Dogs with itchy tails and biting themselves may be caused by parasites, skin diseases, lack of trace elements or anal diseases. You need to check whether there are parasites and skin diseases on your dog. If you need to bathe your dog and deworm it on time, you should also supplement your dog with trace elements appropriately. If your dog’s anus is red and swollen, it’s best to take your dog to a pet hospital for examination and treatment to avoid worsening of the condition.