Flea Allergy Dermatitis (FAD) in Dogs

Fleas are very common ectoparasites that feed on our furry friends' blood at any age. Able to infest them at practically any time of year, we need to know the measures to prevent them from attacking and spreading. These insects aren't just a cosmetic nuisance, since they can transmit other parasites like tapeworm, or cause health problems like anemia or flea bite allergy dermatitis, which we'll cover below.

It's also worth pointing out that fleas can affect us, humans, too. They don't usually transmit diseases to us, but their bite is uncomfortable on its own, and it can be followed by bacterial infections.

What Is FAD?

Flea allergy dermatitis is the most common allergy in dogs. Like any allergy, it happens when the immune system overreacts to a stimulus that, in principle, shouldn't be dangerous. In this case, the hypersensitivity reaction occurs against protein fractions present in the enzymes, polypeptides, amino acids, and aromatic compounds in flea saliva, injected into the animal at the moment of the bite. This saliva is injected to prevent blood clotting while the flea feeds.

We should also know that the reaction can appear right at the moment of the bite, or persist for some time after. This explains why the dog can show lesions even when we don't find a trace of fleas. A single bite is enough to trigger the reaction.

Symptoms of FAD

Since this is a reaction caused by fleas, we might assume it's limited to the time of year when parasites are most present. However, the environment inside homes manages to keep optimal living conditions for these insects, so we can find them any month of the year.

The clinical picture is characterized by the following signs:

1. Pruritus (intense itching) — the dog will nibble at the affected areas.
2. Hair loss from scratching.
3. Erythema (redness of the skin).
4. Red bumps that look like small pimples.
5. Lesions appear on the lower back, the base of the tail, the groin, armpits, neck, between the toes, and the abdomen — the areas with the highest flea concentration.
6. In more severe cases, we'll see open wounds, followed by scabbing. They can also become infected.
7. Over time, the skin thickens and darkens.
8. Due to the discomfort, the animal may show loss of appetite, stress, nervousness, listlessness, or sadness.

How Is FAD Diagnosed?

Generally, this allergy is diagnosed through symptoms and directly spotting fleas or their remains on the animal or its environment. If we can't find the insects, the clinical picture is usually enough for the vet to suspect FAD.

In this case, they'll prescribe a treatment. If it works, we'll consider the diagnosis confirmed. We can also confirm this diagnosis through in vitro antibody allergy tests or intradermal skin testing.

Otherwise, the vet will keep looking for the cause, since FAD symptoms can be confused with other skin conditions, such as atopic dermatitis, food allergies or intolerances, sarcoptic mange, Malassezia, cheyletiellosis, bacterial folliculitis, or an adverse drug reaction.

It's worth noting that it's essential to be able to tell apart the lesions caused by a flea infestation (parasitism by a very large number of fleas), where skin irritation is proportional to the number of fleas, from FAD, where just one flea bite is enough to trigger the allergic reaction.

Can FAD Be Cured?

The flea allergy itself doesn't go away, but if the dog doesn't come into contact with these parasites, it won't show symptoms. So, preventive anti-parasite treatment is the most effective remedy. This needs to be thorough, applied to the environment as well, year-round, and to every animal in the home.

The lesions caused by this allergy may need treatment with antihistamines or corticosteroids to relieve the itching. In addition, nowadays we also have other treatments like Apoquel, an innovative drug with a fast effect and without the side effects associated with corticosteroids. It may also be advisable to give topical or oral antibiotics in cases complicated by bacterial infection.

Remedies to Prevent FAD

Preventing fleas from coming into contact with the dog will be our top priority. To achieve this, we need to understand that we have to eliminate the fleas found on the dog, but also those in the environment, which actually make up about 95% of the total.

So, besides applying anti-parasite treatments to every animal in the home and eliminating adult fleas, we need to handle cleaning the environment and preventing eggs from developing. We'll follow these guidelines, always using products prescribed by the vet:

• Carry out proper external and internal deworming for every animal in the home.
• Products should have a preventive effect, meaning they protect the dog for weeks, and it's recommended they also inhibit egg growth, which is essential for eliminating the parasite load in the environment.
• Carefully follow the vet's recommendations when applying anti-parasite products, to ensure their effectiveness. That said, none will be 100% effective.
• It's a good idea to use a comb to manually remove any fleas we can.
• Wash bedding in the washing machine at high temperatures.
• Vacuum the house thoroughly and dispose of the bag right away, if applicable.
• Clean with anti-flea products, paying special attention to cracks and crevices. Steam cleaning is very effective.
• In severe infestations, we can use so-called flea bombs (foggers), which kill fleas hiding in the environment.

Lastly, fleas are a somewhat tedious insect to eradicate, but with thorough control, proper prevention, and following our regular vet's guidance, we won't have any problems!