Silverfish at home: causes, risks, and solutions for the whole family

Silverfish are small, silvery insects most commonly seen in bathrooms, kitchens, or near baseboards. Their sudden appearance causes anxiety and disgust in many people, but it is actually an important sign that the home's microclimate is out of balance.

Silverfish do not appear by chance. They come to places where the living conditions suit them:

• excessive humidity,

• dark and sheltered places,

• access to food.

If these three factors are present, silverfish can reproduce quickly and spread throughout the living space.

What are silverfish?

Silverfish (in Latin, Lepisma saccharina) are a very ancient species of insect that has existed on Earth for hundreds of millions of years. Their form has remained almost unchanged, demonstrating their great adaptability.

They resemble small silver fish, measuring about 8–15 millimetres in length. Their bodies are covered with fine scales that give them a metallic sheen. Long antennae and three tail filaments help them navigate their surroundings and move quickly.

Characteristic features:

• a silvery, scaly body,

• long antennae,

• three tail filaments,

• very fast movement,

• nocturnal activity.

During the day, silverfish hide in cracks and sheltered places, and at night they come out to search for food. Therefore, people often notice them unexpectedly when turning on the light.

Why silverfish appear in the home

The main cause is a disruption of the indoor microclimate. It is usually associated with excessive humidity and poor ventilation.

The most common reasons are:

• humidity above 60%,

• condensation on walls and floors,

• leaking pipes and plumbing fixtures,

• poor ventilation in the bathroom and kitchen,

• the presence of mould,

• old paper and cardboard,

• cracks and crevices in walls and floors,

• spread from neighbouring properties through pipes and ventilation.

When several of these factors occur at the same time, the likelihood of silverfish appearing increases significantly.

In apartment buildings, silverfish can spread throughout the building because they move easily through ventilation shafts and pipes. In detached houses, the basement or crawl space, where it is constantly damp, is a common source of the problem.

Where silverfish live and hide

Silverfish thrive in darkness and humidity. They choose places where they are not disturbed and where the temperature is stable.

Typical habitats:

• bathroom and toilet,

• kitchen (especially under the sink),

• behind the washing machine and refrigerator,

• under the bathtub and shower enclosure,

• under skirting boards,

• in cracks between tiles,

• storage rooms and basements,

• the crawl space beneath the floor in detached houses.

Their nesting sites are often located in places hidden from view. Therefore, it may seem that the insects appear “suddenly,” even though they have actually been living there for quite some time.

What silverfish eat

Silverfish have a very varied diet. They feed on organic substances containing sugar and starch.

They feed on:

• sugar and flour,

• grains and pasta,

• breadcrumbs,

• paper and cardboard,

• wallpaper and wallpaper paste,

• books and documents,

• mold,

• hair and skin debris,

• cotton fabrics.

Therefore, silverfish can damage not only food but also household property. Old books, paper folders, and wallpapered walls are especially attractive to them.

Are silverfish dangerous to humans

Silverfish do not bite or spread infectious diseases. They do not pose a direct health risk.

However, their presence causes indirect problems:

• damage to property (clothes, books, wallpaper),

• promoting the spread of mould,

• possible allergic reactions,

• discomfort at home,

• an indication of excessive humidity in the living space.

Therefore, the presence of silverfish indicates that the living environment needs improvement.

How to get rid of silverfish: a systematic approach

Effective control must be comprehensive. Simply killing individual insects will not produce lasting results if the underlying causes remain.

Main steps:

• reducing moisture,

• removal of food sources,

• sealing hiding places,

• use of safe products.

Reducing moisture

Moisture control is the most important step.

It is recommended to:

• ventilate rooms regularly,

• use ventilation in the bathroom and kitchen,

• install a dehumidifier,

• not leave wet towels lying around,

• repair leaking pipes,

• keep humidity at 45–50%.

Without this, chemical treatments are not effective in the long term.

Cleaning and hygiene

Cleaning helps remove silverfish food sources and reduce their numbers.

It is important to:

• remove crumbs and food scraps,

• keep food in sealed containers,

• discard old paper and boxes,

• wash the floors and baseboards,

• clean the areas under the sink and household appliances,

• remove mold.

Regular cleaning makes the home unsuitable for them.

Sealing cracks and crevices

Silverfish use cracks as hiding places and pathways.

It is advisable to seal:

• cracks in tiles,

• gaps around skirting boards,

• pipe penetrations,

• ventilation openings.

Silicone sealant and expanding foam are suitable for this purpose.

If there are children and animals at home

In that case, toxic substances must be avoided.

Safe methods:

• dehumidification,

• regular cleaning,

• sealing cracks,

• natural scents (lavender, citrus),

• non-toxic mechanical traps.

Chemical agents should only be used when children and animals are not in the room, and the room must then be thoroughly ventilated and wet-cleaned.

If the house has underfloor heating

Underfloor heating creates ideal conditions for silverfish beneath the tiles if humidity is high.

Recommendations:

• measure humidity with a hygrometer,

• keep it below 45%,

• check tile joints,

• replace the old grout,

• inspect the basement and crawl space,

• remove moisture from lower areas.

Often, moisture under the floor is the source of the problem.

Prevention

To prevent silverfish from returning, follow these simple rules:

• keep the home dry,

• clean regularly,

• store food in containers,

• seal cracks,

• ventilate the rooms,

• avoid the accumulation of paper and boxes.

Summary

Silverfish appear where there is moisture, darkness, and food. Their presence is not accidental but indicates problems with the home's microclimate. They can only be eliminated through a comprehensive approach combining moisture control, removal of hiding places, and sensible pest control.

Particular caution is needed in homes with children, animals, and underfloor heating. Proper prevention not only helps eliminate them but also makes the home healthier and more comfortable.