Generally, most dogs need a bath once a week or once every two weeks. If they get into something outside and they smell, they may require a bath more often. Check to see how your dog is acting after a bath to see whether you are bathing them too frequently. If they are scratching and itchy, the dog shampoo you are using may have stripped their skin of natural oils. A dog's skin may become dry or flaky. Oils are important for a dog because they help the animal maintain a healthy coat. If dryness occurs, spread out their baths, putting more time in between each one. Be sure to brush your dog every week. This can keep his fur from tangling and help keep him clean.