Every spring, I become a little more aware of everything happening around my house.
The weather warms up.
The insects return.
Small animals become active again.
And, eventually, I start thinking about snakes.
I don’t particularly enjoy the idea of finding one near my house, and the crawl space underneath the house seemed like exactly the kind of dark, sheltered place where a snake might decide to hide.
So I started looking for a simple way to discourage them from going underneath the house.
That’s when I remembered something I had heard for years:
Mothballs supposedly keep snakes away.
The idea seemed almost too simple.
Put mothballs around the crawl space, and the strong chemical smell would supposedly make the area unpleasant enough that snakes would stay away.
So this spring, I decided to try it.
I put mothballs in the crawl space and waited.
What happened next wasn’t the snake-repelling success story I expected.
Instead, I learned that this commonly repeated household trick has a much bigger problem than whether or not it works.
The First Thing I Noticed Was the Smell
The smell was impossible to ignore.
Mothballs are designed to release pesticide vapors over time. Depending on the product, the active ingredient may be naphthalene or paradichlorobenzene.
That strong odor isn’t simply a harmless “snake smell.”
It is the smell of a pesticide vaporizing into the surrounding air.
And that’s where my experiment immediately became more concerning.
A crawl space isn’t an outdoor flower bed.
It’s part of the structure of the house.
Air from a crawl space can potentially move through cracks, gaps, ductwork, plumbing penetrations, or other openings into the living areas above.
The EPA specifically identifies misuse of mothballs in places such as crawl spaces and air-handling systems as a form of pesticide misuse and notes that accidental exposures to mothball products are a concern.
Suddenly, I wasn’t thinking only about snakes anymore.
I was thinking about the air inside my house.
Then I Discovered Something Important
The biggest surprise was finding out that mothballs aren’t actually registered as snake repellents.
This isn’t simply a matter of whether Grandma’s trick works better than modern products.
Mothballs are pesticides, and their labels specify how they are supposed to be used.
The University of Georgia Extension specifically warns that mothballs are not registered for use as snake repellents and says they are ineffective for that purpose.
That completely changed how I looked at my experiment.
I had assumed:
“If it smells terrible to me, surely snakes will hate it even more.”
But that’s not how pesticide effectiveness works.
A strong smell doesn’t automatically make something an effective animal repellent.
And something being unpleasant doesn’t mean it’s safe or legal to use as a repellent.
Why the Myth Seems So Believable
It’s easy to understand why this idea became popular.
Mothballs have an incredibly strong odor.
They’re specifically designed to release vapors.
And snakes have a reputation for being sensitive to smells.
So the logic seems straightforward:
Strong smell + snake = snake leaves.
The problem is that real-world snake control doesn’t work that simply.
Extension guidance says there are no reliable chemical repellents for snakes, and mothballs aren’t labeled for that use.
In other words, putting more mothballs around the crawl space doesn’t necessarily mean you’re creating a stronger snake barrier.
You may simply be creating a stronger pesticide exposure.
The Mothballs Didn’t Create an Invisible Snake Wall
This was another important realization.
I had imagined the crawl space becoming an unpleasant zone that snakes would refuse to enter.
But there was no guarantee of that happening.
A snake doesn’t look at a pile of mothballs and think:
“That area is chemically protected. I’ll find somewhere else.”
If the crawl space provides shelter, prey, moisture, or a convenient entrance into the house, those factors may matter much more.
That’s why physical exclusion is such an important part of dealing with unwanted wildlife.
Instead of trying to make an area chemically unpleasant, it makes more sense to make the area physically inaccessible.
What I Should Have Done Instead
The better strategy would have been to figure out why a snake would want to enter the crawl space in the first place.
Snakes aren’t usually interested in a house simply because it’s a house.
They’re looking for the things that help them survive.
That can include:
- Shelter
- Hiding places
- Moisture
- Warm or cool protected areas
- Prey such as rodents
- Gaps that provide easy access
So if you want fewer snakes around your home, start with the conditions around the house.
Don’t start by throwing chemicals into the crawl space.
Step One: Look for Entry Points
One of the most useful things I could have done was inspect the crawl space itself.
Look around the foundation.
Check vents.
Inspect gaps around pipes.
Look for openings around utility lines.
Examine damaged screens.
Look for spaces underneath doors or other access points.
A snake doesn’t need a giant hole.
If there is an opening large enough for a snake to enter, it can potentially become an access route.
