Mothballs are not safe to use in open living spaces. They are nearly 100% pesticide, and when you smell that distinctive mothball odor, you are inhaling insecticide vapor. Mothball labels specifically direct users to place them only in tightly sealed containers, like garment bags or storage bins with airtight lids, to prevent fumes from accumulating in rooms where people and pets breathe. Using them any other way is both a health risk and, in the United States, technically illegal.
What Mothballs Actually Are
Mothballs aren’t a mild household product. They are registered pesticides made of either naphthalene or paradichlorobenzene, with virtually no inactive ingredients. Both chemicals slowly transition from a solid directly into a gas, a process called sublimation. That gas is what kills clothes moths and their larvae. But it doesn’t distinguish between insects and the humans or animals breathing the same air.
The International Agency for Research on Cancer classifies both naphthalene and paradichlorobenzene as Group 2B, meaning they are possibly carcinogenic to humans. The European Union has gone further: naphthalene mothballs are banned outright under EU chemical safety regulations, where naphthalene is classified as a carcinogenic substance. Products containing it are pulled from shelves when discovered.
Health Effects of Breathing Mothball Fumes
Short-term exposure to mothball vapor can cause headaches, nausea, dizziness, and irritation of the eyes, nose, and throat. These symptoms often appear when mothballs are placed in closets, dresser drawers, or rooms without airtight containment, allowing fumes to build up in your living space. The stronger the smell, the higher the concentration you’re breathing.
Longer or repeated exposure raises more serious concerns. Naphthalene can damage red blood cells, leading to a condition called hemolytic anemia where the body destroys its own blood cells faster than it can replace them. This risk is especially pronounced in infants and people with a genetic enzyme deficiency called G6PD, though case reports have documented severe reactions even in infants without that deficiency. In one published case, a child who ingested a mothball developed hemolytic anemia and sustained brain damage from oxygen deprivation.
A single mothball can cause serious harm if eaten by a small child. Because mothballs look like candy or toys, accidental ingestion is a real and documented danger in households with young children.
Risks to Dogs and Cats
Pets are highly vulnerable to mothball poisoning, whether from chewing on one, inhaling concentrated fumes, or simply lying near an open container. Naphthalene is more toxic than paradichlorobenzene in animals. Early signs of naphthalene exposure in pets include vomiting and loss of appetite, which can progress to anemia, difficulty breathing, pale gums, tremors, and seizures with larger exposures.
Paradichlorobenzene poisoning in pets looks slightly different: abdominal pain, vomiting, lethargy, and trembling. Chronic or repeated exposure can cause liver and kidney damage and eventually anemia. Because cats and dogs explore with their mouths and noses, even a mothball that rolled under furniture poses a serious risk.
The Legal Rules You Might Not Know
In the U.S., mothballs are regulated as pesticides by the EPA. Their labels carry specific legal instructions: use them only inside tightly sealed containers where fumes cannot escape into living areas. Placing mothballs in an open closet, scattering them in a basement, tucking them into dresser drawers, or spreading them in a garden are all violations of federal pesticide law.
One of the most common mistakes is using mothballs in containers that aren’t airtight. A cardboard box, a loosely closed bin, or an unsealed garment bag all allow toxic vapors to leak into the surrounding room. Another widespread misuse is placing them outdoors to repel snakes, rodents, or other wildlife. This is both illegal and ineffective, and it contaminates soil and water while putting children and animals at risk.
If You Already Have Mothballs in Your Home
If mothballs are sitting in open areas of your home, remove them. Ventilate the space by opening windows and running fans to push contaminated air outside. The smell can linger for weeks or even months because naphthalene and paradichlorobenzene absorb into fabrics, wood, carpet, and drywall. Washing affected clothing and textiles, wiping down hard surfaces, and continuing to air out the space will gradually reduce the concentration.
Don’t throw old mothballs in the regular trash. They are classified as household hazardous waste. Many counties and municipalities run collection programs, either through annual events, permanent drop-off facilities, or curbside pickup services. Check with your local waste management agency for accepted items and scheduling. Some programs charge a small fee and require proof of residency.
Alternatives That Actually Work
If you’re trying to protect stored clothing from moths, the safest approach is also the most effective: clean everything before storing it (moths are attracted to body oils and food residue on fabric), then seal garments in airtight bags or containers. Moths can’t get in, and you don’t need any chemical at all.
Natural repellents like cedar and lavender work by releasing plant-based compounds that discourage moths from settling and laying eggs. They’re genuinely safer for your household, but they come with a significant limitation. Cedar blocks and lavender sachets lose their potency in one to three weeks and need regular refreshing. Chemical mothballs, by contrast, release vapor continuously for two to twelve months in a sealed space. For long-term storage where you won’t be checking in frequently, airtight containers alone are your best bet, possibly combined with cedar that you refresh seasonally.
Permethrin-treated storage products offer a middle ground. They provide months of residual protection without filling your air with toxic vapor, since the chemical stays on the treated surface rather than sublimating into gas. These are available as sprays for fabric or as pre-treated storage bags.
The Bottom Line on Indoor Use
Mothballs are safe only when used exactly as the label directs: inside a sealed, airtight container, away from living spaces, out of reach of children and pets. In practice, very few people use them this way. If you can smell mothballs anywhere in your home, the concentration in your air is already higher than it should be, and you’re breathing in pesticide with every breath. For most households, sealed storage containers with or without natural repellents provide effective moth protection without the toxic tradeoff.