Exposure to wetness, whether it be from a bath, swimming or your dog's curious tongue, can cause infection. Many experts say that you should not bathe your dog for at least one week after neutering, while others say to wait 10 to 14 days, since the sutures will not fully heal until then.
Cleanliness Prevents Infection
Even if a dog has an Elizabethan collar around its neck to prevent it from accessing the stitched skin with its tongue or teeth, it may still be able to infect the wound by rubbing it against a surface. To avoid the stitches' being potentially contaminated with bacteria, you have to clean the dog in order to prevent complications.
Since you should not be bathing your dog more often than every six weeks anyway, refrain from bathing your dog for at least two weeks after the surgery. If absolutely necessary, clean your dog's hair using a dry bath. If the wound gets dirty, disinfect it with warm, salty water and dry thoroughly, or see your vet.