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Dog skin disorders are among the most common health problems in dogs. Skin disorders in dogs have many causes, and many of the common skin disorders that afflict people have a counterpart in dogs. The condition of dog's skin and coat can also be an important indicator of its general health. Skin disorders of dogs vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. Dog skin disorders may be grouped into categories according to the causes.

Contents

Types of disorder

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Immune-mediated skin disorders

Skin disease may result from deficiencies in immune system function. Some examples include increased susceptibility to demodectic mange, recurrent skin infections, such as Malassezia infection or bacterial infections. This category also includes hypersensitivity disorders such as atopic dermatitis, and skin diseases caused by autoimmunity, such as pemphigus and discoid lupus erythematosus.

Canine Atopic Dermatitis

Canine atopy 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 on the 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.

Canine Atopy with dermatitis around the eye created by rubbing

Ear and skin infections with Staphylococci and Malassezia (yeast) are common secondary to canine AD. Some of the allergens associated with canine AD include pollens of trees, grasses and weeds, as well as molds and House dust mite. Food allergy can be associated with identical signs and some authorities consider food allergy to be a type of atopic dermatitis. Flea allergy is commonly associated with AD. AD is a life-long condition in most dogs.

Diagnosis of AD is by elimination of other causes of irritation including fleas, scabies and other parasites such as Cheyletiella and lice. Food allergy can be identified through the use of elimination diet trials in which a novel diet is used for a minimum of 6 weeks and allergies to aeroallergens can be identified using intradermal allergy testing and/or blood testing (allergen-specific IgE ELISA).

Treatment for AD includes avoidance of the offending allergens if possible, but for most dogs this is not practical. 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 and ear cleaners may be needed to try to prevent the return of infections.

Hot Spots

A Hot Spot, or acute moist dermatitis, 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 Staphylococcus 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.

Acral lick granulomas

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. According to the Merks Manual of Veterinary Medicine, compulsive licking has the following necessary condition: licking in excess of that required for standard grooming or exploration. The following condition is sufficient: licking in excess of that required for grooming or exploration that represents a change in the animal’s typical behavior and interferes with other activities or functions (eg, eating, drinking, playing, interacting with people) and cannot easily be interrupted.[1]

Infectious skin diseases

A dog with skin irritation and hair loss on its leg caused by demodectic mange

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

One of the most common contagious parasitic skin diseases is Sarcoptic canine scabies. Another is mange caused by Demodex (Demodicosis), though this form of mange is not contagious. Another contagious infestation is caused by a mite, Cheyletiella. Dogs can be infested with contagious lice.

Other ectoparasites, including flea and tick infestations are not considered directly contagious but are acquired from an environment where other infested hosts have established the parasite's life cycle.

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

Dog with dermatitis caused by Malassezia (yeast)

Non-contagious skin infections can result when normal bacterial or fungal skin flora is allowed to proliferate and cause skin disease. Common examples in dogs include Staphylococcus intermedius pyoderma, and Malassezia dermatitis caused by overgrowth of Malassezia pachydermatis.

Flea allergy dermatitis

See Flea allergy dermatitis

Hereditary and developmental skin diseases

Some diseases are inherent abnormalities of skin structure or function. These include seborrheic dermatitis, ichthyosis, skin fragility syndrome (Ehlers-Danlos), hereditary canine follicular dysplasia and hypotrichosis, such as color dilution alopecia.

Cutaneous manifestations of internal diseases

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

References

  • Medleau, Linda; Keith A Hnilica (2006). Small Animal Dermatology A Color Atlas and Therapeutic Guide. St. Louis, Missouri: Saunders Elsevier. ISBN 0-7216-2825-7.  
  • Scott, Danny W.; William H. Miller, Jr; Craig E Griffin (2001). Muller & Kirk's Small Animal Dermatology 6th Edition. Philadelphia, PA: WB Saunders Company. ISBN 0-7216-7618-9.  

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