If your dog doesn’t have any skin disease, once a week is fine. Bathing your dog more than once a week can cause dry skin and may even pave a way for a skin disease to develop. However, if your dog has a skin disease, bathe it twice a week using a soap or a shampoo that can help treat its condition. Note that, a product that works with someone else’s dog may or may not work with your dog so be attentive to how its soap or shampoo affects its skin and fur. Change it when you see anything that’s not good. You may also try organic or herbal products.