These small and flattened insects are not as common as fleas or ticks, but they are still agonizing annoyances for dogs. Biting and blood-sucking, these external parasites are fast movers but they do not travel back and forth between dogs and people. They limit their residence to either dogs or to people and spread through contact with lice-infested grooming tools or other dogs.

Lice flourish in less-than-hygienic environments, making puppies highly susceptible, especially if their mothers are already lice-infested. These parasites cause tender, intense itching that produces red, scabby areas on the skin. You'll notice nits or eggs stuck on the hair shafts and poor coat condition, but you can use flea shampoo remedies to rid your dog of these parasites.