Does My Itchy Dog Have Allergies or Fleas?

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Is your dog constantly scratching, licking, or biting at their skin? These are often warning signs of an itchy dog. And one of the most common causes of the incessant itch is either fleas or skin allergies. But how can you tell what’s causing your pup’s discomfort?

While itchy skin in dogs might seem like a minor irritation, it can have a huge impact on your pup’s sleep, comfort, and quality of life. So it’s important to get to the bottom of the question: “Why is my dog itching so much?“

In this guide, we’ll help you understand the signs of both fleas and skin allergies (including allergies to fleas). Plus, we’ll explain how to tell the difference and share simple steps to provide itch relief for your dog.

Why Is My Dog So Itchy: Is It Allergies or Fleas?

Both fleas and allergies may cause intense pruritus (itchiness) in dogs. The underlying mechanisms, however, are different. Yet, because the signs of these conditions often overlap, it can be difficult to determine the root cause of the issue.

Here’s a closer look at how fleas and allergies affect your dog’s skin and why they cause irritation.

Why Fleas Make Your Dog Itchy

Fleas are tiny parasitic insects that crawl through your dog’s fur and bite their skin, leaving behind red, itchy spots. The sensation of fleas crawling and biting is what causes dogs to itch. This can then trigger incessant scratching and chewing in most dogs.

Some dogs develop a heightened sensitivity to a protein in the flea’s saliva. This can lead to an allergic reaction known as Flea allergy dermatitis in dogs (FAD). In dogs with FAD, all it takes is a few flea bites to cause severe itchiness. In these cases, it’s important to address both the infestation and the allergy.

Why Skin Allergies Make Your Dog Itchy

Skin allergies in dogs occur when their immune system overreacts to a specific substance (or substances). These triggers, called allergens, can come from various sources, including:

• Environmental allergens such as pollen, dust mites, grass, or mold
• Food allergens can be any ingredient, however the most common are proteins like chicken, beef, or dairy
• Flea allergens related to sensitivity to flea saliva

Dogs with environmental allergies, also known as atopic dermatitis, often have a defective skin barrier, allowing allergens to penetrate the skin and cause itching. Similarly, food allergies can trigger itchiness, often accompanied by gastrointestinal symptoms like vomiting or diarrhea.

The immune system’s reaction to allergens releases chemicals like histamine, leading to skin inflammation, redness, and itching. Chronic scratching can also cause secondary skin infections, compounding the discomfort.

Other Causes of Itchy Skin in Dogs

While flea infestations and skin allergies are the most common causes of skin itchiness in dogs, other culprits could be:

• Bacterial skin infections (i.e., Staphylococcal dermatitis)
• Yeast skin infections (i.e., Malassezia dermatitis)
• Infestation with other skin parasites, such as mites or lice

Allergies or Fleas? How to Tell

It can be hard to pin down what’s causing your dog to itch. Some signs are common to both fleas and skin allergies. And dogs with a flea bite allergy will usually have signs of both fleas and skin allergies.

Below are some signs to look out for that may help you identify the culprit. But always work with your veterinarian to confirm the cause and correct treatment plan.

5 Common Signs of Fleas on Dogs

Fleas are the most common external parasite of dogs, and they’re found all over the world. If you’re wondering, “How can I tell if my dog has fleas?” look out for these common signs:

Depending on the geographic location, fleas are present on 5% to 100% of dogs in an area. With alarming numbers like these, you may be wondering—how do you know if a dog has fleas?

You can prepare yourself to identify a flea infestation by familiarizing yourself with the signs of fleas on dogs.

Common signs of fleas (when an allergy is not present) include:

1. Small red flea bites on the skin: These red bites from fleas may look like small pimples, raised dots, or a rash on your dog’s skin. Flea bites on dogs tend to appear in areas like the base of your dog’s tail, groin, or armpits.
2. Dark specks of “flea dirt” on the skin: Flea dirt on dogs isn’t actual dirt, though it can look like it (or, more commonly, like coffee grounds). It’s the term for blood that fleas digest and excrete on the skin near the base of your dog’s fur coat. To tell whether you’re dealing with dirt or flea poop, try to get some of the specks on a wet paper towel. If they turn red, it’s flea dirt.
3. Visible fleas crawling in the fur: Fleas are small, narrow, six-legged insects. You may see them (or their eggs) anywhere on a dog. However, the most common locations are on the lower back above the tail base, the groin, and the neck. 
4. Excessive licking, scratching, biting, or chewing: The sensation of the bugs crawling and biting can cause itchiness. Your dog may groom themselves excessively and chew at the fleas to remove them.
5. Hair loss (i.e., alopecia): The constant scratching and chewing can result in thinning and loss of fur. You may notice bald patches, especially in areas like the back or legs.

Fleas can also transmit tapeworms if your dog accidentally swallows an infected flea. So be on the lookout for small, rice-like segments in your dog’s feces or around their anus. If your dog has a very heavy flea infestation, the parasites can also consume enough blood to cause anemia. Signs of severe blood loss also include pale gums. This is more common in young animals. 

