according to the UK pest trade body BPCA
Four-lined silverfish (Ctenolepisma lineata)	Faint dark stripes	Outdoors in mulch, moving into attics and wall voids, more in warm states
Firebrat (Thermobia domestica)	Mottled gray and brown, bristly	Hot spots above 90 °F: furnaces, water heaters, dryers, boiler rooms, summer attics; tolerates humidity as low as 30%

The gray silverfish matters because it breaks the "silverfish mean damp" rule. If you see them in a dry, modern apartment or a house built in the last few years, it is likely this species, and it usually arrives in cardboard boxes.

Firebrat, a mottled gray-brown bristletail, on a warm heating pipe

Baby silverfish and eggs

UC IPM gives the details. Eggs are about 1/25 inch, oval and whitish, laid in crevices, on cloth or in dust and stored paper, in clutches that average about 50. Silverfish eggs hatch in 19 to 32 days (firebrats in about 2 weeks). Newly hatched nymphs are about 1/16 inch, plump, white and scaleless; people describe them as "tiny white bugs with tails." They get their silver scales after the fourth molt.

Growth depends heavily on temperature: above 75 °F a silverfish can reach adulthood in about 60 days, while below 50 °F it can take up to 500 days. Unusually for insects, they keep molting all their lives, 45 to 60 times, and Virginia Tech notes they must mate again after each molt. Females lay fewer than 100 eggs in a lifespan of 2 to 8 years.

That slow pace is why a large silverfish population takes a long time to build. If you're seeing many, the conditions have suited them for a while, and it also means they won't disappear in a week.

What do silverfish eat?

Silverfish have gut enzymes that digest cellulose, which most insects can't. Their menu, from UC IPM, UF/IFAS and Virginia Tech:

paper with glue or sizing, book bindings, magazines, cardboard boxes;
wallpaper and wallpaper paste;
photographs (the gelatin coating);
cotton, linen, rayon and silk, especially starched or stored unwashed;
flour, cereal, pasta, oats and pet food in open packages;
cornstarch-based cosmetics and powders in bathrooms;
mold, household dust, dandruff, glue and dead insects.

They can survive close to a year without food if water is available, but not long in dry air. Moisture limits most species far more than food does.

What do silverfish do, and are they bad?

They're bad for paper, not for people. Their jaws are too weak to bite, so they scrape: UC IPM describes feeding that starts in one spot and spreads as unconnected, irregular holes, with gray grazed patches, missing letters, yellow or brown stains from associated fungi, and tiny pepper-like droppings.

Ragged, grazed edge of an old book page and wallpaper damaged by silverfish — Irregular grazed edges, small holes and yellowish stains point to silverfish. Moth damage comes with larvae and silk.

How bad it gets depends on numbers and time. Iowa State Extension notes that damage is significant only with very large infestations present over long periods. A few silverfish in a bathroom won't ruin your books; years of them in boxes in a damp basement can.

Do silverfish bite? Are they dangerous?

No. There's no such thing as a silverfish bite on a human. They don't carry pathogens and don't sting. The only health angle is allergens: like dust mites and cockroaches, their shed scales and droppings can add to indoor allergens for sensitive people, though this is minor. If you have unexplained bites, look at bed bugs, fleas or mosquitoes instead.

What silverfish do signal is a moisture problem in the house: a leaky shower pan, a poorly ventilated bathroom, a damp basement, attic condensation. Those matter more for the house than the insects do. A silverfish population also feeds the house centipedes that hunt them.

Bugs that look like silverfish

Bug	How to tell it apart
Firebrat	Same shape, but mottled brown/gray; found in hot spots
Gray silverfish	Larger, duller gray, tail bristles and antennae longer than the body
Jumping bristletail	Hump-backed, can jump; outdoors in leaf litter, rarely inside
Earwig	Brown, with pincers instead of three bristles
House centipede	15 pairs of long legs; it's a predator of silverfish
Springtail	Tiny (under 1/8 inch), jumps, no scales
Young cockroach	Wider and oval, two short cerci, no long tail bristles
Pill bug	Gray, armored, rolls into a ball, slow

People also call silverfish "paperfish" or "fishmoths"; those are the same insects. In the other direction, plenty of "silverfish" questions online turn out to be house centipedes, so count the legs: silverfish have six.

Where they hide, and why they're in your house

Common silverfish prefer around 71 to 90 °F with high humidity. Indoors that means bathrooms, under sinks, basements, laundry rooms, crawl spaces, attics with condensation, and closets on an outside wall. During the day they crowd together in a sheltered spot, behind baseboards, under loose tile, in wall voids, book stacks and cardboard boxes, and the females lay eggs there.

They usually arrive in cardboard boxes and stored items, or crawl in from mulch and leaf litter. UC IPM notes that new homes can be invaded from surrounding wild areas as those dry out in summer, and that fresh concrete and green lumber supply the moisture. In apartments, UF/IFAS notes they follow pipelines from unit to unit. Full details are in why silverfish are in your house.

What people who dealt with them say

Silverfish threads on r/pestcontrol and similar forums follow a pattern:

The reaction is mostly disgust and anxiety, not damage. The most upvoted threads are about finding one in a bed or a drawer. Pros and other posters keep repeating the same reassurance: they can't hurt you, and one in the bed was wandering, not nesting.
Humidity is the first fix people report working. In one widely shared thread, the person seeing them nightly had been running a humidifier for houseplants during a rainy week; the top advice was simply a dehumidifier.
Natural repellents get tried first and rarely settle it. Lavender oil, cedar rings and bay leaves come up constantly; a few people credit them, almost always alongside lowering humidity.
"No damp, still silverfish" usually comes from new builds and modern apartments, and the knowledgeable replies point to gray silverfish, which tolerate drier air and travel in cardboard. Getting rid of old boxes and using bait packs is the typical advice there.
Apartments are the hardest case. A pest tech moderating r/exterminators notes they're difficult to eliminate completely when you can't treat connected units, attics and crawl spaces.

How to get rid of silverfish (short version)

Dry the house. A dehumidifier to keep relative humidity under 50 percent, the bathroom fan for 20 to 30 minutes after showers, and leak repairs. (This helps against silverfish, but not firebrats, which like hot, dry spots.)
Take away the cardboard. Move paper, books and clothing into tightly sealed plastic bins; silverfish don't chew through plastic.
Seal hiding spots. Caulk gaps at baseboards, tub edges, cracked grout and pipe penetrations.
Trap and treat. Sticky traps to monitor, a light dusting of diatomaceous earth or boric acid in dry voids, and a labeled crack-and-crevice insecticide if numbers stay high.

The step-by-step plan, including what fails and how long it takes, is in how to get rid of silverfish.

When to call a pro

A few silverfish in a bathroom are not an emergency, and Iowa State notes control may not be needed at all if only a few are present and nothing is damaged. Consider a professional if you're seeing them in many rooms despite a dehumidifier, if valuable papers, archives or collections are at risk, or if you suspect a hidden leak inside a wall. A good company will look for the moisture source as well as treat. If they only offer to spray baseboards every month and never mention humidity or cardboard, you're paying to manage a symptom.

Silverfish