When you want to know if your dog has fleas, check his fur for flea dirt. Do this by brushing his coat out over a light-colored towel or piece of paper. Dampen any black specks you find with a drop of water. Alternatively, you can smear them with a moist cotton ball. If they are flea dirt, these specks will turn red. Then you'll have to pick the fleas out of your dog's fur with a fine-toothed flea comb. Dip the comb in a bowl of soapy water periodically. The soap will hold down the fleas so they can't escape, and the water will drown them.
Pay attention to your dog's reaction as you comb or brush him. If he flinches when you touch a particular spot, you should examine that area for any lumps or sores. Make a note of the sore spot's appearance. For example, is it a hard or soft lump? Is the spot rough? Is it oozing?
If you do find fleas or other skin problems on your dog, let your veterinarian know. He or she can give you advice on what treatments or dog-care products are best for your dog. He will probably want to put your dog in a flea dip. Natural alternatives include adding brewer's yeast or garlic to your dog's food. You'll probably want to use pills, a flea collar or a topical treatment to prevent the fleas from returning. You can also try a homemade flea powder made of eucalyptus, rosemary, fennel, yellow dock, wormwood or rue.
Aside from finding the fleas on your dog, another way to tell if you have fleas in your house is with a flea trap. Simply hang a light source over some flypaper or a bowl of soapy water. The fleas will be attracted to the light source and they'll get stuck on the paper or in the water.