Symptoms of Fleas on Dogs

By Elizabeth Xu

Fleas are tiny little pests that can cause big problems for your dog. Once fleas are on your dog they can cause a number of problems, and after they enter your home they might even feast on you. The prevention of fleas is important, and flea treatment should happen in a timely manner, but these parasites are so small that sometimes they can be tricky to spot.

Here are some symptoms of fleas on dogs that you should watch out for.

Scratching is usually one common indicator of fleas, but you can’t assume that your dog doesn’t have fleas just because there’s no scratching. Some dogs are very sensitive to flea bites and will scratch incessantly. Others are more tolerant and will be virtually covered with fleas but will scratch very little. There are other symptoms you should know about, especially since fleas are so small that you can’t necessarily trust your eyes, says Danel Grimmett, DVM, of Sunset Veterinary Clinic in Oklahoma.

“Fleas are sneaky. So many times I bring up the subject of fleas and see the owner physically bristle and tell me they haven’t seen any,” she says. “By the time most people see a flea, if they ever do, their pet will most likely be covered in dozens, if not hundreds, of the creatures.”

If your dog is gnawing or biting, especially at the top side of the base of their tail, they should definitely be evaluated for fleas.

“If you see a dog gnawing at that area, it’s always wise to just run a flea comb through the fur at the base of the tail, running up the lower part of the spine,” says John Clark, DVM, of Community Veterinary Clinic in Florida, noting that the base of the tail is a prime spot for fleas, likely due to the moisture in that area.

Gnawing or scratching can often lead to another tell-tale sign of fleas, says Grimmett—hair loss or matted hair. Usually once the fleas are gone the hair will grow back, but sometimes there are more lasting effects, she says.

“Sometimes such severe trauma has occurred that the resulting scars can be seen over the lifetime of the dog,” Grimmett says. “Deep scaring is often the result of the pet traumatizing itself because of the severe itching.”

Although it’s not a guarantee, a dog with fleas will sometimes show visible signs on their skin. Clark says “little red marks” on the base of the tail are one symptom of flea bites, and that a more generalized redness can occur if the dog scratches himself a lot.

A dog with a flea allergy or numerous fleas might have scabs or wounds on their skin, says Eva Evans, DVM, a veterinarian in Tennessee.

These symptoms can become serious if not taken care of, Grimmett says, noting that bacterial infections can also occur.

Another possible indication of fleas is the presence of what looks like dried coffee grounds on the skin, Grimmett says. Dog owners might just think their pet is extra dirty, but that stuff is actually flea feces containing digested blood. Try putting a little bit on a white sheet of paper and adding a drop of water. The liquid will start to turn red.

Although fleas don’t target a dog’s gums, signs of fleas can still be present there. Clark says dogs with a severe flea problem may lose so much blood that they get anemia, which can cause a dog’s gums to become white or pale pink. Evans says severe anemia can be fatal, especially in puppies.

Not all symptoms of fleas on dogs are physical—a flea infestation can make dogs act differently, too. Sometimes dogs can be cranky, restless or just plain acting odd, Grimmett says.

“Imagine having small bugs crawling all over you, biting you, making you terribly itchy day and night and not having any way to communicate your misery? Wouldn’t you be tired and cranky?” she says.

It’s important to keep in mind that pets in the same household who have fleas might react differently, Clark says. “For some reason, some dogs are super sensitive to fleas and other dogs aren’t.” If one pet in the house has fleas, it’s safe to assume they all do, even if they aren’t all showing the same symptoms.

Flea prevention is much easier than eradicating many tiny fleas and their offspring from your dog and your home. There are several things you can do to prevent fleas, Evans says.

“The best, safest and most effective way is to use a prescription product from your veterinarian,” she says. “The over-the-counter medications can cause serious reactions and rarely ever actually work well. The prescription products are much safer and are fully effective. You can also prevent fleas by keeping your pet away from flea infested areas, but this is difficult because you can't always know what areas are infested with fleas.”

If your dog already has fleas, Evans recommends, putting all the dogs and cats in your home on an effective flea prevention product from your veterinarian, vacuuming your whole house (including upholstered furniture), laundering all pet and human bedding, and consulting with outdoor professionals to see what should be done to minimize fleas in your yard.