What are silverfish? Learn about these nocturnal household pests

Key points

• Silverfish can cause property damage but are not a threat to your health and safety.

• Silverfish are nocturnal, usually avoid humans and tend to congregate in humid areas of your home.

• A silverfish infestation is difficult to resolve without the help of pest control professionals.

Like earwigs and centipedes, silverfish are known in the pest industry as “occasional invaders” because they enter homes seeking more hospitable habitats than they can find outdoors. 

Homeowners taking a nighttime visit to the bathroom might spot a metallic creepy-crawly darting across the floor. Silverfish are common household pests, earning their moniker from their fish-like appearance and movement. These nocturnal, wingless insects propagate in humid areas of homes across America.

Silverfish infestations often result in property damage. They target the carbohydrates in paper products, such as books or wallpaper, and get into dry goods, such as oatmeal. While these pesky bugs might disturb your belongings or pantry, you don’t need to worry about your own health or safety. Silverfish don’t bite or transmit disease to humans. In fact, they’ll likely avoid you altogether.

Contending with a silverfish infestation is best left to pest control professionals, but you can take measures to ensure your home sweet home isn’t theirs.

How do you identify a silverfish infestation?

The signs of a silverfish infestation may be apparent before you notice the silverfish themselves. This is because silverfish are nocturnal and tend to avoid humans.

“Silverfish often infest homes to find food sources and shelter,” said Jim Fredericks, Ph.D., senior vice president of public affairs at the National Pest Management Association (NPMA). “They’re attracted to moisture and thrive in humid environments, which is why you can commonly find them in bathrooms, kitchens, basements and attics.”

Silverfish leave behind evidence of feeding on starchy materials in the form of small, irregularly shaped holes in clothing, books or wallpaper. You may see silverfish feces that look similar to black pepper. Silverfish also leave behind scales from molting or yellow stains from their excrement.

Silverfish, or lepisma saccharina, are bristletail insects about 3/4  inch long with a silvery, scaled body. These wingless insects have small compound eyes and long antennae in addition to three antennae-like appendages at the end of their body. 

They are expert crawlers, so you may even notice them on walls, skylights, roof soffits or ceilings. Their signature metallic bodies and darting movements will aid in identification.

If you suspect a silverfish infestation, inspect the areas of your home where they are most likely to congregate, including bathrooms, basements and attics. You will have the best luck finding them at night when they venture from their hiding places to feed. Remember that the location where you spot one silverfish may not be the locus of the infestation.

How do you get rid of silverfish in your home?

Eliminating a silverfish infestation requires a combination of efforts to both exterminate the insects and address the environment that attracted them in the first place. After identifying the infestation, discover whether it is localized to a certain area or widespread throughout your home. This helps to target your approach.

For immediate removal of silverfish bugs that you see, simply use a vacuum cleaner. While this reduces the population, you will likely need to employ other strategies to eliminate the infestation.

Manage the environment

Make your home an uncomfortable environment for silverfish to live. That means addressing humidity or dampness in your home and removing food sources.

Consider identifying and solving any plumbing problems or leaks. Use dehumidifiers and fans to promote a drier home. Additionally, ensure paper products, which are a favored source of food for silverfish, are stored in dry areas of your home.

Silverfish bugs feed on many different items in your home — including immovable parts of your home such as wallpaper or paint — making it difficult to completely eliminate their food sources. 

However, if you find silverfish damaging particular items in your home, do your best to make those items inaccessible. Try storing food items that attract silverfish in airtight containers, and use plastic bins with snapping lids for other storage.

Use insecticides

Insecticides are best saved for large and widespread infestations. When purchasing pesticides, look for labels that list synergized pyrethrin and pyrethroids such as bifenthrin, cyfluthrin, tetramethrin and phenothrin. These sprays will kill silverfish on contact and help reduce further escalation of the infestation.

With proper application, insecticides should eliminate infestations in two to three weeks. If you don’t see improvement, you may be treating the wrong area of your home.

Remember that silverfish insecticides only work in tandem with reducing moisture in the home. If you do not control humidity, the infestation will continue after using insecticides.

Choose natural methods

Those who prefer a more natural method than chemical pesticides should consider using essential oils. Japanese cedar oil is an effective silverfish repellent based on studies. Use it as a preventive measure or to manage an infestation.

