Mothballs can be toxic to cats. Mothballs are generally used to repel moths that destroy clothing. Mothballs contain naphthalene or paradichlorobenzene. These ingredients can be formulated into cakes, balls, or flakes. As little as one mothball can potentially result in significant illness in an average-sized cat.
Depending on the amount ingested signs of toxicity include: lethargy, weakness, vomiting, diarrhea, abdominal pain, lack of appetite, seizures and/or coma.
Keep mothballs or moth prevention products stored away from your kitty.
For more information mothball ingestion, please read Moth Repellent Product Poisonings