Skin disorders in dogs

Dog skin problems, conditions and disorders are a common health issue addressed by our veterinarians.

Your dog's skin is their body's largest organ and is reflective of your dog's overall health, both mental and physical, and can be affected by inside as well as outside sources.

Skin disorders in dogs have many causes, and vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. They also need to be differentiated on the basis of being of primary or secondary (due to scratching) in nature, making diagnosis complicated.

Dog skin disorders may be grouped into categories according to the causes.

  • Immune-mediated skin disorders
  • Physical and environmental skin diseases
  • Infectious skin diseases
  • Flea allergy dermatitis
  • Hereditary and developmental skin disease
  • Cutaneous manifestations of internal diseases

Immune-mediated skin disorders

Skin disease may result from deficiency or over-activity of immune responses.

In cases where there is insufficient immune responses the disease is usually described by the secondary disease that results. Examples include increased susceptibility to mange and recurrent fungal or bacterial skin infections.

Increased, but harmful, immune responses can be divided into hypersensitivity disorders such as atopic dermatitis, and autoimmune disorders such as pemphigus.

Canine Atopic Dermatitis

Atopic dermatitis is a hereditary and chronic allergic skin disease. It usually starts between 6 months and 3 years of age with some breeds of dog such as the Golden Retriever starting at an earlier age. Dogs with AD are itchy, especially around the eyes, muzzle, ears and feet. In severe cases the irritation is generalised. In cases where the allergens are seasonal the clinical signs of irritation are similarly seasonal, but many dogs with house dust mite allergy have perennial disease.

Some of the allergens associated with canine AD include pollens of trees, grasses and weeds, as well as molds and house dust mites. Bacterial ear and skin infections are common secondary problems for dogs with AD. Flea allergy is commonly associated with AD. AD is a lifelong condition in most dogs.

Diagnosis of AD is by elimination of other causes of irritation including fleas, scabies and other parasites such as lice. Food allergy can be identified through the use of elimination diet trials.

Treatment for AD includes avoidance of the offending allergens if possible, but for most dogs this is not practical or effective. Other treatments modulate the adverse immune response to allergens and include antihistamines, steroids, ciclosporin and immunotherapy (a process in which allergens are injected to try to induce tolerance). In many cases shampoos, medicated wipes and ear cleaners are needed to try to prevent the return of infections.

Research continues into T-cell receptor peptides and their effects on dogs with severe, advanced atopic dermatitis.

Autoimmune skin diseases

Pemphigus foliaceus is the most common autoimmune disease of the dog. Blisters in the epidermis rapidly break to form crusts and erosions most often affecting the face and ears initially, but in some cases spreading to include the whole body. The paw pads can be affected causing marked hyperkeratosis (thickening of the pads with scale).

Treatment of autoimmune skin conditions requires treatment to markedly reduce the abnormal immune response; steroids, azathioprine and other drugs are used as immunosuppressive agents.

Physical and environmental skin diseases

Hot Spots

A Hot Spot, is an acutely inflamed and infected area of skin irritation created and made worse by a dog licking and biting at itself. A hot spot can manifest and spread rapidly in a matter of hours as secondary staph infection causes the top layers of the skin to break down and as pus becomes trapped in the hair. Hot spots can be treated with corticosteroid medications and oral as well as topical antibiotic application, as well as clipping hair from around the lesion. Underlying inciting causes include flea allergy dermatitis, ear disease or other allergic skin diseases. Dogs with thick undercoat are most subject to getting hot spots.

Related to Hot Spots are Lick granulomas, a raised, usually ulcerated area on a dog's wrist or ankle area caused by the dog's own incessant compulsive licking.

Infectious skin diseases

Infectious skin diseases of dogs include contagious and non-contagious infections or infestations. Contagious infections include parasitic, bacterial, fungal and viral skin diseases.

Canine scabies, mange, mites and lice all fall within this category, along with flea and tick infestations.

Ringworm is a fungal skin infection and is more common in puppies than in adult dogs.

Non-contagious skin infections can result when normal bacterial or fungal skin flora is allowed to proliferate and cause skin disease.

Flea allergy dermatitis

Flea allergy dermatitis is an eczematous itchy skin disease of dogs and is the most common cause of skin disease. Affected dogs develop allergic reactions to chemicals in flea saliva. Symptoms of this reaction include redness, bumps, pustules, scabs and if severe, hair loss will occur in the affected area. Dogs with flea allergy dermatitis often show hair loss and eczematous skin rash on the lower back, upper tail, neck and down the back of the legs.

Hereditary and developmental skin diseases

Some diseases are inherent abnormalities of skin structure or function.

Cutaneous manifestations of internal diseases

Some systemic diseases can become symptomatic as a skin disorder. These include many hormonal abnormalities, such as hypothyroidism, Cushing's Syndrome and tumours of the ovaries or testicles.

What to do?

If your dog is experiencing an extended bout of itchiness and scratching to the point of damaging his skin, take him to the vet for a proper diagnosis.

With a little bit of detective work, itchiness can be successfully managed. You will then have a much healthier, happier, and relaxed companion.