Flea Bites on Dogs: What Do They Look Like?

Published Jan. 5, 2017

By Mindy Cohan, VMD

Learning that your pet has fleas is extremely disconcerting. Many pet parents become worried that a flea infestation implies poor housekeeping. Others are disgusted by the fact that these pests are living on furniture, beds, carpets and hardwood floors. Upon discovering a flea problem, immediate action must be taken.

Start by Finding the “Flea Dirt”

The crucial first step is to identify whether or not you truly have a flea problem. Adult fleas are visible to the naked eye, but they are tiny and move quickly. In the early stages of infestation, you might not be able to find adult fleas on your dog. Instead, flea feces, also known as “flea dirt” are often the tell tale sign. Fleas feed on your pet’s blood, accounting for why their deposits contain digested blood.

Flea feces are easily visualized on light colored dogs, but it is far more difficult to detect flea dirt on dogs who are dark in color. Running a fine-toothed flea comb through your pet’s fur will easily pick up pieces of flea dirt as well as adult fleas that are present. Flea dirt resembles ground pepper and is often mistaken for specks of dirt. You can discern flea dirt from actual dirt by placing the material on a damp white tissue or paper towel.  Moistened flea dirt will reveal a reddish-rust color on the towel or tissue which represents the pet’s blood ingested by the flea.

Rule Out Other Types of Bites

Detecting fleas or their feces provides a definitive diagnosis, but suspicion of a flea problem can be raised if you observe your dog biting or scratching. Some dogs are allergic to fleas and will become extremely itchy from the bites of as few as one to two fleas. In these cases, fleas or flea dirt may not be evident at all since the dog’s intense biting, licking and scratching can obscure the evidence that fleas are present.

It is a common misconception that dogs scratch due to fleas walking on their skin. The basis for a flea bite allergy is actually the flea saliva which enters a dog’s body as a flea takes a blood meal. Although dogs can become itchy anywhere on their bodies, the most commonly affected areas include the hind legs, the groin, and the skin on the back between a dog’s ribcage and tail. Not all dogs are allergic to flea saliva, so the absence of itchiness does not rule out a flea problem.

Flea bites are often inconspicuous on dogs with thick coats. To check your dog, examine less densely furred areas such as the groin and armpits for signs of small, raised areas of redness associated with a flea bite.

It is not easy to discern a flea bite from that of a mosquito or other insect since most bug bites produce a similar area of localized redness with possible swelling. However, mosquito bites are usually solitary, can occur anywhere on the body, take longer to resolve than flea bites, and occur in warmer climates. Flea bites can occur anytime of the day as opposed to primarily at dusk and even when the outside temperature is cold if the fleas are thriving in your warm home.

Finding a tick attached to your dog’s skin is the easiest way to discern a tick bite from a flea bite. Since tick bites also appear as subtle small red lesions, they often have a similar appearance to the reactions created by biting fleas and mosquitoes. Tick bites, however, can sometimes develop a “bull’s eye” appearance and are more likely to develop a scab or raised sore compared to the bites of fleas and mosquitoes. But, scabs can develop at the site of flea and mosquito bites secondary to the the skin trauma caused by scratching or biting.

Fleas can seek blood meals from both pets and people. Since flea bites on dogs are usually inconspicuous, veterinarians may diagnose a flea problem based upon the aforementioned distribution of itchiness and the complaint of bites and itchiness in the human household members. Similar to dogs, not all people are reactive to flea bites. However, pet parents with a flea bite hypersensitivity will develop small, red skin lesions that are itchy. Flea bites tend to occur in clusters, particularly around a person’s ankles. In the absence of fleas, flea dirt and an itchy dog, allergic pet parents often serve as the sentinel for a flea diagnosis.

What to Do Once You’ve Confirmed Your Dog Has Fleas

Once you have confirmed a flea infestation, you need to address both your home environment and pet. 

What Kills Fleas on Dogs Instantly?

Bathing your pet is a desirable first step for dogs with a moderate amount of flea dirt in their coats. Keep in mind that while flea shampoos are good at removing flea dirt and adult fleas from your pet’s skin and coat, they do almost nothing to prevent fleas that are in the environment from reinfesting your dog. If you shampoo your dog and plan to use a topical flea product, be sure to read the instruction label carefully. The application of several topical flea prevention products is not recommended within two days of bathing.

There are many effective products available that will kill adult fleas on your pet and prevent new fleas from biting and continuing their lifecycle for a month or more, including collars, oral medications and the aforementioned topical products. Consult your veterinarian for recommendations best suited to your dog that are aimed at controlling adult and immature fleas. If you also have cats, be sure to use a product labeled for cats. Many dog products can be harmful if applied to a cat. All pets in your home have to be treated for fleas if you are going to completely eradicate the infestation.

In addition to treating all of your pets, the home environment is a priority. Thorough every-other-day vacuuming and weekly washing of all bedding is necessary for several weeks if a home is severely infested. Hiring an exterminator is an option if you need additional help. Be sure to notify the exterminator of all types of pets in your home including fish, birds and reptiles to ensure their safety.

Being diligent about your pets’ flea control is imperative for preventing a problem in the first place. If you fall behind, or if your best efforts are not foolproof, don’t delay. Attack the problem immediately. Your veterinarian is an ideal resource for both advice and products. Combating a flea infestation with inferior products is extremely frustrating and time consuming, but with patience, perseverance and the right types of treatments, you will prevail.

Looking for more flea information? Visit our flea and tick survival guide.

Mindy A. Cohan, VMD


Mindy A. Cohan, VMD


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