Flea allergy dermatitis in dogs occurs when saliva from a flea bite sets off an allergic reaction that leads to intense itching. Integrative veterinarian Dr. Julie Buzby discusses the symptoms, diagnosis, treatment, and prevention of flea allergy dermatitis (FAD) to help you recognize and manage this common condition.
Flea allergy dermatitis (FAD) is the most commonly diagnosed allergic skin condition in dogs in the United States. Some estimates suggest as many as 40% of domestically owned dogs suffer with some degree of FAD.
It’s most prevalent in summer when flea activity is at its peak. However, in warm, humid climates like the southeastern United States, FAD can be a year-round battle.
What is flea allergy dermatitis in dogs?
Flea allergy dermatitis in dogs is a hypersensitivity reaction (allergy) to specific proteins in a flea’s saliva. When a flea bites a dog, it will inject a small amount of protein from its salivary glands into the skin. These tiny proteins trigger the immune system to mount an allergic reaction in dogs with a flea saliva allergy. The end result is a cascade of unpleasant symptoms and an overwhelming feeling of itchiness and discomfort.
It is important to note that the culprit in flea allergy dermatitis is the flea’s saliva, not the presence of the flea itself. This means that in extremely sensitive dogs, a single flea bite can be enough to cause intense itching. On the other hand, a non-allergic dog can have a substantial flea infestation but not be nearly as itchy.
Any dog can develop signs of FAD, but it is most common in dogs who are 3-6 years old. Often, dogs who have flea allergy dermatitis also have other allergies such as seasonal allergies. This can sometimes make it more challenging to sort out whether the symptoms are due to FAD or a different allergy.
What are the symptoms of flea allergy dermatitis?
As you might expect, the main symptoms of flea allergy dermatitis center around the itching and skin irritation. They include:
Itching (pruritis)
Due to the allergic reaction, dogs with FAD are very itchy. Depending on the dog, the itchiness may start minutes to days after the flea bite. You might hear an affected dog scratching (even when he should be sleeping at night), see him chewing at the base of his tail or along his back or front legs (sort of like he’s nibbling corn off a cob), or notice him rubbing his body on the ground.
Hair loss (alopecia)
Affected dogs lose hair due to the excessive chewing and scratching. Some dogs develop a symmetric pattern of hair loss on the lower back near the base of the tail (and hair loss on the dog’s tail), down the back legs, and in the groin and belly area. In severe cases though, dogs may have generalized hair loss that also includes the chest, front legs, collar area (around the neck), and behind the ears.
Skin redness (erythema) and warmth
Dogs with FAD may have a red rash on the back or belly. But they can also have generalized redness that covers the entire body. Due to the inflammation, the skin often feels warmer than normal.
Thickened skin (lichenification)
Chronic irritation can lead to leathery or thick skin, especially in the areas where the itching is the worst.
Skin infection (dermatitis)
When the outer epithelial barrier of the skin is damaged by scratching and chewing, organisms like yeast and bacteria flourish in the unhealthy tissue. This leads to secondary yeast or bacterial skin infections (pyoderma in dogs) or hot spots in dogs. Dogs may develop pustules, scabs, and crusts on the skin, which often require veterinary care to resolve.
Indirect results of flea infestations
Additionally, while not directly related to flea allergies in dogs, these less common symptoms of fleas are worth noting:
- Tapeworms —When a dog swallows an adult flea, which usually happens inadvertently as the dog chews at an itchy spot on his or her skin, he or she may also ingest the larvae of the tapeworm Dipylidium caninum within the flea’s digestive tract. The larvae attach to the dog’s intestinal wall and grow. Eventually, egg-containing tapeworm segments pass in the dog’s feces. These segments often look like dried grains of rice that are stuck to the fur around the dog’s anus. Or you may see them in the feces.
- Anemia—Dogs (especially young puppies or sick or malnourished adults) with a severe flea infestation can develop anemia in dogs. A dog with flea bite anemia will be weak and lethargic with pale white gums. If you see those signs, make an emergency vet visit.
- Other flea-borne diseases—Fleas can carry other organisms that can cause life-threatening illnesses, not just to dogs but also to people. A few well-known diseases include plague (yes, just like in medieval times), typhoid fever, and cat scratch fever.
How can you know if your dogs has fleas?
If your dog is showing some of the symptoms above, figuring out if your dog has fleas is a good place to start. You may see live fleas scurrying through the fur if you gently brush your dog’s coat in the wrong direction. However, because it doesn’t take many flea bites for your dog to start developing flea allergy dermatitis symptoms, and because dogs sometimes swallow the offending flea when biting at the skin, you may not actually find any adult fleas.
In the absence of live fleas, you may still find flea dirt (flea feces) in your dog’s fur. Flea dirt looks like little brownish-black specks, sometimes having a curlicue shape. If you comb flea dirt off your dog and moisten it on a white paper towel, it will dissolve and turn red because flea dirt is actually digested blood.
