Whether or not your dog can have a bath after you’ve used flea medication on him depends on the type of medication that you’ve used. Sprays and powders are more likely to be affected by bathing than once-a-month spot treatments. Some general guidelines apply, but for detailed information read the product label to see what the manufacturer says about the specific treatment you’ve chosen.
Spot treatments go on your dog’s back between his shoulder blades and are normally applied only once per month. You’re safe to give your dog a bath once the medication has completely dried, typically in about 24 hours. It’s OK to wait longer than that, but bathing him too soon will wash away some of the medication and decrease its effectiveness.
Sprays and Powders
Most sprays and powders will wash off when you give your dog a bath. Instead of bathing your dog after application, wash him before you treat him and then apply the spray or powder according to the manufacturer’s directions. If you bathe your dog he will most likely need to be retreated for fleas.