Causes of redness at the corners of a dog's mouth:

1. It may just be red hair. If the hair around the mouth is not cleaned in time, it will cause the hair to be oxidized and turn red, so you need to eat and drink. After that, you should clean the dog’s mouth hair in time.

2. It is also possible that the dog is accidentally injured while playing with other dogs, which may cause the skin to become red. The owner can disinfect the wound, but try not to let the dog lick it.

3. In addition to skin abnormalities, it may also be caused by skin diseases, allergies, eczema, etc. At this time, the dog should be taken to the hospital for examination to determine the cause and formulate a corresponding treatment plan.