How Do You Get Rid of Silverfish?

In Summary: Silverfish (Lepisma saccharina) are wingless insects, 10 to 12 mm long and silvery-gray in color, that seek out moisture, warmth, and food. They do not bite or transmit diseases, but they damage paper, books, clothing, and dry goods. To eliminate them, reduce humidity, seal cracks with cement, and combine traps with an insecticide for crawling insects.

To get rid of silverfish, you have to take away what they seek most: moisture and food.

Reduce humidity in bathrooms and kitchens, seal cracks with cement (never with silicone, as they’ll eat it), and combine traps with an insecticide for crawling insects. If you see them repeatedly or they’re already damaging books, clothing, or merchandise, what will truly eliminate them is a professional treatment that targets the source of the infestation.

The silverfish, also known as the silverfish, is one of those typical damp-loving pests that can appear in your home unexpectedly. It doesn’t bite and isn’t dangerous to your health, but once infested, it can damage paper, textiles, and anything starched. Here’s how to recognize it, where it comes from, and what really works to get rid of it.

What are silverfish (or lepismas)?

Silverfish ( Lepisma saccharina ) are very ancient insects; in fact, they have been on Earth for millions of years, long before cockroaches. They belong to a group of primitive, wingless insects and move quickly, with a swaying motion reminiscent of a swimming fish. Hence their name.

Although their appearance is off-putting, they are not dangerous. They don’t bite, sting, or transmit diseases. The problem lies elsewhere: when they reproduce freely, they eat paper, clothing, and even the starch in bookbindings.

How can you recognize them by their appearance and size, and why are they called that?

Recognizing a sardine is easy when you know what to look for:

• Long and flattened body, wider at the head and tapering towards the tail.
• Silvery gray or bright color, with a very characteristic metallic reflection.
• They measure between 10 and 12 mm, not counting the antennae and the three tail appendages.
• They don’t fly, and they flee from light, so you almost always catch them at night or when you move something.

If you find irregular holes in stored clothes or small pieces of skin that are shedding, it’s a good sign that they’ve been around the house for a while.

Where do they come from and why do they appear in your house?

They come out looking for three things: humidity, warmth, and food. They need environments with high humidity, above 75%, and mild temperatures between 20 and 30 degrees Celsius. That’s why bathrooms, kitchens, laundry rooms, and basements are their favorite places.

They also enter from outside through cracks, drains, or inside cardboard boxes and old books you bring into your home. And be aware of this: a significant infestation is almost always a sign of a problem with dampness or mold, because silverfish also feed on fungi. If you have an infestation, it’s a good idea to check for any leaks or dampness you might be overlooking.

Do silverfish bite? Are they dangerous?

No, silverfish don’t sting or bite, and they’re not dangerous to people or pets. They don’t transmit diseases or have any venom, so you can rest assured about that.

What they do cause is inconvenience and material damage. When there are many of them, they contaminate stored dry goods and damage valuables. It’s not a health problem, but it is a preservation issue, especially if you store paper, files, or textiles.

What damage do they cause? Books, clothing, paper, and stored merchandise

The sardine eats practically anything containing starch, sugars, or cellulose. This is its typical shopping list:

• Paper, cardboard, and books, due to the starch in the cellulose and the glues used in the bindings.
• Clothing and natural fabrics such as cotton, linen or silk, especially if they have traces of sweat or food.
• Flours, cereals, sugar and other poorly sealed dry foods.
• Silicone from the joints, glues, skin fragments, hair and household dust.

In a home, the damage is usually annoying but manageable. The situation changes if you have an infestation in large libraries, archives, or businesses that store paper, packaging, or textiles, where an uncontrolled infestation can ruin merchandise and documents. That’s why it’s best to stop it early.

How to exterminate silverfish?

There’s no single magic formula. What works is attacking both the insect and the conditions that keep it alive. Let’s take it one step at a time.

Home remedies (and how well they actually work)

Before spending money, there are things you can try that help control low numbers:

• Lower the humidity. Ventilate the bathroom and kitchen daily, and use a dehumidifier or moisture-absorbing boxes in the most humid areas.
• Thorough cleaning. Vacuum corners, baseboards, drawers, and behind furniture to get rid of adults and eggs.
• Diatomaceous earth. A powder that damages the insect’s cuticle and dehydrates it. Sprinkle it in cracks and corners, following the label instructions.
• Sticky traps. They are used to catch those that roam at night and, above all, to know where they move.

They work to keep them at bay, but they have a clear limit: they can’t reach the hidden breeding grounds or the eggs inside cracks and false ceilings. That’s why you often see them disappear for a few days and then return.

Insecticides and traps: what do you buy at Mercadona or Leroy?

In supermarkets and large stores like Mercadona or Leroy Merlin, you can find sprays for crawling insects, insecticidal lacquers, and traps. To see if they’re useful, take a look at this:

• Choose an insecticide specifically for crawling insects, not just any mosquito repellent.
• Apply it where they really hide: baseboards, door frames, joints, and cracks, not in the middle of the floor.
• Always follow the instructions and ventilate the room after applying it.

They’re a temporary fix that works well for mild cases. The problem is that they only target the ones you see, not the ones reproducing inside the wall. If the infestation is large or recurs frequently, they won’t be enough, and you’ll have no choice but to seek professional help.

Professional treatment: when home remedies are not enough

When home remedies fail to solve the problem, or when there’s a risk to merchandise, files, or textiles, the most effective solution is a professional treatment that addresses the root cause.

How to prevent silverfish from returning? Prevention

Once you get rid of them, the idea is to make things difficult for them so they don’t come back:

• Keep the bathroom, kitchen, and laundry room well ventilated and as dry as possible.
• Seal cracks in walls, floors, and frames. Do it with cement, not silicone, because remember, they eat it away.
• Store clothes in tightly sealed bags and, if they are going to be stored for a long time, wash them before storing them.
• Seal flours, cereals, and sugar in airtight containers.
• Do not accumulate cardboard boxes, newspapers, or old books in damp or enclosed areas.
• Repair any water leaks as soon as possible. If you have dampness, call a professional to fix the problem at its source.