There are a number of ways to check for fleas on a dog: observing changes in behavior, combing to look for flea dirt, finding tapeworm segments or larvae and noting hair loss. Fleas not only infect dogs, but they also invade their environment, such as their bedding and feeding area. Infected dogs require prompt treatment; fleas promote anemia and affect humans as well.
Dogs with fleas exhibit a number of physical characteristics. They often have skin sores with oozing pus and patches of lost hair. Fleas also promote the presence of tape worms. Tape worm segments and larvae are visible around the dog's anus and in his stool. Tape worm larvae has the appearance of rice.
In response to the itching caused by fleas, dogs perform several observable activities. They scratch, chew, lick and bite themselves. They rub their bodies against available surfaces. These acts of self-mutilation leave skin sores, which are often red, raw and bloody.
In severe infections, fleas are visible jumping on and off the body of an infected dog. Owners find fleas by turning a dog onto his back and checking the groin, armpit and other warm, moist areas. A flea comb is very useful. Passing it through the hair of a dog's back and legs catches fleas that are secluded in hiding spots.