Yes, mothballs do kill moths, but only when used correctly. The key requirement most people miss: mothballs must be placed in an airtight, sealed container to work. Tossing them loosely in a closet or dresser drawer won’t build up enough toxic vapor to kill anything. It’ll just expose you and your family to a pesticide.
How Mothballs Actually Work
Mothballs contain one of two active chemicals: naphthalene or paradichlorobenzene. Both are solid at room temperature but slowly release a gas as they dissolve. When that gas builds up inside a sealed container, it reaches a concentration high enough to be lethal to clothes moths and their larvae. The fumes damage cells and tissues in the insects, killing them over time.
This is why the airtight container is non-negotiable. In an open closet, the vapors simply disperse into the room. They never reach a lethal concentration for moths, but they do reach a level that can make you sick. When you smell mothballs, you are literally inhaling a pesticide.
It’s the Larvae That Eat Your Clothes
Adult moths don’t actually damage fabric. The two species responsible for most clothing damage are the webbing clothes moth and the casemaking clothes moth, and in both cases, it’s the larvae that feed on natural fibers like wool, silk, and cashmere. The damage shows up as thinned areas or small holes where larvae have grazed on fibers.
This matters because killing the flying adults you spot in your closet doesn’t solve the problem. The eggs and larvae hiding in your stored clothing are the real threat. Mothballs in a properly sealed container can kill all life stages, but only if the vapors reach sufficient concentration and stay there long enough.
The Health Risks Are Real
Naphthalene, the more common active ingredient, is classified as a possible human carcinogen by both the EPA and the World Health Organization. The immediate effects of breathing in too much vapor include headaches, nausea, dizziness, and vomiting.
At higher exposures, naphthalene causes hemolytic anemia, a condition where red blood cells break apart and can no longer carry oxygen properly. People with a certain inherited enzyme deficiency (called G6PD deficiency, which affects roughly 400 million people worldwide) are at much greater risk. Kidney and liver damage can also occur.
Infants are particularly vulnerable. Clothing, blankets, and diapers stored with mothballs and not washed before use have caused anemia in babies. Pregnant women who inhaled mothball vapors or ingested mothballs gave birth to babies with hemolytic anemia.
How to Use Them Correctly
Mothballs are EPA-regulated pesticides, and using them in any way not specified on the label is actually illegal. The correct method is straightforward:
- Seal the container. Place mothballs with your clothing inside a tightly closed, airtight container like a storage bin with a gasket seal, a garment bag you can zip completely shut, or a trunk that closes tightly. A regular closet does not count.
- Keep them away from living spaces. The container should prevent fumes from accumulating in rooms where people or pets spend time.
- Never use them near food. Mothballs should not be placed anywhere near food storage or preparation areas.
- Wash everything before wearing. Any clothing stored with mothballs needs to be laundered or dry-cleaned before you or anyone in your household wears it.
Using mothballs outdoors to repel snakes, insects, or other animals is both illegal and harmful. They can contaminate soil, plants, and water, and pose a poisoning risk to children, pets, and wildlife. Some mothballs sold online or at discount stores are illegally imported products that haven’t been evaluated for safety, so their contents and risks are unknown.
Alternatives That Don’t Involve Pesticides
Pheromone traps are one of the most practical non-toxic options. These traps use a synthetic version of the scent female moths produce to attract males. Males fly to the trap and get stuck on a sticky surface. With fewer males available to mate, the population drops over time. Each trap stays active for about 12 weeks. For best results, place them at a height of three to six feet (the typical flight height of male moths), in quiet, dark, low-traffic areas where moths prefer to be. If placing a trap inside a closet, make sure garments aren’t packed so tightly that air can’t circulate around the trap.
Pheromone traps alone won’t eliminate a serious infestation. They work best as part of a broader approach: vacuuming regularly (especially along baseboards and inside closets), washing or dry-cleaning clothes before storing them, and keeping stored garments in sealed bags or containers. Cedar blocks and chips can repel moths to some degree, though their oils fade over time and they’re better at deterring moths than killing an established colony.
Freezing is another chemical-free option. Placing infested garments in a sealed plastic bag and leaving them in a household freezer for at least 72 hours kills moths, larvae, and eggs. Heat works too: a dryer on high heat for 30 minutes will destroy all life stages on items that can tolerate it.