You turn on the bathroom light late at night and notice something moving quickly across the floor.

It is small, silvery, and strangely shaped, with a tapered body and tiny bristles at the back. Before you can get a closer look, it disappears beneath a cabinet or slips into a crack.

If you've experienced this, you may have encountered a silverfish.

Silverfish are among the most common insects found indoors, particularly in damp, dark, and relatively undisturbed areas. Their unusual appearance can make them seem alarming, but the good news is that silverfish are not generally considered dangerous to people or pets.

Still, finding them repeatedly in your home is something worth paying attention to.

Their presence can sometimes indicate excess moisture, humidity, hidden leaks, or an environment that provides plenty of food and shelter.

So what exactly are silverfish, why are they appearing in your house, and what can you do about them?

Let's take a closer look.

What Exactly Is a Silverfish?

Silverfish are small, wingless insects recognized by their silvery-gray appearance and elongated, flattened bodies.

Their scientific name is Lepisma saccharinum.

They are called silverfish because of two distinctive characteristics:

Their silver-colored scales

and

their fish-like, wiggling movement.

Adult silverfish are typically around 12–19 millimeters long, although their size can vary.

They have three long, tail-like appendages at the rear of the body and long antennae at the front.

Despite their somewhat intimidating appearance, silverfish aren't aggressive insects.

They don't sting.

They don't bite people under normal circumstances.

And they aren't known for transmitting diseases to humans.

Their main concern is that they can become household pests when populations grow.

Why Do Silverfish Come Inside?

Silverfish generally prefer environments that are:

• Damp

• Humid

• Dark

• Cool or moderately warm

• Undisturbed

That's why they are frequently discovered in places such as:

Bathrooms

Basements

Laundry rooms

Kitchens

Attics

Closets

Storage areas

They can hide behind furniture, beneath sinks, around pipes, inside wall voids, and in cracks or gaps.

If you've recently started seeing silverfish, take a look at the environment around where you found them.

The insect itself may not be the main problem.

The conditions attracting it may be.

Humidity Is One of the Biggest Clues

Silverfish thrive in humid environments.

A home with persistent moisture provides the kind of conditions they prefer.

This can happen because of:

• Poor bathroom ventilation

• Condensation

• Plumbing leaks

• Damp basements

• Roof leaks

• Wet crawl spaces

• High indoor humidity

• Poorly ventilated storage areas

If silverfish are appearing regularly, checking the humidity and moisture levels in your home is a sensible first step.

You don't necessarily need to panic.