Fleas On Your Dog: Tiny Parasites That Can Cause Big Problems
By Rachele Baker, DVM – Fleas are the most common external parasites of dogs. Although these parasites are only about an eighth of an inch long, they can cause big problems for your dog. Fleas have piercing, sucking mouthparts that they insert through the skin to obtain blood meals. Flea bites irritate the skin. Flea saliva contains antigens that can cause allergic skin reactions in dogs with allergies to flea bites.
Dogs with allergies to environmental allergens such as pollen and grasses (atopy) are frequently allergic to flea bites as well. Dogs that are allergic to flea bites are hypersensitive to the antigens in flea saliva. Allergy tests have shown that approximately eighty percent of dogs with atopy are also allergic to flea bites.
As a veterinarian, I see many dogs for itching and skin problems caused by fleas. Pet parents frequently insist that their dog does not have fleas because they have never seen fleas on their dog.
Dogs that suffer from allergies to flea bites are extremely sensitive to them. Just one flea bite can cause intense itching in an allergic dog for up to five days. When a flea bites an allergic dog, the dog will lick and chew that area and will either ingest the flea or cause it to jump off. This explains why many pet parents have not seen fleas on their dog even though fleas have been present.
Those Tiny Fleas Can Cause Big Problems
In addition to causing extreme itching and discomfort, flea bites can lead to serious skin problems. A dog with flea allergies that is being bitten by fleas will itch, scratch, and chew their skin. The dog will typically scratch and chew the back half of his or her body including the rump, belly, back legs, and tail base. This can result in hot spots (reddened, infected areas), hair loss, rashes, and secondary infections.
A dog that goes untreated for fleas will continue to chronically lick and chew his or her skin. This can cause the skin to become lichenified (thickened and leathery with exaggerated skin markings) and/or hyperpigmented (darkened).
Another problem that can result from flea infestations is tapeworm infection. Pet parents may notice tiny white worms around their dog’s rectum or on their dog’s stool. These tiny white worms that resemble grains of rice are tapeworms (Dipylidium caninum). The only way that dogs can become infected with tapeworms is by ingesting infected fleas which can occur when they are chewing, licking, or grooming themselves. So even if a pet parent has never seen fleas on their dog, if their dog has tapeworms, then fleas have definitely been present on their dog.
Fleas, Eggs, Larvae, and Pupae In Your House and Yard
There are more than 2000 species of fleas in the world. The “cat flea” (Ctenocephalides felis), is the most common flea found on both dogs and cats. The information presented here is about “cat fleas.”
Adult fleas spend their life on their host (dog, cat, or other animal). They can survive for more than one hundred days. Female fleas start producing eggs within 24-36 hours after they take their first blood meal from their host. They can continue to produce 40-50 eggs per day their entire life. This can result in rapid, exponential increases in flea populations in an environment. Here is a graphic that I created illustrating the flea life cycle:
Fleas lay eggs on a dog’s skin. The eggs then roll off the dog throughout the house and yard. The largest number of eggs will be deposited in places where the dog spends most of his or her time. Opossums, raccoons, foxes, coyotes, and stray dogs and cats traveling through the neighborhood also distribute flea eggs into the environment.
If a dog is parasitized by fleas, then it is very likely that significant numbers of fleas, eggs, larvae, and pupae are present in their house and yard. It requires time and diligence to successfully eliminate adult fleas and immature stages from a flea-infested dog, house, and yard.
Signs Your Dog May Have Fleas
A dog with allergies to fleas will suffer intense itching from flea bites. As noted above, the typical areas that dogs with fleas will itch and scratch are anywhere on the back half of the body including their rump, belly, back legs, and tail base. Hotspots may develop on the dog’s rump or on the side of his or her face. Rashes may develop on the dog’s belly.
