They don't work
The mothball myth is one of the most persistent in wildlife control: scatter mothballs and raccoons, snakes, or armadillos will leave. They won't. Study after study and decades of field experience show the same thing — animals walk right past mothballs, and sometimes nest next to them. The smell dissipates outdoors within days, and wildlife habituates to it even faster.
They're illegal to use this way
Here's the part most people don't know: mothballs are registered pesticides, and the label specifies indoor use in sealed containers for moths. Using them outdoors, in attics, or under sheds to repel wildlife is off-label use — a violation of pesticide law. It sounds absurd for something sold at every grocery store, but the regulation is real and the fines are real.
They're genuinely hazardous
Mothballs contain naphthalene or paradichlorobenzene — chemicals that are toxic to kids, pets, and wildlife, and that contaminate soil and water. Dogs eat them. Cats are poisoned by them. They've caused documented pet deaths. Scattering poison around your yard to deter an animal that isn't deterred by it is all downside, no upside.
What actually works instead
The unglamorous truth: exclusion and habitat work. Seal the entry. Cap the chimney. Screen the vents. Remove the food. Trim the branches. There is no sprinkle, spray, or gadget that substitutes for closing the gap the animal walks through. Every "repellent" product — mothballs, ammonia, predator urine, ultrasonic stakes — fails the same way: the animal's need for food or shelter outweighs a bad smell. Read about real exclusion work.