The advice to scatter mothballs around the perimeter of a home to keep snakes away is deeply embedded in rural folklore, but it does not hold up to scientific review. Understanding why and what actually influences snake behavior around structures is more useful than any repellent product on the market.
Why Mothballs Do Not Work
Mothballs contain naphthalene or paradichlorobenzene, chemicals that are effective against clothes moths in sealed storage containers, where the vapor concentration can reach levels high enough to be toxic to small insects. In open outdoor environments, the vapor disperses immediately and never reaches concentrations that affect snake physiology or behavior.
Multiple controlled studies examining snake response to naphthalene have found no consistent avoidance behavior. Snakes lack the olfactory complexity of mammals and do not respond to chemical irritants the way a dog or cat might. They sense the environment primarily through the Jacobson's organ and heat-sensing pits, not through a mammalian-type nose.
Common Ineffective Repellents
- Mothballs (naphthalene/paradichlorobenzene): No scientific evidence of effectiveness as snake repellents.
- Sulfur powder: No consistent scientific evidence.
- Cedar chips: No evidence of effectiveness.
- Cinnamon oil or clove oil: May cause temporary irritation but no lasting avoidance.
- Lime or diatomaceous earth: Not effective deterrents for snakes.
What Actually Influences Whether Snakes Use Your Property
Snakes are present where habitat conditions suit them. Changing those conditions is far more effective than any chemical product.
- Remove food sources: Mice attract rat snakes and copperheads. Eliminating the rodent population removes the primary reason snakes investigate structures.
- Eliminate harborage: Wood piles, rock piles, deep leaf litter, and dense ground cover directly adjacent to the foundation provide snake habitat. Moving these features away from the house reduces encounters significantly.
- Seal entry points: Structural exclusion, closing gaps under doors, filling foundation cracks, installing crawlspace vent screens, is the only reliable method for keeping snakes out of a structure.
- Mow the perimeter: Short grass around the foundation reduces concealment and discourages snakes from traveling close to the structure.
A Note on Mothball Safety
Beyond being ineffective, mothballs used outdoors are an environmental concern. Naphthalene is a recognized carcinogen that leaches into soil and groundwater. Mothballs placed in garden beds or around foundation planting are technically an improper use of a pesticide under federal law (FIFRA). It is worth noting this not to alarm homeowners but to clarify that the remedy creates real problems while solving none.
