If a dog has fleas, the owner must first give it a bath. Bathing can remove 90% of adult fleas. You can use liquid flea lotion from the pet hospital for external use and drop it on the hairless area behind the ears. For dogs who don't like bathing, you can use flea powder on them. Sprinkle the flea powder on the hair behind the ears, abdomen and legs where fleas may be present.