Mothballs are specifically designed and registered to repel and kill one type of pest: clothes moths. Despite widespread belief that they work against mice, snakes, squirrels, and other wildlife, mothballs are only labeled for use against fabric-eating insects, primarily the common clothes moth (and to some extent, carpet beetles). Using them for anything else is both ineffective and potentially illegal.
What Mothballs Actually Target
The name says it all. Mothballs exist to protect stored clothing and fabrics from clothes moths, the most common culprit behind holes in sweaters, wool coats, and other natural-fiber garments. These moths lay eggs on fabric, and the larvae feed on wool, silk, fur, and feathers, sometimes for months before you notice the damage.
Mothballs work by releasing a toxic vapor that builds up inside an enclosed space, like a sealed garment bag, storage bin, or trunk. The concentration of gas needs to reach a level high enough to actually kill the moths and their larvae. This is why the product label specifies use in airtight containers. Left out in the open, the vapor dissipates too quickly to reach lethal concentrations for any pest.
Why They Don’t Work on Mice, Snakes, or Squirrels
One of the most persistent pest-control myths is that scattering mothballs around your yard, attic, or crawl space will drive away rodents, snakes, bats, or other unwanted animals. The reality is much less impressive. The amount of active chemical in a single mothball is far too small to deter a rat or mouse, and the odor fades rapidly in open air. Snakes are not repelled by mothballs either. Studies and pest-control professionals consistently confirm this.
Beyond being ineffective, using mothballs outdoors or in open indoor spaces to repel wildlife is an off-label use, which violates federal pesticide law. The EPA registers mothballs strictly for fabric pest control in enclosed containers. Scattering them in gardens, under porches, or in attics exposes children, pets, and wildlife to a toxic pesticide with no real benefit. Outdoor use also risks contaminating soil and groundwater.
How Mothballs Work Chemically
Most mothballs contain one of two active chemicals: naphthalene or paradichlorobenzene. Both are solid at room temperature but slowly turn into a gas, a process called sublimation. That distinctive, sharp smell you associate with mothballs? That’s the pesticide itself entering the air. When you smell mothballs, you are literally inhaling the active ingredient.
Inside a sealed container, these vapors accumulate until they reach a concentration toxic enough to kill moth eggs, larvae, and adult moths. In an open room, the gas never builds up enough to harm insects, let alone larger animals like mice or snakes. This is the fundamental reason mothballs fail as a general-purpose repellent.
Health Risks of Mothball Exposure
Mothball fumes are not just unpleasant. They pose real health risks, especially with prolonged or repeated exposure. Breathing in naphthalene vapors can cause headaches, nausea, dizziness, and vomiting. At higher levels of exposure, naphthalene breaks down red blood cells, leading to a condition called hemolytic anemia where the blood can no longer carry oxygen properly. Kidney and liver damage can also occur.
Certain people face even greater risk. Individuals with an inherited enzyme deficiency (relatively common in people of African, Mediterranean, and Southeast Asian descent) are significantly more vulnerable to naphthalene-induced anemia. Infants have developed anemia simply from wearing clothes or using blankets that were stored with mothballs and not washed afterward. Pregnant women who inhaled mothball vapors or ingested mothballs gave birth to babies with hemolytic anemia.
Both the World Health Organization and the U.S. EPA classify naphthalene as a possible human carcinogen based on animal studies. Pets are also at risk, particularly cats and dogs that might chew on or swallow a mothball.
Safer Ways to Protect Your Clothes
If your goal is keeping clothes moths and carpet beetles away from stored garments, several alternatives work well without the toxic tradeoffs.
- Thorough cleaning before storage. Moths and beetles are attracted to body oils, food stains, and sweat on fabric. Washing or dry cleaning clothing before packing it away removes the food source larvae need.
- Regular vacuuming. Frequent, thorough vacuuming of carpets, closet floors, shelves, and upholstered furniture removes eggs and larvae before they can cause damage. Pay extra attention to pet hair, which is a food source for moth and beetle larvae.
- Airtight storage. Sealed plastic bins or vacuum-sealed bags physically block moths from reaching your clothes. No chemicals needed.
- Cedar. Cedar-lined closets and cedar chests release volatile oils that help deter fabric pests, though the oils lose potency after several years and the wood may need to be lightly sanded to refresh it.
- Freezing. For items you suspect are already infested, storing them at 0°F for 48 to 72 hours kills moths, beetles, and their larvae at all life stages.
Regular inspection of stored heirloom items, wool rugs, and seasonal clothing catches problems early. A combination of clean storage, airtight containers, and routine checks is more effective and far safer than relying on mothballs scattered around a closet.