What is in moth balls? Is it harmful to people?

Clothes moths can be a real problem in clothes made from natural fibers (especially wool). To combat these pests, mothballs are small, solid chemical products used to repel clothes moths and protect clothing from damage.

There are two different types of moth balls used to ward off moths. In one type, the main ingredient is naphthalene, and in the other it is paradichlorobenzene. The idea with both chemicals is to deter moths and kill moth larvae with toxic fumes. Both naphthalene and paradichlorobenzene sublimate, meaning they transition from a solid straight to a gas. The gas is toxic to the clothes moths and other fabric-eating insects.

For either of these chemicals to be effective, they need to be placed with the clothing in an airtight container (like a garment bag) so the fumes can build up and kill the moths. In a sealed atmosphere like this, the mothball fumes are not harmful to people because they are contained.

Designed to be used in enclosed spaces like closets or storage containers, mothballs are a traditional method for preserving garments, especially those made of natural fibers prone to insect damage. However, due to their chemical composition, there are health and safety considerations that come with their use.

The main threat would occur when opening the containers, or from wearing clothes immediately after opening it. This scenario can be especially problematic for small children, who aren't aware of the toxic substances. A solution is to open the containers outside and let the clothes hang and air out for a day before wearing.

Naphthalene mothballs pose several health risks, especially when used improperly or in poorly ventilated areas. Here are some of the key health concerns:

Toxicity: Both naphthalene and paradichlorobenzene can be toxic. Inhaling the fumes over a prolonged period can lead to health issues.

Respiratory problems: The strong toxic fumes from mothballs can irritate the respiratory tract, potentially causing difficulty breathing, coughing, or more serious respiratory issues, especially in individuals with pre-existing conditions like asthma.

Neurological effects: High concentrations of chemical exposure can lead to neurological symptoms such as headache, dizziness, or in severe cases, confusion and seizures.

Skin and eye irritation: Direct contact with mothballs can cause skin and eye irritation. The chemicals can be harsh and may lead to rashes or chemical burns on sensitive skin.

Carcinogenic risks: Naphthalene has been identified as a possible human carcinogen by some health agencies, indicating a potential risk of cancer from long-term exposure.

Hemolytic anemia risk: In some individuals, particularly infants and those with a genetic condition called G6PD deficiency, naphthalene can cause a type of anemia called acute hemolytic anemia, where red blood cells are destroyed faster than they can be made.

Environmental impact: Besides personal health risks, the chemicals in mothballs can also be harmful to the environment, contributing to air and soil pollution.

The U.S. Environmental Protection Agency (EPA) categorizes mothballs (and moth flakes, for that matter) as pesticides. They emphasize strict compliance with safety instructions printed on the pesticide label of any mothball products sold in the United States.

These regulations are in place due to the potential risks of the active ingredients found in mothballs. They're also imposed to prevent mothball products from being used for purposes not described on the label, such as wildlife repellents. The label language makes clear that mothball fumes are intended to kill moths — that's it!

We all seem to have an aunt whose entire house smells like moth balls, and we have all walked in to public restrooms where the smell of paradichlorobenzene is nearly overpowering. Are these diluted fumes healthy? The answer is "probably not." So, how can you outfox a clothes moth without slowly poisoning yourself?

A less toxic alternative is cedar blocks, shavings, or oil. The blocks are expensive, but cedar shavings in the form of hamster bedding can be very inexpensive. Deodorant blocks are another safe alternative. Again, the container or garment bag needs to be sealed for long periods in order for the cedar scent to have a real effect on moths.

­This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.