✔ 最佳答案
Fleas can cause anemia, tape worms, among other things as well. If left untreated then yes they will get sick and die. Depending on where you live and how the cold the weather is, freezing weather can kill the fleas outside, however, not inside the house or on your pet. IMO you should not wait until it gets cold outside before the dog gets treated. You must treat the yard, the house and the pet in order to get the flea population under control. Treating just one will not get rid of them.