We shouldn't bathe a dog more than one time per month. If we bathe them over that period of time, it's even better. We need to know that dogs possess some properties in their skin and their "hair" is different than ours. It is their "coat" during winter and their summer protection.
If we bathe it too frequently, we weaken those qualities. Its layer of fat acid is weakened becoming apparent in a loss of shine and hair quality, as well as an increase in the probability of allergic processes. Soon, a characteristic odour appears due to constant bathing; it resembles that smell of a dirty dog. If we wait for a couple of days, that smell will disappear, though. There are some fat acid tablets which might help improve the skin and fur of our dog. On the other hand, we might be bathing our dog more often than usual due to a pathology we are trying to fight.
If due to the habits of our dog we need to increase how often we bathe our dog, I recommend you use a shampoo which is specific for that task and less harmful. You can get such product at specialized shops.