Less commonly (and in my experience, usually with very severe flea infestations), combing through the fur with a flea comb can yield live adult fleas, flea dirt, and tiny white particles that look like sand, but are actually flea eggs. (Remember though—dogs with FAD may not necessarily have a large flea infestation.)
How will the vet diagnose flea allergy dermatitis in dogs?
It is also important to involve your veterinarian, especially if your dog’s skin is irritated, you don’t already have a veterinarian-prescribed flea medication for your dog, or your dog’s symptoms are severe.
During the appointment, the veterinarian will start by asking you questions about if your dog is already on a flea preventive (and if so, which product and when the last dose was), what sort of symptoms you are seeing, if you have found any evidence of fleas, etc. Then he or she will look for fleas and flea dirt and carefully examine any areas of irritated skin. If the signs fit, the vet may diagnose your dog with FAD. Improvement of the signs once you start an effective flea control program help confirm the diagnosis.
In more complicated cases, the vet may recommend intradermal skin tests or blood tests for allergies to flea saliva. However, it is important to know that only approximately 80% of dogs with FAD will test positive on intradermal testing. While performing the allergy tests for flea saliva, the vet or veterinary dermatologist will often test for other environmental allergies since dogs with flea allergies tend to have seasonal allergies too.
What is the treatment for flea allergy dermatitis?
Treating flea allergies in dogs is often a multistep process. The goals are to get rid of the existing fleas, manage the infection and itching, and minimize future flea bites.
Get rid of existing fleas on your dog
First and foremost, you want to get the live fleas off your dog as quickly as possible. This can be achieved with over-the-counter (OTC) products or veterinary products.
Using over-the-counter product to treat flea allergy dermatitis at home
If you are waiting for a vet appointment, you may want to start treating flea allergy dermatitis at home. Many OTC shampoos and sprays are available in more natural formulations, which are safer and more environmentally-friendly alternatives to traditional pest control products.
Additionally, Capstar® (nitenpyram), is a short-acting oral tablet that kills live fleas on your dog for a 24-hour period. It does not require a prescription and can be given on consecutive days as needed in severe infestations.
However, it is still best to check with your vet before using any of these short-acting products on your dog. Also, do NOT apply any long-lasting OTC flea preventives to your dog. They can be ineffective or sometimes even dangerous. Instead, purchase a safe and effective long-acting product from your veterinarian.
Using veterinary products to treat FAD
Your veterinarian can also prescribe products to get rid of fleas both now and in the future. Many oral and topical veterinary flea preventives start killing fleas rapidly—within minutes or hours. And they last for one to three months to provide continued protection. (More on these products soon)
Control flea life stages in the environment
The adult fleas you see are only the tip of the iceberg. There are also flea eggs, pupae, and larvae hiding in your carpet, couch, and other places around your home. Thus, treating your home and yard is equally important in completely eradicating a flea infestation. Options include:
- Borate-based powders like Flea Busters®—These products kill live fleas and flea larvae by acting as a desiccant. The powder granules cling to fleas and larvae in carpet fibers and bedding, causing them to die from dehydration.
- Environmentally-friendly indoor and outdoor sprays (like Wondercide™)
- Vacuuming carpets and floors regularly and then throwing away the vacuum bag or emptying the canister immediately.
- Laundering your dog’s bedding in hot water, especially if you see flea dirt.
Soothe your dog’s flea allergy dermatitis symptoms
In addition to helping you tackle fleas on your dog and in your home, your veterinarian will make recommendations for decreasing your dog’s FAD symptoms.
Manage secondary skin infections
If your dog has skin lesions (pustules, scabs, or hot spots), your veterinarian may prescribe a short course of oral antibiotics. Plus, he or she may also recommend using topical creams or sprays designed to decrease bacteria or yeast populations, relieve itch, and soothe inflammation.
Decrease itching
It is also important to take steps to decrease itching. In the past, the options were to start the dog on a short course of steroids or try OTC antihistamines.
Prednisone for dogs, a popular oral steroid, is a very effective at rapidly providing short-term relief of itching and inflammation. However, higher doses and long-term use of steroids can lead to unwanted side effects and unintended health complications.
Human antihistamines like Benadryl for dogs, Chlorpheniramine, Zyrtec® and Claritin® don’t tend to be strong enough for anything but mild FAD.
In the last few years, two new allergy medications for dogs, Apoquel® and Cytopoint®, have come onto the scene. Both provide a safe and effective way to control itching from FAD without steroids. Apoquel comes in a tablet form and can be given in a short course or for more extended periods as necessary. Cytopoint is an injectable medication that your veterinarian must administer in the clinic. One dose gives 4-8 weeks of relief from itching.
Keep in mind that the function of these medications is to reduce itching while you work with your veterinarian to identify and eliminate the allergic triggers—flea bites.
