Dog Skin Allergies or Bug Bites - What Does My Pet Have?

Patrick Mahaney, VMD, CVA, CVJ
Vet Reviewed
By Patrick Mahaney, VMD, CVA, CVJ on Jun. 1, 2015
Dog Skin Allergies or Bug Bites - What Does My Pet Have?

By Patrick Mahaney, VMD

Itching (pruritus) is one of the most common reasons dogs go to see the veterinarian. There are, of course, a variety of reasons why our beloved canines chew, lick, and scratch themselves.

Why is My Dog Scratching?

Inflammation of the skin is medically referred to as dermatitis, with derma- referring to skin and -itis meaning “inflammation of.”  This will often cause intense scratching in the dog. Two of the most common types of dermatitis are allergic and parasitic. Allergic dermatitis can be caused by seasonal allergies, non-seasonal allergies, food allergies, etc. Parasitic dermatitis, on the other hand, is associated with insect bites or stings or contact with their secretions (feces, saliva, etc.).

As both allergic and parasitic dermatitis can have similarities in the clinical signs they produce, it’s crucial that you schedule a consultation and physical examination with your veterinarian so a full assessment can be performed, appropriate diagnostic testing is pursued, and the most appropriate treatment is prescribed.

How Can I Tell the Difference Between Allergies and Bug Bites/Stings?

Allergic Dermatitis

Dogs affected by allergic dermatitis may have allergies related to seasonal, non-seasonal, or food-related causes. Seasonal allergies tend to be most prevalent during spring, summer, and fall, but regions that undergo frequently warm and/or humid weather can have a year-round allergy season. Blooming plants and flowers, grasses, weeds, and trees are common contributors to seasonal allergies. Non-seasonal allergies aren’t exclusive to weather that supports plant growth and can be caused by dust, molds, environmental materials (wool, etc.), chemicals (air-fresheners, cleaning products, etc.), and other factors. While dogs most frequently suffer from allergies due to environmental triggers, allergic reactions to food are possible. Some dogs may be allergic to certain proteins (beef, dairy, chicken, etc.) and/or grains (wheat, corn, rice, etc.).

Dogs suffering from allergic dermatitis are affected all over their bodies, but most commonly on the armpits, ears, feet, groin, legs, muzzle, and around the eyes and anus. Hair loss, redness, crusting, oozing, pigment changes (hyperpigmentation), skin thickening (lichenification), and other visible signs can occur at itchy locations.

Parasitic Dermatitis

Fleas, ticks, and other biting or stinging insects can cause mild to severe inflammation and discomfort. Some dogs are extremely sensitive to the sensation of an insect bite or the allergenicity of its saliva or venom. Most often dogs will chew, lick, or scratch themselves as a result of dermatitis having an allergic or parasitic cause. Additionally, different patterns of pruritis exist depending on the location where your pet is bitten/stung, the type of insect and/or the sensitivity to the insect’s saliva or venom. Here, we will focus on fleas and ticks.

1. Fleas

Fleas commonly congregate around the head, neck, inguinal area, tail base, and perineum, which are locations where your dog will itch and scratch. Fleas jump onto pets to consume blood meals, so digested blood in the form of their feces (“flea dirt”) appearing like black pepper flakes is deposited on the skin. If you suspect your dog has flea dirt, then applying a water-moistened white cloth or tissue will melt the feces and leave behind a pink or orange-tinged residue.

Flea saliva is very allergenic, so a single flea can cause flea allergy dermatitis (FAD) that makes your dog itchy at the bite site or all over the body.

2. Ticks

Ticks are crawling parasites that move from fallen leaves, blades of grass, and other environment surfaces onto our dogs. Ticks opportunistically cling to fur when animals brush by, so the face, head, ears, and outward-facing sides of body and limbs are common places they can be found. Like fleas, ticks seek blood to survive. That is why tick bites create inflammation at the point of entry that can worsen the longer the tick stays attached and releases its saliva into the skin. Additionally, secondary bacterial infection can occur add to the tick bite site that will lead to further irritation and itching.

3. Mites

Mites like mange (Sarcoptes, Demodex, etc.) are microscopic insects that burrow deep into the layers of the skin to feed and live. Chewing their way through your dog’s skin creates inflammation and leads to secondary infections (bacteria, yeast, etc.).

Skin-lesions from mange can manifest all over the body, but the armpits, groin, ear margins, and areas having minimal hair (elbows, etc.) are most commonly affected.  Swelling, redness, hair loss, crusting, oozing, or other lesions can occur secondary to mange in dogs.


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What’s the Best Way to Prevent Dermatitis from Reoccurring?

You play a crucial role in preventing the uncomfortable sensations your dog may experience with flea and tick bites and allergic dermatitis. Fleas, ticks, and other biting insects can transmit bacteria, parasites, and viruses that can have irreversible and fatal consequences. That is why prevention is key.

Minimize your dog’s exposure by not allowing access to locations where a heavy burden of fleas and ticks may exist — wooded areas, dog parks, daycare, kennels, etc. It is also important to utilize flea and tick preventatives. As each pet’s needs differ, consult your veterinarian to determine which type of preventative is most appropriate (including topical, collar, or oral medication).

Prevention of allergic dermatitis can be somewhat complicated, due to the multiple underlying causes. Treatments may include oral, injectable, or topical medications, shampoos, conditioners, supplements (omega fatty acids, etc.), novel-ingredient and whole foods diets. Regular brushing and bathing, air filtration systems, and limiting the exposure to allergenic environments are some means by which you can also help prevent or minimize the risk your pet will suffer from allergic dermatitis.

Patrick Mahaney, VMD, CVA, CVJ
Vet Reviewed


Patrick Mahaney, VMD, CVA, CVJ


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