Mothballs contain high concentrations of one of two chemicals: naphthalene or paradichlorobenzene. Both are solid pesticides that slowly release toxic fumes designed to kill clothes moths and fabric-eating larvae. Despite their old-fashioned reputation, mothballs are federally regulated pesticides with real health risks for people, pets, and the environment.
The Two Chemicals in Mothballs
Every mothball sold in the United States is built around one active ingredient. Naphthalene is the older, more traditional chemical, derived from coal tar or petroleum. Paradichlorobenzene is a newer alternative considered somewhat less toxic to humans, though still harmful. Both are white, solid substances with strong, distinctive odors. You can often tell them apart by smell alone: naphthalene has a sharp, tar-like scent, while paradichlorobenzene smells sweeter, almost chemical-clean. Check the product label to see which one you’re dealing with.
How Mothballs Actually Work
Mothballs kill insects through a process called sublimation, where the solid chemical converts directly into a gas without melting into a liquid first. This is the same process that makes dry ice “smoke.” As the mothball shrinks over weeks or months, it fills the surrounding air with toxic vapors.
Here’s the critical detail most people miss: mothballs only work in an airtight container. The gas needs to build up to a concentration high enough to kill moths and their larvae. Tossing a few mothballs into an open closet or dresser drawer won’t reach lethal levels for insects. It will, however, expose you to a steady stream of pesticide fumes for no benefit. Proper use means placing mothballs with your stored clothing inside a sealed garment bag, trunk, or storage bin, then keeping that container closed.
Health Risks of Exposure
Both mothball chemicals pose real dangers, especially with prolonged or direct exposure. Naphthalene is the more hazardous of the two. It destroys and alters red blood cells so they can no longer carry oxygen efficiently, which can lead to organ damage. Some people carry a genetic condition (affecting roughly 400 million people worldwide) that makes them significantly more vulnerable to naphthalene’s effects on red blood cells.
Short-term symptoms of naphthalene exposure include nausea, vomiting, abdominal pain, and headaches. Stomach problems may not appear until two days after contact. With larger exposures, more serious symptoms can develop: confusion, seizures, jaundice (yellowing of the skin), blood in the urine, shortness of breath, and rapid heart rate. In severe cases, naphthalene can also create an abnormal form of hemoglobin that doesn’t carry oxygen, starving the heart, brain, and other organs.
Paradichlorobenzene is less acutely dangerous. Small, accidental exposures typically cause only mild irritation, nausea, or headaches. But large ingestions or chronic exposure over time can cause impaired balance, muscle weakness, behavioral changes, and the same type of red blood cell destruction seen with naphthalene.
Risks to Children and Pets
Mothballs look like candy or toys to young children and smell interesting enough for pets to investigate. Swallowing even one naphthalene mothball can cause serious poisoning in a small child or animal, including seizures, kidney damage, and coma. If you suspect a child has swallowed a mothball, give them a small amount of water and contact Poison Control immediately at 1-800-222-1222. Because naphthalene and paradichlorobenzene require different levels of concern, identifying which type was swallowed helps determine the right response.
Why Outdoor Use Is Illegal
Mothballs are EPA-regulated pesticides, and their labels specify exactly where and how they can legally be used. Using them in any way the label doesn’t describe is a violation of federal law. One of the most common misuses is scattering mothballs in gardens, crawl spaces, attics, or yards to repel snakes, squirrels, mice, or other wildlife. This doesn’t work (the vapors disperse too quickly outdoors to reach effective concentrations), and it contaminates soil, plants, and water while creating poisoning risks for children, pets, and wildlife.
Safer Alternatives
Several natural options can repel moths without the toxicity of naphthalene or paradichlorobenzene. Dried lavender is one of the most effective, thanks to compounds like camphor and a natural chemical called cineole that moths avoid. Cedar blocks and cedar oil work on a similar principle, and rosemary contains some of the same repellent compounds as lavender, though with somewhat lower effectiveness. Pheromone traps, which use synthetic moth scents to lure and catch adult males, can help monitor and reduce infestations without any chemical exposure at all.
None of these alternatives kill moth larvae the way mothballs do, so they work best as preventive measures. The most reliable non-chemical protection is simply washing or dry-cleaning clothes before storing them (moth larvae feed on sweat, skin oils, and food stains, not clean fabric) and sealing them in airtight bags or bins.
Getting Rid of Mothball Smell
The lingering odor of mothballs is the chemical itself, still off-gassing from fabric and surfaces. Removing it takes patience and a layered approach.
Start by airing out contaminated clothing outdoors for at least a full day. Sunlight and fresh air break down the residual chemicals and reduce the smell noticeably. For clothes that still have an odor after airing out, run them through a wash cycle with a half cup of white vinegar in place of detergent, then follow up with a regular wash using your normal soap.
For rooms or storage spaces, open windows and run fans to increase ventilation. Wipe down hard surfaces and storage containers with a 50/50 mixture of water and vinegar. Place bowls of white vinegar or activated charcoal around the room to absorb lingering fumes, replacing them every few days. Coffee grounds work as an alternative absorbent. If you can’t open windows, a HEPA air purifier will help capture odor-causing molecules. For stubborn cases that resist everything else, an ozone generator can destroy the remaining odor molecules through oxidation, though you’ll need to vacate the room while it runs.