The goal isn’t to create a poisonous or unpleasant environment.
The goal is to keep the snake from getting inside in the first place.
Step Two: Make the Area Less Attractive
The University of Georgia Extension recommends removing debris and potential hiding places around homes because piles of leaves, wood, and other materials can provide habitat for snakes and the animals they eat.
That means a little spring cleanup can be more useful than an entire bag of mothballs.
Remove unnecessary piles of:
- Wood
- Leaves
- Construction debris
- Boards
- Cardboard
- Dense vegetation
- Other clutter
A clean perimeter gives snakes fewer convenient hiding places.
Step Three: Think About Rodents
This was another thing I hadn’t considered enough.
If a property has mice or other small prey animals, it may also attract predators.
A snake that finds an area with food has a reason to stay.
So if you’re worried about snakes around a crawl space, don’t focus exclusively on the snake.
Look at the entire food chain.
Are there mice?
Are there rats?
Are there frogs?
Are there insects?
Is there standing water?
Are there piles of material where prey animals can hide?
Sometimes solving the underlying attraction is much more effective than trying to repel the snake directly.
The Safety Problem With Mothballs
This is where the experiment stopped being funny.
Mothballs aren’t ordinary air fresheners.
They are pesticide products.
The EPA says pesticide labels are legally enforceable and that using a pesticide in a manner inconsistent with its labeling violates federal law in the United States.
Current EPA-approved mothball labels specify uses such as protecting clothing from clothes moths in clean, airtight containers or storage spaces. One current label, for example, specifically describes use in airtight containers and warns that the product must not be placed where children or pets can access it.
A crawl space being underneath a house doesn’t automatically make it an appropriate place to use mothballs.
The product label matters.
And if the label doesn’t authorize using the product to repel snakes in a crawl space, that isn’t an appropriate use.
“But It’s Under the House, So Nobody Can Touch It”
That might seem reassuring.
But physical contact isn’t the only concern.
Mothballs work by releasing vapors.
The EPA notes that moth repellents can pose inhalation concerns and recommends minimizing exposure to their vapors.
A crawl space may be poorly ventilated.
That can make chemical vapor accumulation particularly concerning.
And because the crawl space is physically connected to the house, it’s not something I’d treat as completely separate from the indoor environment.
What About Children and Pets?
This is another reason the experiment isn’t worth repeating.
Mothballs can be dangerous if swallowed, and the EPA specifically warns about risks to children and pets.
A crawl space might seem inaccessible.
But homes change.
Pets can sometimes get into unexpected spaces.
Children can discover access doors.
Maintenance workers may enter the area.
A mothball that has been forgotten for months can become a future exposure hazard.
That’s a terrible trade-off for a snake-control method that isn’t reliably effective.
What Happened to the Snakes?
Here’s the frustrating part.
I couldn’t honestly say:
“The mothballs worked.”
Even if I didn’t see a snake afterward, that doesn’t prove the mothballs repelled one.
Maybe there simply wasn’t a snake.
Maybe it entered somewhere else.
Maybe weather conditions changed.
Maybe prey availability changed.
Maybe the snake moved naturally.
That’s an important lesson with home pest-control experiments.
Absence isn’t proof of effectiveness.
If you put something down and don’t see a pest afterward, it’s tempting to give the product credit.
But without knowing whether the pest was actually there in the first place, you can’t determine whether the treatment worked.
The Strong Smell Wasn’t Proof of Success
At first, I thought:
“If I can smell the mothballs, a snake definitely can too.”
That sounds convincing.
But even if an animal detects an odor, that doesn’t establish that the odor will reliably cause the animal to leave.
The University of Georgia Extension specifically says mothballs do not repel snakes and describes their use for this purpose as ineffective.
So a powerful smell should not be confused with an effective repellent.
What I Did With the Mothballs
If you’ve already placed mothballs in a crawl space, don’t simply keep adding more.
The safest approach is to stop using them for this purpose and follow the product label’s disposal instructions.
Don’t dump them outdoors.
Don’t put them down drains.
Don’t burn them.
Don’t bury them.
Don’t move them into another unauthorized location.
The EPA recommends disposing of unwanted pesticides according to their label directions and keeping pesticides in their original containers.
If you’re unsure how to handle a specific product, contact the appropriate local hazardous-waste or pesticide authority and provide the product name and active ingredient from the label.
Don’t Sweep the Mothballs Around
Another temptation might be to spread the mothballs throughout the crawl space to “cover” more area.
