Mothballs are small balls of chemical pesticide and deodorant, sometimes used when storing clothing and other articles susceptible to damage from mold or moth larvae (especially clothes moths like Tineola bisselliella). Use of mothballs when clothing is stored out of season has given rise to the colloquial usage of the terms "mothballed" and "put into mothballs", to refer to anything which is put into storage or whose operation is suspended.


Older mothballs consisted primarily of naphthalene, but due to naphthalene's flammability, many modern mothball formulations instead use 1,4-dichlorobenzene. The latter formulation may be somewhat less flammable, although both chemicals have the same NFPA 704 rating for flammability. The latter chemical is also variously labeled as para-dichlorobenzene, p-dichlorobenzene, pDCB, or PDB, making it harder to identify unless all these synonyms are known to a potential purchaser. Both of these formulations have the strong, pungent, sickly-sweet odor often associated with mothballs. Both naphthalene and 1,4-dichlorobenzene undergo sublimation, meaning that they evaporate from a solid state directly into a gas; this gas is toxic to moths and moth larvae.

Naphthalene and 1,4-dichlorobenzene should not be used together because the mixture may cause damage to items being preserved.[1]

Due to the health risks of 1,4-dichlorobenzene, and flammability of naphthalene, other substances like camphor are sometimes used.


In addition to repelling or killing insects such as moths and silverfish, mothballs can be used as a repellent to keep bats from establishing themselves in attics. Mothballs may repel snakes or mice. Mothballs have the potential to be a hazard to pets, livestock or children that may come into contact with them. However, mothball labels instruct proper use in a sealed container.[2] Older-formula mothballs have also been used by drag racers to enhance the octane rating of fuel, by dissolving the mothballs in some of the fuel and filtering out the remains with a filter paper.


Some have claimed mothballs are ineffective as snake repellents[3] or as rodent repellents.[4] Mothballs, however, continue to be advertised as a squirrel repellent and are an ingredient in some commercial vermin and snake repellent products. Some websites claim they are ineffective as a deterrent to prevent squirrels from nesting in building interiors.[5][6]

In the 2004 MythBusters episode "Scuba Diver, Car Capers", it is shown to be "plausible" that adding mothballs to a car's fuel tank would increase its horsepower.

Health risks

The US Department of Health and Human Services (DHHS) has determined that 1,4-dichlorobenzene "may reasonably be anticipated to be a carcinogen". This has been indicated by animal studies, although a full-scale human study has not been done.[7] The National Toxicology Program (NTP), the International Agency for Research on Cancer (IARC) and the state of California consider 1,4-dichlorobenzene a carcinogen.[8]

Exposure to naphthalene mothballs can cause acute hemolysis (anemia) in people with glucose-6-phosphate dehydrogenase deficiency.[9] IARC classifies naphthalene as possibly carcinogenic to humans and other animals (see also Group 2B).[10] IARC points out that acute exposure causes cataracts in humans, rats, rabbits, and mice. Chronic exposure to naphthalene vapors is reported to also cause cataracts and retinal hemorrhage.[11] Under California's Proposition 65, naphthalene is listed as "known to the State to cause cancer".[12] However, the Proposition 65 list of harmful chemicals includes many popular foods and prescription and over-the-counter medications, including coffee, aloe vera extract, all alcoholic beverages, aspirin and other substances not included on most other state and federal regulatory agencies' lists of dangerous chemicals.

Research at the University of Colorado at Boulder revealed a probable mechanism for the carcinogenic effects of mothballs and some types of air fresheners.[13][14]

1,4-Dichlorobenzene is a neurotoxin. It has been abused as an inhalant, causing a variety of neurotoxic effects.[15][16]

Mothballs containing naphthalene have been banned within the EU since 2008.[17][18]


As discussed in more detail at Tineola bisselliella, alternatives to mothballs to control clothes moths include dry cleaning, freezing, thorough vacuuming, or washing in hot water.[19] Camphor is also used as a moth repellent, particularly in China.[20] Unlike naphthalene and dichlorobenzene, camphor has medicinal applications and is not regarded as a carcinogen, though it is toxic in large doses.

Pheromone traps are also an effective tool used when attempting to protect valuable clothing.

See also


  1. "Collecting and Preserving Insects and Mites: Tools and Techniques". United States Department of Agriculture - Agricultural Research Service. Retrieved June 26, 2011.
  2. Uncommon Uses for Common Household Products. Frank W. Cawood and Associates. 2000. p. 126. ISBN 1-890957-39-9.
  3. "Snakes In and Around the House". N?IC. National Pesticide Information Center. Retrieved February 21, 2016.
  4. "Problem Wildlife in the Garden and Yard". N?IC. National Pesticide Information Center. Retrieved February 21, 2016.
  5. "Guide to Safe Removal". Squirrels in the Attic. Retrieved April 19, 2012.
  6. "Problem Wildlife in the House". N?IC. National Pesticide Information Center. Retrieved May 24, 2013.
  7. "ToxFAQs™ for Dichlorobenzenes". Toxic Substances Portal. Agency for Toxic Substances and Disease Registry. Retrieved May 24, 2013.
  8. "p-dichlorobenzene (1,4-dichlorobenzene)" (PDF). Material Safety Data Sheet. Archived from the original (PDF) on May 22, 2013. Retrieved May 24, 2013.
  9. Santucci, K; Shah, B. (January 2000). "Association of naphthalene with acute hemolytic anemia". Academic Emergency Medicine. 7(1):42-7.
  10. "Some Traditional Herbal Medicines, Some Mycotoxins, Naphthalene and Styrene". IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. 82: 367. 2002. Retrieved December 25, 2008.
  11. "Naphthalene". Air Toxics Web Site. US Environmental Protection Agency. Retrieved May 24, 2013.
  12. Proposition 65, Office of Environmental Health Hazard Assessment
  13. "Scientists May Have Solved Mystery Of Carcinogenic Mothballs". June 20, 2006.
  14. "Mothballs, air fresheners and cancer". Environmental Health Association of Nova Scotia. Retrieved May 24, 2013.
  15. "Mothball sniffing warning issued". BBC News. July 27, 2006.
  16. "Twin Girls with Neurocutaneous Symptoms Caused by Mothball Intoxication". The New England Journal of Medicine. July 27, 2006.
  17. Gray, Kerrina (November 17, 2013). "Council warned against use of poisonous moth balls". Your Local Guardian. Newsquest (London) Ltd. Retrieved November 23, 2012.
  18. Alderson, Andrew (November 15, 2008). "Holy straight bananas – now the Eurocrats are banning moth balls". The Telegraph. Retrieved November 23, 2013.
  19. Eisenberg, Sheryl. "Mothballed". This Green Life. Natural Resources Defense Council. Retrieved May 24, 2013.
  20. 国务院经贸办、卫生部关于停止生产和销售萘丸提倡使用樟脑制品的通知(国经贸调(1993)64号)
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