The American College of Veterinary Dermatology has said that there is no commonly accepted standard of bathing frequency. This is because there are so many factors to consider when determining how often a pet with normal skin should be bathed. The lifestyle of the dog can affect the frequency, as dogs used for hunting or those who spend more time outdoors require more frequent baths than those who spend most of their time indoors. Additionally, dogs with thick coats tend to accumulate oil and debris, requiring frequent baths.
For a healthy dog that has no skin irritation, bathing as needed is most appropriate. For dogs that have skin issues, or allergies it is best to speak to your veterinarian to determine the cadence at which to bathe your dog. They will also be able to advise on specific shampoos that will help their conditions. Lastly, always read the product label of the shampoo you are using prior to use, thoroughly to ensure it’s being used appropriately and according to the instructions.