Several common reasons for dog hair loss:

1. It may be that the dog is shedding. During the shedding season, the dog will shed some old hair and then replace it. New hair.

2. Dogs eat allergic foods that cause skin diseases and hair loss.

3. If the dog has parasites that cause skin diseases, it will also cause hair loss.

4. If the owner bathes the dog too frequently, it will cause the pH imbalance of the dog's skin and aggravate the hair loss.

5. If the owner gives the dog too much salt for a long time, it will also cause the dog to lose hair.