7 Common Signs of Dog Skin Allergies

Skin allergies have similar symptoms to flea infestations, but can also present unique signs. Here are the most common skin allergies in dogs symptoms:

1. Redness and skin irritation: Skin allergies cause inflammation, which can make the skin appear red and irritated. This is especially common in areas like the paws, belly, and armpits.
2. Excessive scratching, chewing, and licking: The itchiness causes excessive scratching and chewing. You may also notice your pet licking their paws obsessively. 
3. Hair loss (i.e., alopecia): As with fleas, skin allergies can trigger excessive dog scratching and chewing that results in loss of fur. Skin thickening may occur with skin allergies, which can contribute to hair loss.
4. Recurrent skin infections: Skin infections, both bacterial and yeast, are common in dogs with allergies. The skin barrier is often defective, allowing microscopic organisms to infiltrate. The resulting scratching and chewing can cause skin injuries that get infected. Depending on severity, skin infections may also develop a foul odor.
5. Thickening and darkening of the skin: Chronic inflammation and skin infections can cause the skin to thicken. The thickened (i.e., lichenified) skin can also take on a darker pigment. This is common in the groin and armpits of dogs with allergies. You can also see thickening of the ear canals.
6. Crusting and scaling of the skin: Allergic reactions can lead to flaky, scaly skin or crusty patches, often signaling an underlying infection.
7. Recurrent ear infections: When the skin barrier is defective, this extends into the ear canal. As such, the canal is inflamed and can easily develop an infection.

Next Steps: Itch Relief for Dogs

Regardless of what is causing your dog’s itch, consulting with a veterinarian is important for developing an appropriate treatment plan. 

Diagnosing the Cause of Itch

Determining what’s causing your dog’s itch may include the following diagnostics:

• Skin and ear cytology: Your vet may take a sample from the skin or ears and examine it under a microscope to identify if an infection is present.
• Skin scrape: Skin scraping is used to look for mites, like those that cause demodectic mange or sarcoptic mange.
• Trichograms: The veterinarian may look at individual hairs under the microscope, particularly if they’re looking for ringworm.
• Skin cultures: Your vet may perform a culture to identify what is causing an infection, especially if it doesn’t resolve with antibiotics. 
• Hypoallergenic food trials: Your veterinarian may recommend a new diet designed to avoid triggering allergies. The formula may contain a protein your dog hasn’t eaten before (known as a novel protein diet). Or, it may contain protein broken into smaller parts to prevent reactions (known as a hydrolyzed protein diet). These trials can last two months or longer and require strict control over what your pet eats. 
• Intradermal allergen testing: For this test, your dog is sedated, and potential allergens are injected beneath the skin to see if they prompt a reaction. This test is most often performed by a veterinary dermatologist.
• Biopsy: If no obvious cause is identified or your pet’s condition does not improve with treatment, a biopsy may be recommended.

Some veterinarians may recommend blood testing for allergies, but this diagnostic is not usually recommended by veterinary dermatologists. 

Treating Fleas and Skin Allergies

Treatment will depend on what your veterinarian finds with their diagnostics.

For a flea infestation:

Your vet may recommend a quick-acting flea medication like nitenpyram to kill off existing fleas, then a monthly flea preventative, like Credelio Quattro. Routine, year-round prevention is critical, especially for dogs with an allergic reaction to flea bites. Additionally, treating all pets in the household and your home environment helps prevent the spread of flea infestations.

For skin allergies:

Skin allergies often require a multi-faceted approach, depending on what’s causing the itch. To provide dog itch relief, your vet may recommend:

• Anti-itch medications like Zenrelia (ilunocitinib), which helps by reducing the inflammatory response in allergic dogs’ skin
• Medications that modulate the immune system like Atopica (cyclosporine)
• Steroids like prednisone may be used for short-term control of allergic symptoms
• Immunotherapy (i.e., allergy shots) may be an option for dogs with environmental allergies but require intradermal allergen testing
• Hydrolyzed protein or novel protein diets for dogs with food allergies
• Flea treatment and prevention, like Credelio Quattro
• Treating secondary infections with antibiotics or antifungals may also be necessary
• Shampoos that treat secondary infections or enhance the skin barrier

Dog Skin Care: How to Prevent Itchy Skin Problems

Prevention is key to keeping your dog’s skin healthy and itch-free. Here are some helpful tips:

• Use a year-round flea preventative, like Credelio Quattro.
• Stick to a balanced, hypoallergenic diet, if needed, to avoid food triggers.
• Keep your dog well-groomed and clean with regular bathing and brushing.
• Moisturize their skin using vet-approved products for dry or sensitive skin.
• Spot check dog skin for signs of fleas or allergies and act quickly to address any issues.
• Visit your veterinarian for regular wellness exams to ensure the skin is healthy.

An itchy dog is never a happy dog, but with the right care and treatment, you can help your furry friend feel comfortable again. Always consult your veterinarian to ensure you’re taking the best steps to improve your dog’s quality of life.