HOW TO CONTROL AND PREVENT FLEAS ON YOUR DOG Dr. Doug Brum General Practice Preventative Medicine UNDERSTANDING THE FLEA For millions of pets and people, the tiny flea is a remorseless enemy. The flea is a small, brown, wingless insect that uses specialized mouthparts to pierce the skin and siphon blood. When a flea bites your dog, it injects a small amount of saliva into the skin to prevent blood coagulation.