While not as effective at killing the bugs as insecticides, a solution of cedar oil and water has been shown to kill a majority of silverfish and reduce activity when sprayed directly on or in the areas they are infesting.

Hire professionals

Managing a silverfish infestation on your own can be frustrating for many reasons. They are difficult to find, reproduce quickly and live for weeks without food or water.

Even if you remove their food sources and reduce humidity, silverfish may still linger in your home. Moreover, without knowing exactly where they are hiding out, repellants might only move them from one part of your home to another. That’s why it’s usually recommended to call in a professional.

Professional pest control companies understand how to get rid of silverfish infestations properly. “A licensed pest control professional will conduct a thorough inspection to identify the full extent of the silverfish infestation,” Fredericks said. “Once the situation is properly identified, the appropriate control measures can be taken.”

Why are silverfish a problem?

While silverfish do not threaten your family’s health or safety, they harm property and can even damage your home. The damage results from feeding as well as excrement staining. Silverfish can also get into easily accessible food such as flour or sugar.

Fredericks cautioned that silverfish infestations are difficult to eliminate and are best left to the professionals. Silverfish bugs are nocturnal and hide in hard-to-reach spaces, making them especially difficult to detect and eliminate. They can also live without food or water for several weeks at a time.

Are silverfish dangerous?

Generally, silverfish are not dangerous to humans as they do not bite or spread diseases. However, there is some evidence that silverfish can cause respiratory allergies in children.

The biggest impact you should worry about is on your home. Due to their nocturnal nature, silverfish infestations are not obvious and may go unnoticed for quite some time. This means that they cause substantial damage before they are ever discovered.

Why are silverfish infesting your home?

As occasional invaders, silverfish take shelter in your home for a safe place to live. This often occurs during fall as they seek a place to spend the winter, though they are found indoors during all seasons. Unfortunately, once they find a stable source of food — your stuff — they will stick around, especially if the environment remains humid.

The presence of silverfish can indicate that your home is overly humid. Silverfish thrive in habitats that are 70 to 80 degrees Fahrenheit with a relative humidity of 50% to 75%.

Silverfish habits

Silverfish bugs enter your home from outside or are carried in on already-infested items, such as secondhand furniture. Their small, flat bodies allow entry to your home through gaps or cracks, including those around doors, windows and crawl spaces.

Silverfish are very agile. They move rapidly, shuffling sideways across the floor or easily crawling up walls. They are good at finding hiding spots in cracks or crevices.

Silverfish congregate in areas commonly used for storage, including basements and attics. Here, they find a great snack in cardboard boxes and stored paper. They also feed on many other items in your home made of carbohydrates. Common culprits include book bindings, cereal, fabric, products with glue and decaying wood. In addition to consuming these items, they also eat other dead insects.

Silverfish bugs multiply quickly, producing more than 50 offspring in their three-year life span. Mature females lay three eggs a day. “They will breed in a variety of areas, including wall voids in and under the subflooring and attics,” Fredericks said. This adds to the difficulty of removing infestations.

How do you prevent silverfish in your home?

The best way to prevent a silverfish infestation is to keep your home dry. Before taking any action, assess the humidity of your home. Common home thermometers often include a hygrometer or a tool that measures the amount of water vapor in the air. This will help you understand which areas of your home to address.

Keep in mind that the humidity in your home will change through the seasons. Depending on where you live, winters may tend to be drier than summers. You should shoot for a humidity of 30% to 50%.

Equip humid areas of your home, including bathrooms, basements and attics, with fans or dehumidifiers. Don’t forget to turn on the bathroom fan when you shower and empty dehumidifiers containing a retention tank.

What’s next?

Once you suspect a silverfish infestation in your home, you should act fast to prevent additional damage. By the time you notice the infestation, damage has likely already occurred.

There are products on the market to combat infestations, but you will have the best results by hiring pest control professionals who know how to eliminate an infestation. “The NPMA does not recommend handling silverfish infestations on your own,” Fredericks said. “Pest control professionals have the knowledge and tools to efficiently and thoroughly identify and treat infestations.”

While professionals handle the infestation, you should address the humidity that attracts the silverfish. Recurring or sustained dampness may allow an infestation to linger despite the best pest control efforts.

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