Mothballs will kill fleas, but extreme care should be taken in handling, using and storing them. Mothballs release benzene fumes, which can cause respiratory illness and even cancer.
Mothballs were once made of naphthalene, but it was found to be flammable and unsafe. Mothballs are now made from para-dichlorobenzene, a chemical that, like naphthalene, sublimates, meaning it releases a gas directly from its solid state without liquefying first.
Mothballs are small, round, crystalline lumps of pesticide that gradually release toxic fumes that will kill moths and moth eggs when sealed with clothing in airtight containers such as storage closets and garment bags. These fumes will be released wherever mothballs are placed, and they can harm or injure people and pets as well as insects.
Fleas usually are present in carpets and on upholstered furniture, but it is very dangerous to leave mothballs in these areas. The fumes alone can be harmful, and because mothballs are crystalline lumps, they can be mistaken for hard candy by children or eaten by pets. Ingesting mothballs can cause extreme sickness and even death. Benzene can also damage the soil, so homeowners should not leave mothballs outside as mouse or snake repellents.
Use for Flea Killing
The most common way to use mothballs against fleas is to drop one in the vacuum cleaner bag, where it will kill any fleas or flea eggs when you vacuum. The used vacuum cleaner bag should be taken out of the house and disposed of afterward because of the danger from benzene fumes and also because flea eggs will continue to hatch and escape from the bag.
Use gloves to avoid direct contact with mothballs. Benzene can irritate the eyes and nose and cause severe headaches, nausea, vomiting and diarrhoea. Prolonged or repeated exposure can cause liver and kidney disease. Store mothballs in a tightly sealed container well out of reach of children and pets. The fumes from mothballs can cause respiratory problems, and the U.S. Department of Health and Human Services identifies benzene as a carcinogen.