Create a plan to kill fleas on your dog going forward
Your veterinarian will also help you make a plan for year-round flea prevention for ALL pets in your home. While it clearly makes sense to treat your allergic dog, other pets in the home who aren’t flea allergic must also be on flea prevention. Otherwise, they could carry fleas in from outside, reintroducing fleas to your home and your allergic dog.
There are several excellent prescription flea control options available through your veterinarian. Many of these products also protect against ticks, heartworm disease in dogs, and certain intestinal parasites. This gives you the option of “one-stop shopping” to ensure additional protection for your pets.
As mentioned earlier, it is recommended to use prescription products rather than taking a chance with an over-the-counter product. While OTC products are often less expensive, most are ineffective, and many can be dangerous.
Finding the right product
When helping you select a flea preventive to manage and treat flea allergy dermatitis, the veterinarian will take speed of kill into consideration. The faster a flea dies, the less often it can bite your dog. This makes a difference when every bite transfers allergens into the dog’s skin. Additionally, products with an insect growth regulator (helps break flea lifecycle) as well as an an adulticide (kills adult fleas on the dog) can provide better, faster control of fleas.
The vet will also help you decide if a topical liquid or chewable table would be the best form for the flea preventive.
Some dogs don’t like the smell of certain chews and will refuse to eat them or spit them out as soon as you’re out of sight. Other dogs may ingest the chew tablet but experience vomiting. In these cases, a topical product may be the better option.
Conversely, if your dog has severe skin inflammation or infection, applying anything topically can be incredibly irritating. Or other dog parents may prefer not to have anything on the dog’s skin that children or other pets could come in contact with. In those cases, opting for a chewable tablet would be better.
Don’t give up if you still see fleas or FAD signs in the first three months of treatment
Because of the length of the flea lifecycle and the fact that some environmental life stages are difficult to kill, it may take three months to fully eradicate the fleas. If your dog periodically has fleas or flares of FAD in that time, it doesn’t mean the treatment isn’t working. Instead, a new crop of fleas has probably emerged that now need to get killed.
What is the prognosis for dogs with flea allergy dermatitis?
The long-term prognosis for dogs affected by flea allergy dermatitis is usually good with effective treatment and consistent use of flea control. That said, if you live in a warm, humid climate, you may have a year-round battle with fleas.
The thing to keep in mind is that if your dog has FAD, it is important to be proactive in preventing future flare ups.
How do you prevent future episodes of FAD?
Treatment of flea allergy dermatitis and prevention of future episodes are tied closely to one another. The following five prevention tips can be helpful if you have had flea allergy dermatitis diagnosed in your dog.
1. Use effective veterinarian-prescribed flea control on ALL pets ALL year long
Year-round flea control is key to preventing flea allergy dermatitis in your dog. This includes consistently treating your allergic dog and any other pets in the home. Let me say it again. Treat ALL pets in the home on a year-round basis. Otherwise, you’ll be chasing the flea cycle in a never-ending circle if an unprotected pet brings new flea friends in from outside.
2. Partner with your veterinarian for trouble-shooting
If you feel like your dog’s flea preventive product isn’t working or your dog keeps getting flare ups of itchy irritated skin, reach out to your veterinarian. He or she can help you trouble shoot.
Maybe the vet will have you try a new flea product or approach to flea control. Or he or she might examine your dog and determine that this time a condition like environmental allergies, mites, or other skin problem could be to blame for your dogs symptoms instead of FAD.
3. Have a regular cleaning routine to decrease the chances of flea life stages living in your home
Additionally, your cleaning routine should include frequent vacuuming. (Pro tip: Place an inexpensive flea collar in your vacuum bag or cylinder to kill any live fleas that get sucked up.) Plus, it is a good idea to regularly launder your dog’s blankets and bedding.
4. Manage fleas outside the home too
Use a flea product to treat any outdoor spaces where your dog likes to hang out (flower beds, beneath decks, shaded areas). Also, keep trash bins and livestock food bins securely closed to discourage rodent activity around the perimeter of your home and yard. This is helpful because rodents commonly carry fleas.
5. Consider hiring a pest control professional
For those infestations that seem impossible to overcome, consider hiring a professional pest control service to treat your home and yard. Many pest control companies now use products that are effective and safe for use with pets and small children on the premises.
However, it’s always a good idea to verify the safety of their products with their team before the service call. A reputable pest control company should not hesitate to provide you with MSDS safety sheets for the products they plan to use on your property.
Check your dog regularly for fleas
Check your pets regularly for signs of flea activity by incorporating it into your dog’s weekly tip-to-tail wellness scan.
Remember, it only takes ONE bite from a flea to make a flea allergic dog miserable. Save yourself the headache of trying to control a flea infestation and save your dog the discomfort of FAD by having all pets on effective veterinary-prescribed flea prevention all year long. This is definitely a time when an ounce of prevention is worth a pound of cure!
Does your dog have flea allergy dermatitis?
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