Why Are Silverfish Harmful?

For all the talk about cockroaches being on Earth forever, silverfish are the actual oldest known insect species to still crawl on our planet. What are its relations to people, however? Are silverfish harmful to humans or are silverfish harmless? If cockroaches can spread diseases and other insects feed on human blood and skin, can silverfish too be dangerous to humans?

The short answer is – generally, no. But silverfish are still considered a nuisance pest and bring several notable negatives with them, so let’s explore those in detail.

Do silverfish pose any health risks?

Silverfish are not blood-sucking parasites like a lot of the creepy-crawlies we sometimes find in our homes. Instead, they prefer a diet of carbohydrates, sugars, starches, and cellulose. As such, their preferred targets in our homes are wood and paper products, as well as bread, dry seeds, and nuts, as well as other dry foods.

So, do silverfish spread any diseases? And the truth is that..

there is zero evidence of silverfish spreading bacteria or viruses in any way. Silverfish can, however, spread other contaminants. As silverfish tend to crawl in a lot of places, including trash cans and bathrooms, it’s not impossible for a silverfish to pick up something from the trash and spread it over your food supply as it walks over it.

Yet, this isn’t a common occurrence and isn’t specific for silverfish. Any other insect such as ants, for example, that traverses both food and trash can do the same.

Okay, so silverfish don’t pose any serious health risks. But do silverfish bugs bite?

The answer is no again. They feed on neither human blood nor our flesh. Silverfish might nibble on human hair and dandruff which is why you can find them crawling around your hairbrush or your bed. In rare – and creepy – cases you can wake up to silverfish crawling on your pillow or even on your scalp if you happen to have enough dandruff. They will not bite you, however.

Silverfish are also neither poisonous nor venomous as they don’t need such weapons for hunting or for defense. So, if you’re worried about whether can silverfish hurt you or are silverfish harmful to cats or dogs, the answer is no. And although silverfish and earwigs both have the reputation of crawling in people’s ears and laying their eggs there, this is completely unfounded and is an urban myth born from how uncomfortable people are with these bugs’ body shapes. If a silverfish bug is snooping around your pillow for dandruff it can, theoretically, crawl on top of your ear for a second, but nothing more.

Can silverfish trigger or cause allergies?

Silverfish, can, however, cause allergies. And this is one of the main types of health-related silverfish damage you should keep in mind.

Silverfish molt their external shell frequently and if it isn’t cleaned it can become part of your household dust.

Once this happens and the silverfish remnants get inhaled, they can cause an allergic reaction similar to other insect and dust related allergies. There are various studies on PubMed that examine the problem of silverfish allergies, however, so far it isn’t as well documented as other pest allergies as it isn’t that common.

Can silverfish damage your property?

A much more notable answer to the question of why are silverfish bad is that they can damage our homes and property.

While silverfish can consume wallpapers and even wood, they are, however, practically incapable of causing the same levels of structural damage to your walls and home that termites or carpenter ants are. Silverfish reproduce very slowly and don’t consume as much food, so for any significant structural damage to appear in your home’s walls or foundations, the home will need to be abandoned by humans and overrun by an impractically large number of silverfish. If that’s the case, then the structure will have other, much more significant problems at that point, than silverfish.

As silverfish feed on carbohydrates, sugars, starches, and cellulose, silverfish can often be found nibbling on our books, old photos or documents. One of the most common ways people find out that they have silverfish is by finding silverfish droppings or live silverfish in their books or photo boxes/albums. Silverfish poop in old books is unnerving, but finding a living silverfish in the book by your nightstand is especially freaky, particularly late at night. If you have silverfish in your home, the first thing you want to do before you start exterminating them is to make sure that your vital documents, books, and photos are protected in sealed plastic bags. Also, pay attention to your walls and wallpapers.

And in their hunt for food silverfish will also often pay attention to some of your linens and cotton clothes as well. As a result, you can often find silverfish holes in clothes, as well as poop stains. Particularly if you’ve left a lot of clothes cluttered around the home, gathering dust, you can expect the find silverfish in them after some time.


Silverfish are among the most fascinating and creepy insects that you can find in your home but they are not the most dangerous ones. They can feed on the paper in your books documents and family photos, they can cause minor allergic reactions, or they can, in rare cases, transfer dirt and contaminants from your trash can to your food storage units, but they don’t bite or spread any diseases on their own. They reproduce very slowly and gradually which makes dealing with them in time easier, but they can still cause some unpleasant damage to some items in your home if left unchecked.


Dawn Wall

I live in Denmark. 6 weeks ago I flushed a silver fish out of my left ear after 3 days if discomfort and cracking noises in the ear.
Only 2 weeks later my boyfriend awoke with a start in the middle of the night with a silver fish entering his ear! He rushed to rinse it out immediately and succeeded. I do have a few in the house but it is far from an infestation. It is as if they are literally targeting the ear canals.


    This isn’t considered to be a usual behavior. Even though there are stories about people who have had this happen to them, silverfish don’t really have any ear-specific interests. As disturbing as it must have been for you and your boyfriend, it’s also quite fascinating to hear about someone having experienced it twice in such a short period of time.

Crystal Lynn Goble

I just pulled a silverfish out of my ear this morning. I was having crackling and then pain in my ear and pulled it out. Very disturbing, which led me to research and landed on your site.

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