You should bathe your dog as often as once or twice a month if the dog doesn't get too dirty.
However if your dog gets dirty then you should bathe them as needed.
But bathing your dog too much can dry out their skin and damage their fur coat.
The bathing frequency of your dog also depends on the dog breed and coat type.
For dogs that have oily coats such as Golden Retriever dogs they may require a bath every couple of weeks.
Dogs that have thick fur coats such as Chow Chows and Siberian Huskies will shed often and regularly and don't require as many baths.
Hairless dog breeds like Xoloitzcuintli and Chinese Crested dogs require baths weekly.
Some dogs may only need a bath once ever month to every 3 months.
The signs that your dog needs a bath are.
The dog has a strong and unpleasant odor.
The dog has been in dirt or mud.
The dog has debris or dirt in their fur coat.
The dog has excessive shedding or matting.
The dog has skin irritation or licking themselves more than they usually do.
If you never do bathe your dog then the dog can be exposed to skin sores, infections, parasites and more.
Bacteria, feces, fungi and dead skin cells can live in the dogs fur.