To look for fleas on your dog, part the hair and look at the skin on the rump. Another good area to look for fleas is your dog’s belly since that area is usually hairless. You can also use a specially designed comb called a “flea comb” to search for fleas on your dog’s rump. Even if live fleas are not found, “flea dirt” may be observed. “Flea dirt” is the term used for flea feces (stool). Flea dirt looks like tiny dark brown particles on the skin at the base of the hair shafts. If flea dirt is seen on a dog, then fleas have been present.
Flea feces contain digested blood. To confirm that particles found in your dog’s fur are flea feces, use a flea comb to collect some of the particles. Then place the particles on a white paper towel and slightly moisten them. Flea feces will leach a reddish color onto the paper towel which is digested blood.
However, even if no fleas or flea dirt can be found on your dog, that does not mean that he or she has not been parasitized by fleas. If your dog is scratching and chewing areas of his or her body typical of flea infestations, then it is likely that there have been fleas on your dog and that there are fleas in your house and yard. If your dog’s itching and scratching resolves after treatment for fleas, it reasonable to assume that flea bites were the cause of your dog’s discomfort.
Eliminating Fleas From Your Dog, Your House, and Your Yard
Flea control products available for dogs include oral and topical treatments as well as flea collars. I have compiled several tables comparing select oral and topical flea control products. I have designed these tables to help pet parents decide which product is best for their dog. I have also included information on select flea collars below the tables. You can view these tables on my page entitled Flea and Tick Control Products For Dogs. Not all flea control products are safe or effective. It is important to use good quality, reputable products to treat your dog. Your veterinarian is the best source of these products.
It can take up to three months to completely eliminate adult fleas and immature stages from your house and yard. Immature stages in the house and yard will continue to develop and adult fleas will continue to emerge. So fleas may still be seen on pets in the household for a number of weeks after flea treatment has begun. However, any newly emerged fleas that jump onto pets will be killed by the flea control product used. This will result in breaking the flea life cycle and eventually eliminating fleas and immature stages from the environment.
Studies using the topical flea control products Frontline, Advantage, and Revolution to treat household pets have demonstrated that the use of these products alone was 95-100% effective in eliminating flea populations from both the household pets and their environment (house and yard).
In order to break the flea life cycle and eliminate fleas and immature stages from the environment, it is recommended that flea control products be used every month year round for all dogs and cats in the household.
Regular and thorough vacuuming will remove adult fleas and immature stages in the house. Pay special attention to baseboards and areas frequented by pets. Wash all pet bedding and throw rugs regularly.
It may be necessary for pet parents to hire a professional exterminator to treat the house and yard if flea infestations are severe. In addition, it is helpful to keep grass cut short and to regularly remove leaves and brush from the yard.
Treating Your Dog’s Itch and Secondary Skin Infections
You should take your dog to see your veterinarian if your dog is itching and scratching and you suspect that your dog is suffering from allergies to flea bites. If your dog has hot spots, rashes, or other evidence of secondary skin infections, take your dog to see your veterinarian right away. Your veterinarian may prescribe various medications or topical treatments to relieve itching and to treat secondary skin infections.
I strongly recommend bathing a dog suffering from flea bites to remove the fleas and flea dirt and soothe the skin. I do not recommend flea shampoos because they can be toxic and they can also dry the skin which can worsen the itching. Any shampoo will kill fleas on a dog. If secondary skin infections have not developed, I recommend shampoos designed to soothe the skin such as Douxo Calm Shampoo or DermAllay Oatmeal Shampoo. Douxo Calm Micro-Emulsion spray can be applied to the dog’s skin after bathing to relieve inflammation and soothe the skin. Please see my page entitled High Quality Shampoos, Sprays, and Wipes For Dogs With Allergies for more information about these products.
If secondary skin infections have developed, I recommend medicated shampoos such as Malaseb or Douxo Chlorhexidine PS Shampoo. Please see my page entitled High Quality Shampoos, Sprays, and Wipes For Dogs With Allergies for more information about these products.
In conclusion, fleas, although tiny, can cause big problems for your dog including extreme itching and skin problems. Consistent, monthly use of good quality flea control products can prevent fleas from infesting your dog, your home, and your yard.