Don’t.
Using more pesticide doesn’t automatically mean better pest control.
The EPA specifically warns that increasing pesticide amounts doesn’t provide more protection and can increase risks to people and pets.
If the product isn’t approved for the intended use, increasing the quantity only makes the misuse more serious.
What Actually Makes a Crawl Space Less Appealing to Snakes?
The answer is much less exciting than a bag of magic pellets.
It’s mostly maintenance and exclusion.
Keep vegetation around the structure under control.
Remove debris.
Address rodent problems.
Reduce unnecessary hiding places.
Repair damaged screens.
Seal appropriate openings.
Manage moisture problems.
Keep the area around the foundation tidy.
And inspect the crawl space periodically.
These steps don’t promise that you’ll never see a snake.
But they address the conditions that can make the area attractive.
What If You Actually Find a Snake?
This is another situation where panic can make things worse.
Don’t corner it.
Don’t try to grab it.
Don’t try to kill it.
Many snake bites happen when people attempt to handle or kill snakes.
If you don’t know what species you’re dealing with, keep your distance and arrange for appropriate local wildlife or pest-control assistance.
A snake that is simply passing through is very different from a snake that has established itself in a structure.
The solution should depend on the situation.
Why Physical Exclusion Beats a “Snake Repellent”
Imagine two different strategies.
Strategy one says:
“Put something unpleasant in the crawl space and hope the snake doesn’t like it.”
Strategy two says:
“Find the opening and close it so the snake can’t get inside.”
The second strategy addresses the actual access problem.
That’s why exclusion is such a valuable part of wildlife management.
You aren’t trying to convince an animal that your home isn’t attractive.
You’re preventing it from entering.
Frequently Asked Questions
Do mothballs keep snakes away?
No reliable evidence supports mothballs as an effective snake repellent. University of Georgia Extension specifically states that mothballs are not registered for snake control and are ineffective for that purpose.
Can I put mothballs in my crawl space?
You should not use mothballs in a crawl space to repel snakes unless the specific product label expressly authorizes that use. EPA emphasizes that pesticide labels are legally enforceable and that products must be used according to their labeling.
Why do mothballs smell so strong?
Mothballs are designed to release pesticide vapors. Depending on the product, the active ingredient can include naphthalene or paradichlorobenzene.
Are mothballs dangerous to pets?
They can be. The EPA warns about mothball hazards, including risks from exposure and ingestion, particularly for children and pets.
What should I do if I already put mothballs in my crawl space?
Stop using them as a snake repellent. Don’t add more. Follow the product’s disposal instructions or contact the appropriate local hazardous-waste or pesticide authority for advice on safely removing and disposing of the product.
What’s a better way to keep snakes out?
Focus on exclusion and habitat management: inspect and repair entry points, remove debris and hiding places, manage rodents and other prey, and keep the area around the structure maintained. Extension guidance recommends these kinds of measures rather than relying on mothballs.
Will more mothballs work better?
No. Increasing the amount of a pesticide doesn’t automatically make it more effective and can increase exposure risks.
The Bottom Line
I started this spring with a simple goal:
Keep snakes out of my crawl space.
I thought mothballs would provide an easy solution.
Instead, the experiment taught me that some of the most persistent household pest-control tricks are persistent precisely because they sound logical.
Mothballs smell incredibly strong.
Snakes are animals that encounter smells.
Therefore, it seems reasonable to assume that mothballs should repel snakes.
But that conclusion doesn’t hold up.
University of Georgia Extension specifically says mothballs are not registered for snake control and don’t work as a reliable snake repellent.
And because mothballs are pesticides, using them in an unauthorized location such as a crawl space can create unnecessary exposure risks and, in the United States, may violate pesticide-label requirements.
The better lesson is much simpler:
Don’t try to poison, fumigate, or chemically repel your way out of a wildlife problem when exclusion can address the actual cause.
Inspect the crawl space.
Find the openings.
Remove unnecessary hiding places.
Deal with rodents and other prey.
Keep the foundation area maintained.
And if a snake has already gotten inside, give it space and get appropriate help rather than confronting it yourself.
What started as an attempt to keep snakes away ultimately taught me something more useful:
Sometimes the safest pest-control trick is the one you don’t try.
A bag of mothballs might seem like an inexpensive solution, but when the product isn’t designed or labeled for the job, the smell isn’t worth the risk—and it certainly isn’t proof that the snakes will stay away.