Camphor balls are harmful to cats, mainly because they contain substances such as naphthalene and paradichlorobenzene. When cats come into contact with or ingest them, they may experience vomiting, diarrhea, convulsions, and damage to their red blood cells, leading to anemia and liver dysfunction.

In addition, small items that are harmful to cats include:
1. Plastic bags. Because of their playful nature, even a plastic bag can keep a cat entertained for half a day. If a cat accidentally gets tangled in a plastic bag or is sealed inside one, it is very dangerous and could suffocate.
2. Deep-mouthed containers. If the owner is not around and the cat gets stuck inside while playing, it may suffocate and die.
3. Hair ties. Hair ties are small items and can easily be swallowed, potentially leading to intestinal obstruction. Therefore, hair ties should be stored properly and not left lying around.
4. Fishing line and hooks. Fishing line and hooks have a fishy smell, which cats find very interesting. If a cat accidentally swallows them, it could injure its mouth or even its stomach.
5. Toilet cleaner. Cats generally like to drink toilet water, even though they think it's clean. However, water that has just been used with toilet cleaner is somewhat toxic and can affect a cat's health.