Allergic Dermatitis in Dogs

Overview of Canine Allergic Dermatitis

Allergic dermatitis is a general term to describe a group of skin allergies that may be caused by a multitude of factors in dogs. 

Allergies are immune reactions to a given substance (allergen), which the body recognizes as foreign. These reactions occur following initial exposure to the allergen, with subsequent development of a hypersensitivity that causes itching and inflammation upon future exposures.

The most common classes of allergic dermatitis seen in dogs are:

  • Flea bite allergy
  • Food allergy
  • Atopy – an allergic condition caused by inhaled allergens, or absorption of allergens through the skin

    Less common are:

  • Drug reactions
  • Hormonal allergies
  • Bacterial allergies
  • Allergies to other parasites (mites, intestinal worms, ticks)
  • Contact allergies (due to topical treatments or exposure to fibers, floor polish and detergents)

    Atopy and flea bite allergy are usually seen in young adults, whereas food allergy can be seen at any age. There are a number of canine breeds predisposed to the development of atopy. And some animals may be prone to development of certain allergies due to genetic factors. Allergic signs may be seasonal, depending on the cause of the allergy.

    What to Watch for

    Signs of Allergic Dermatitis in Dogs may include: 
  • Scratching, licking, chewing or biting the skin, feet and ears.
  • Red, raised, scaly areas on the skin
  • Bumps, crusts or pus filled vesicles on the skin
  • Increased skin pigmentation
  • Thickened skin
  • Loss of hair
  • Salivary staining (brown color)
  • Head shaking
  • Papular erosion dermatitis in the lower abdominal area of a dog due to food allergy.

Diagnosis of Allergic Dermatitis in Dogs

The specific diagnostic protocol may vary depending on what type of allergy or other skin disease is suspected in your dog. Every diagnostic test listed below may not need to be performed.

  • History and physical exam
  • Skin scraping
  • Skin cytology
  • Complete blood count and biochemical profile
  • Allergy blood tests
  • Intradermal allergy testing
  • Dietary trials


Treatment of Allergic Dermatitis in Dogs

The treatment prescribed by your veterinarian will vary with the type of allergy diagnosed. The following list includes the possible treatments that may be required. 

  • Avoidance of offending allergens when possible
  • Anti-itch and/or antibacterial shampoos
  • Topical anti-inflammatory or antibacterial drugs
  • Antihistamines
  • Corticosteroid therapy
  • Immunotherapy (allergy vaccines)
  • A new drug Oclacitinib (Apoquel) has been effective in some dogs
  • Fatty acid supplementation
  • Dietary management
  • Antibiotics to treat secondary bacterial skin infections


Home Care

Home care is a crucial part of treatment for any dermatologic condition. Careful adherence to your veterinarian's recommendations regarding oral medications and bathing is very important. Some animals may require bathing several times per week. Additionally, medications are often required even after the clinical signs have resolved.

Preventative Care

Although allergic dermatitis cannot be prevented, limiting exposure to allergens will help alleviate some of the clinical signs. Flea control in the environment is imperative for animals diagnosed with flea allergy dermatitis. Treating the pet alone is not sufficient to control the problem.

Environmental reduction of any known allergens is advised. This may require keeping pets inside when pollen counts are high, avoiding long grass or freshly cut grass, and limiting dust and mold in the household. Eliminating exposure to certain foods is crucial to effective treatment of food allergy dermatitis.


As discussed, there are multiple types of allergies. In addition to different classes of allergy, there are a number of other causes of dermatitis that result in the same clinical signs. The following is a list of possible diagnoses in animals with itchy, red, crusty, scaly skin.

  • Flea bite hypersensitivity- Animals with this type of allergy can have severe dermatitis even with a low flea burden. In some cases the fleas are not easily identified on the patient. This usually occurs in 3-6 year old animals. The distribution of skin lesions is predominantly on the back end of the pet.

  • Atopy- This condition is also known as allergic inhalant dermatitis. Most patients with this disorder are 1-3 years of age. There are known breed predispositions in dogs. The face, feet and armpits are the areas of the body most commonly affected by atopy. As the disease progresses, the signs may spread to the whole body.

  • Food allergy- Animals may develop an allergy to a certain component of their diet. This can occur at any age, and often occurs after an animal has been eating the diet for an extended period of time. In addition to dermatitis, some pets with food allergies will also develop vomiting and diarrhea.

  • Drug allergy- Many drugs, especially certain antibiotics, have been shown to cause allergic reactions. The signs may range from scratching and redness, to hives, to severe illness and sloughing of the skin. If a drug allergy is suspected, the drug in question should be discontinued immediately.

  • Contact allergy or irritant- Animals can be allergic to fibers in a carpet, finishes on a floor or topical shampoos or medications. Additionally, some substances may cause irritation even in animals that do not have an allergy. The dermatitis is often confined to ventral areas (along the underside of the body) or areas where there is a sparse haircoat.

  • Pyoderma- A bacterial skin infection can occur alone, or in conjunction with allergic dermatitis. Many animals develop secondary pyoderma from chewing and licking at their skin. The normal skin has many bacteria, which will colonize an area of inflamed or irritated skin and worsen the clinical signs.

  • Yeast infection- Infection with skin yeast can also occur secondary to allergy. Many patients (especially dogs) will have yeast and bacterial ear infections secondary to allergies.

  • Scabies- This is an intensely itchy disorder caused by mites. Human family members can contract this as well.

  • Cheyletiellosis- This is another type of mite that may cause minimal to severe scratching. Humans may also be infected.

  • Pediculosis- Lice infestation

Author: Dr. Erika de Papp