People use mothballs to kill clothes moths and carpet beetles, the two main insect species that destroy wool, silk, fur, and other natural fibers stored in closets and drawers. Mothballs are classified as insecticides, not repellents. They work by releasing toxic fumes inside sealed containers, killing insects at every life stage from egg to adult. Despite their long history as a household staple, mothballs are widely misused, and many people don’t realize they’re handling a registered pesticide with strict legal requirements for how and where it can be applied.
How Mothballs Actually Work
Mothballs are made from one of two chemicals: naphthalene or paradichlorobenzene, both present in very high concentrations. These chemicals have a useful physical property. Instead of melting into a liquid, they sublimate, meaning they transition directly from a solid into a gas at room temperature. Molecules on the surface of the mothball gradually gain enough energy to break free and become airborne vapor. This process continues slowly until the mothball disappears entirely.
When mothballs are placed inside a tightly sealed container, those vapors build up to a concentration high enough to kill clothes moths and carpet beetles. The gas is toxic to the insects’ respiratory systems, and at sufficient levels it destroys eggs, larvae, pupae, and adults alike. This is a critical detail most people miss: mothballs only work in airtight spaces where the fumes can accumulate. Tossing a few into an open closet or dresser drawer won’t reach the concentration needed to kill anything. It will, however, fill your living space with toxic fumes.
What They’re Designed to Protect Against
The real threat to your stored clothing isn’t adult moths flying around your house. It’s the larvae. Both clothes moths and carpet beetles go through egg, larva, pupa, and adult stages, and the larval stage is when the damage happens. Larvae feed on keratin, the protein found in animal-based fibers like wool, cashmere, silk, and fur. A single unnoticed infestation can chew through expensive sweaters, rugs, and upholstery before you spot any adult moths.
Mothballs were developed as a way to protect clothing in long-term storage, particularly seasonal items packed away in trunks, garment bags, or storage bins for months at a time. The sealed environment these items sit in is exactly what mothballs need to be effective.
Why Misuse Is So Common
Despite their familiar presence in homes, mothballs are one of the most commonly misused pesticide products in the United States. The EPA has flagged illegal versions of naphthalene mothball products as a particular hazard to young children. The product label specifies exactly where and how mothballs can legally be used, and using them in any way not described on the label is illegal.
People routinely scatter mothballs in attics, crawl spaces, gardens, and yards to repel snakes, mice, squirrels, raccoons, and other wildlife. None of these are approved uses. Mothballs are registered to kill fabric pests inside sealed containers, period. Using them outdoors exposes children, pets, and wildlife to toxic chemicals and contaminates soil and groundwater. The familiar smell might seem harmless, but that odor is the pesticide itself becoming airborne in a space where it was never meant to be.
Health Risks of Exposure
The reason proper use matters so much is that both naphthalene and paradichlorobenzene are genuinely dangerous to humans, especially with prolonged or repeated exposure. Naphthalene is the more hazardous of the two. Breathing in the fumes or accidentally ingesting even a small amount can cause headaches, nausea, vomiting, diarrhea, abdominal pain, and fever.
More serious naphthalene poisoning triggers a condition where red blood cells break apart in the bloodstream. This leads to anemia, dark brown urine, jaundice, and in severe cases, kidney and liver damage. Children are at higher risk because they may mistake mothballs for candy, and their smaller bodies are more vulnerable to the toxic effects. Even low-level, long-term inhalation from mothballs used in unsealed spaces can accumulate health consequences over time. One common scenario: someone places mothballs throughout an open closet or under a bed, and the fumes slowly permeate a bedroom for months.
How to Use Them Correctly
If you do choose to use mothballs, the rules are straightforward. Place them inside a container that seals completely, like a plastic storage bin with a locking lid, a vacuum-sealed garment bag, or a trunk with a tight closure. The clothing should be clean before storage, since body oils and food stains attract pests. Follow the label for how many mothballs to use per volume of space. More is not better; it just increases your chemical exposure when you open the container.
Keep the sealed container in a space where people and pets won’t breathe the fumes if any escape. When you eventually open the container, do it outdoors or in a well-ventilated area and let the clothing air out thoroughly before wearing it. The distinctive mothball smell clings to fabrics and can take real effort to remove. Ventilation is the first step: hanging clothes outside in fresh air for several hours. For stubborn odors, cedar sachets and activated charcoal placed near the clothing can absorb lingering traces. Washing or dry cleaning the items usually finishes the job.
Alternatives That Skip the Toxicity
Given the health risks and strict usage requirements, many people have moved away from mothballs entirely. The most popular natural alternatives are cedar and lavender, both of which repel moths but don’t kill them. Cedar wood contains oils that deter clothes moths from settling in a space. The catch is that cedar’s effectiveness fades quickly, and you’ll need to replace cedar blocks, hangers, or balls every two to three months as the oils dissipate. Lavender works the same way and has the same limitation: it loses potency over time and won’t stop an active infestation.
For people dealing with an existing moth problem, pheromone traps are a more targeted option. These use synthetic versions of the scent female moths produce to attract males, luring them onto a sticky surface. This interrupts the breeding cycle by catching adult males before they can mate. Pheromone traps are non-toxic, odor-free, and effective at reducing moth populations over time. They won’t kill larvae already feeding on your clothes, but they prevent the next generation from being laid.
The most effective prevention strategy combines several approaches: storing clean clothes in sealed containers or bags, using cedar or lavender as a first-line deterrent, setting up pheromone traps to catch any adults in the area, and regularly inspecting stored items for signs of damage. For valuable items like heirloom wool blankets or fur coats, professional cold storage eliminates the risk entirely, since clothes moths can’t survive freezing temperatures.