What to Know About Silverfish

Medically Reviewed by Carol DerSarkissian, MD on July 13, 2023
4 min read

Silverfish are pests commonly found around the world. They are harmless insects, but they can infest your home.

Silverfish are shiny silver insects with scales and antennae. They don’t have wings, but they have a soft body and are covered in fine scales that look like a fish.

They have a flat and oval-shaped body. Adults are usually about ¾ inch long with two antennae and 3 tail projections. A firebrat is a similar insect, but it is usually darker and mottled grey.

Silverfish like the dark. They hide during the day and avoid direct sunlight. If you move an object they are hiding in or under, they will dart out and find another dark hiding place.

Female silverfish lay eggs constantly after reaching the adult stage. They lay eggs in crevices and cracks around your home, which hatch within 3 weeks. Young insects reach the adult stage within 4 to 6 weeks.

Young silverfish look like adult silverfish, only smaller and white. These insects live a long life, anywhere from 2 to 8 years. They can also survive a long time without food, sometimes up to a year. However, they are sensitive to moisture and need high humidity to survive.

Silverfish grow in damp, dark, and cool places. Large populations can grow in new buildings with wet brick and stone. You might also commonly find them in:

  • Basements
  • Sinks
  • Bathtubs
  • Closet shelves
  • Behind baseboards
  • Bookcases
  • Behind windows
  • Behind door frames

Silverfish and firebrats are chewing insects and general feeders. They eat carbohydrates and protein, including:

  • Flour
  • Rolled oats
  • Dried meat
  • Paper
  • Cardboard
  • Books
  • Glue
  • Vegetables
  • Cereals
  • Dead insects

Sometimes they can enter into a new home in cardboard cartons, boxes, papers, and books that come from infested places.

These insects are generally nuisance pests. They won’t hurt you, but they can contaminate your food. Silverfish leave their poop behind in your food, so make sure to check for any insects. Discard anything that has bugs in it.

While silverfish won’t make you sick or bite you, they can destroy your home. Because they are chewing insects, they can eat through your belongings. Their poop will also cause stains.

Glue. Silverfish eat glue. They can eat the glue in wallpaper, book bindings, carpet, curtains, and furniture coverings. This can cause a lot of problems.

Paper. They prefer starchy materials like paper and wood. Some reports suggest they have a preference for glazed paper that has a starchy coating or a glossy, smooth finish. They might eat some of your books and magazines.

Linens. Because silverfish like starch, any starched linens are prime food sources. They might eat your linens, curtains, furniture coverings, and anything made of silk or cotton.

Silverfish are as common as cockroaches in some states. It can be very difficult to manage an infestation and it’s usually best to use the following methods together for the best results.

Seal your food. Reduce food sources for the silverfish and keep all food sealed in airtight containers.

Vacuum regularly. Keep food in one area of the house only. Vacuum carpets, floors, and furniture regularly and clean up any food debris.

Dehumidify and get rid of water. Silverfish love humidity and water. Reduce water sources by using a dehumidifier in the basement. Keep showers, tubs, sinks, and your laundry room clean and dry. Use plastic sheeting on the ground in any dirt crawl spaces and attics.

Make sure your yard is properly landscaped to allow water to drain away from your house. Keep your house in good repair with good window seals and caulking in cracks.

Fill cracks. Silverfish lay eggs in cracks and crevices. Seal off any cracks in your home to stop them from laying eggs and from hatching.

Use dusts in uncommon areas. Dusts like diatomaceous earth, boric acid, and amorphous silica gel are insecticides. Sprinkle these in areas where you normally don’t go like crawl spaces and attics. You can spray dusts like boric acid into cracks. These dusts only work if they stay dry.

Use combination insecticides. Residual sprays like propoxur, chlorpyrifos, and bendiocarb can protect your house for up to 45 days. You can spray these in infected areas and follow up with pyrethrins. These are short-contact sprays that will irritate the bugs and send them into the residual spray. Focus on cracks and places where you often see the bugs.

Japanese cedar essential oil. This essential oil (Cryptomeria japonica) might help control silverfish.

Remember that insecticides are poisonous and toxic to the environment. Read the labels and follow directions closely. Keep any products away from children and pets. Contact a professional pest control company to help deal with major infestations.