Regular bathing removes dander, loose hair, skin oils, and debris that can accumulate in pores. It can also help to minimize human allergic reactions to pets. A bath every two or three months is sufficient for most Chihuahuas, but don’t hesitate to do it more often if needed. Little dogs can become quite dirty if they spend a lot of time outdoors. Frequent bathing will not do him any harm as long as you use a mild pH-balanced dog shampoo and dry him carefully to prevent chilling.