Mothballs have one job: killing clothes moths and their larvae in sealed storage containers. That’s it. Despite widespread use as snake repellent, rodent deterrent, and general pest control, mothballs are a registered pesticide designed exclusively to protect stored fabrics from moth damage. Most of the ways people actually use them are both ineffective and illegal.
How Mothballs Actually Work
Mothballs contain either naphthalene or paradichlorobenzene, both of which slowly convert from a solid into a gas through a process called sublimation. As the mothball shrinks over time, it releases toxic fumes. When those fumes build up to a high enough concentration inside a sealed container, they kill clothes moths, their eggs, and their larvae.
The key word is “sealed.” Mothballs only work when the gas concentration reaches lethal levels, and that only happens in an airtight space. Tossing a few mothballs into an open closet or dresser drawer lets the vapors drift away before they reach a concentration that kills anything. You’re just breathing pesticide fumes for no benefit.
What They Protect Against
Clothes moths are the specific target. Two species cause most of the damage to stored fabrics: the webbing clothes moth and the casemaking clothes moth. It’s not the adult moths eating your wool sweaters. The larvae do the damage, feeding on natural fibers like wool, silk, cashmere, fur, and feathers. They can also attack blended fabrics if natural fibers are present.
Mothballs placed in an airtight garment bag, sealed plastic bin, or trunk with clothing you won’t wear for months can prevent larvae from destroying those items. This is the labeled, legal, and effective use of mothballs.
Why Using Them Outdoors Is Illegal
Scattering mothballs around your yard to repel snakes, squirrels, deer, or rodents is one of the most common misuses, and it’s against federal law. Mothballs are a regulated pesticide, and using them in any way that contradicts the label instructions is a violation of pesticide regulations. The Clemson University Department of Pesticide Regulation has specifically urged homeowners to stop using mothballs outdoors after receiving numerous complaints about the practice.
Beyond legality, it doesn’t even work well. While some granular snake repellents contain naphthalene (the same active ingredient), they use much lower concentrations and are formulated differently. Mothballs exposed to open air lose their chemical potency within days to weeks depending on wind and temperature. In a closet with limited airflow, they last roughly six to nine months. With regular air currents outdoors, the chemical dissipates in two to three months, long before it would meaningfully repel anything.
Health Risks of Improper Use
Mothball fumes aren’t just unpleasant. They’re genuinely toxic. The CDC documented a case in Indiana where a woman, her four-year-old daughter, and seven relatives across multiple households all developed symptoms from extensive indoor mothball use. They experienced headaches, nausea, vomiting, abdominal pain, confusion, anemia, and kidney problems. When the mothballs were removed, the symptoms resolved.
Prolonged inhalation of naphthalene can cause skin and eye irritation, gastrointestinal distress, neurological symptoms like confusion and convulsions, kidney damage, and severe anemia. People with a common genetic enzyme deficiency (affecting roughly 400 million people worldwide) are especially vulnerable to red blood cell destruction from naphthalene exposure.
Children are at particular risk because they may mistake mothballs for candy. Even a single mothball can be dangerous if swallowed.
Dangers to Pets
Dogs and cats can be poisoned by chewing on mothballs or inhaling fumes in poorly ventilated spaces. Of the three chemicals used in mothballs, camphor is the most toxic to animals, followed by naphthalene, then paradichlorobenzene. Early signs in pets include vomiting, loss of appetite, and abdominal discomfort. Larger exposures to naphthalene-based mothballs can progress to anemia, difficulty breathing, pale gums, tremors, and seizures. Paradichlorobenzene products tend to cause lethargy, weakness, and with chronic exposure, liver and kidney damage.
Using Mothballs Correctly
If you do use mothballs, the rules are straightforward. Place them inside a container that seals completely: a zippered garment bag, airtight plastic storage bin, or cedar chest with a tight-fitting lid. The clothing should be clean before storage, since moth larvae are especially attracted to fabrics stained with sweat, food, or body oils. Keep the sealed container in a space away from living areas, and don’t open it frequently, as this releases accumulated vapors and reduces effectiveness.
When you eventually open the container, air the garments out thoroughly before wearing them. The smell clings to fabric and takes time to dissipate.
Safer Alternatives
Cedar is the strongest natural moth deterrent. Cedar oil disrupts the pheromones clothes moths use to find mates and nesting sites, and female moths avoid the scent. Cedar blocks, rings, or sachets placed in closets and drawers offer ongoing protection without toxic fumes. The oil does lose potency over time, but lightly sanding cedar blocks or refreshing them with cedar essential oil restores their effectiveness.
Lavender oil also repels clothes moths, though its scent fades within about a week. Combining lavender with cedar or lemon oil extends how long it lasts. Other options include rosemary, thyme, mint, and bergamot essential oils. None of these kill an active infestation the way mothballs can, but they’re effective at prevention, particularly when combined with regular cleaning and proper storage habits.
For active infestations, washing or dry-cleaning affected garments and freezing items for at least 72 hours kills larvae and eggs without chemicals.
How to Dispose of Mothballs Safely
Unused or partially dissolved mothballs count as household hazardous waste. Don’t throw them in the regular trash or flush them down the toilet. Many communities run collection programs for hazardous household chemicals, either year-round drop-off sites or periodic collection events. You can search for options near you through the EPA’s Earth911 database by entering your zip code, or by contacting your local solid waste agency.