SPCA New Zealand
Advice & welfare

Common skin problems in dogs

There are hundreds of different diseases that affect the skin of dogs. Since the skin can only react in a limited number of ways many of these diseases look very similar, which can make skin disease difficult to diagnose accurately.

If your dog has a skin problem, it is important to see your veterinarian to help determine the kind of skin problem and the appropriate treatment. Sometimes it will be necessary to see a veterinarian who specialises in skin (a veterinary dermatologist) for problems that are hard to diagnose or treat.

Discussing all skin problems found in dogs would fill many books, so we’re going to concentrate on the problems most commonly seen in this article!

Atopic dermatitis

Also called atopy, this is a very complex and multifactorial disease that involves:

  • An allergic reaction to environmental allergens (such as grass, weed/tree pollens, moulds, dust mites or insects); this is similar to hayfever and atopic eczema in people.
  • Abnormal skin that does not function normally as a barrier and so allows increased penetration of allergens and infections; this leads to stimulation of the immune system.
  • Secondary infections, usually with bacteria and yeast.

Genetics play important role in atopic dermatitis and some breeds seem predisposed, these include Beagles, German Shepherds, Labrador, Staffordshire Bull Terriers and West Highland White Terriers.

Factors that would indicate that your dog might have atopic dermatitis include:

  • The signs of skin disease started early in your dog’s life (<4 years old).
  • Your dog is itchy, this may be the only sign initially. The itch is likely to be affecting the feet, face, ears, around the eyes, abdomen, groin and/or bottom. The itching often results in your dog causing some trauma to their skin, this results in some or all of the following: hair loss, red inflamed skin, erosions, crusting, thickening, scaling, hyperpigmentation (darkened skin) and malodourous greasy skin.
  • The itch improves if your dog is given corticosteroids.
  • Your dog gets recurrent skin or ear infections; these may be bacterial, fungal or yeast.
  • Your dog is a purebred or a cross of one of the breeds that are commonly affected by atopic dermatitis.

The diagnosis of atopic dermatitis is based on the presence of some or all of the above signs, the clinical elimination of other diseases that could cause similar signs and response to medication.

As atopic dermatitis has three main components that contribute to the disease, all three must be treated:

  1. The allergic component of the disease is best treated with immunotherapy and desensitisation. This involves intradermal allergy testing to identify the allergens involved and the creation of a special allergy vaccine specific to your dog’s allergies. If immunotherapy is ineffective, not possible or not desired, the allergic component of the disease needs to be controlled with some form of anti -inflammatory medication. There are a number of different medications available, your veterinarian can advise you on the one that is most appropriate for your dog.
  2. Improving the barrier function of the skin can be achieved by using some of the following: essential fatty acid (Omega 3 & 6 essential fatty acid oils) oral supplements, a special veterinary skin support diet and special shampoos and conditioners that help improve the skin’s hydration and provide short-term relief of irritation.
  3. Secondary bacterial and yeast infections need to be controlled. The type of organism causing the infection will need to be identified through cytology and the most appropriate drug used based on those results. This may involve oral drugs such as antibiotics and/or medicated shampoos, residual antiseptic conditioners, anti-fungal creams/lotions and medicated rinses.
It can be challenging to control atopic dermatitis but it is a disease that significantly impacts the quality of life of your dog. Therefore, it is very important to have the disease properly diagnosed and treated so that your dog can live a happy life without the discomfort and serious side-effects of the disease.

Flea allergic dermatitis

When a flea feeds on your dog’s blood it injects saliva into the skin. In some dogs, repeated exposure to flea saliva can cause them to develop an allergic reaction to the flea’s saliva; this results in an inflammatory response, causing severe itching and self-trauma. The areas most commonly affected are around the base of the tail, along the back and the back of the thighs. It is important to note that, once the allergy has developed, the inflammatory response can be triggered by only a tiny amount of flea saliva. Often there are very few or no live fleas present on an animal that has flea allergic dermatitis.

Unfortunately, once the allergy has developed, there is no cure but the allergy can be controlled. Initially the dog is likely to need some anti-inflammatory medication to relieve the symptoms, as well as an effective flea treatment. Control of flea allergic dermatitis involves elimination of fleas from your dog and their environment. Thankfully there are now some very effective products available to achieve flea control. It is best to talk to your veterinarian about the most up to date and effective flea control options.

Otitis externa

Otitis is a general term that means inflammation of the ears. In otitis externa the inflammation affects just the outer part of the ear (the ear canal and often the ear flap). This is a very complex disease potentially involving many different underlying factors and it is important to identify these in order to effectively control the disease.

The most common reason that a dog is presented for treatment of ear disease is because a bacterial or yeast infection has developed. However, infections are hardly ever the primary ear disease process; instead the infection is usually secondary to inflammation of the ear. Examples of primary disease processes that can cause ear inflammation are: allergies (a very common cause), parasites, keratinisation disorders and autoimmune diseases. In addition, there are many conditions that can predispose a dog to develop ear inflammation, for example: ear conformation problems (hairy, narrow or pendulous ears), excessive moisture (often from swimming), obstructions of the ear canal (e.g. a polyp or tumour) and systemic illness.

The clinical signs shown by the affected dog will depend on both the underlying disease that is triggering the inflammation and on any infection that has subsequently developed. The affected ear is often red and swollen, there may be discharge in the ears (this may be yellow or red coloured and/or dark brownish red tinged) and crusting. The dog is normally shaking their head, scratching at the affected ear and may find it painful to have the ear touched.

The diagnostic investigation of otitis externa should involve two separate but important and interconnected components:

  • If an infection is present, it will be preventing resolution of the ear inflammation. Therefore, the organisms (bacteria or yeast) that have proliferated must be identified. To do this your veterinarian will need to collect a sample from the ear and examine it under a microscope. It is also often necessary to collect samples and submit these for culture and sensitivity testing to select the most appropriate therapy for the organism (as the bacteria involved may be resistant to some antibiotics).
  • The primary cause of the inflammation must be investigated and identified. If this is not done then the ear inflammation and secondary infections are likely to continue to recur and long-term resolution is difficult. Your veterinarian will need to perform a thorough examination of the ear and down the ear canal with an instrument called an otoscope. This process allows your veterinarian to check that the ear drum is intact (this is important to establish prior to giving ear drops as some of them are toxic to the inner ear and can cause problems if the ear drum is perforated and allows the ear drops to enter the inner ear) and allows the identification of physical factors in the ear that may be involved in the problem such as foreign bodies (e.g. grass seeds), polyps or tumours. It may be necessary to sedate or aneasthetise the dog to perform this thorough examination of the ear canal, particularly if the dog is in a lot of pain. Other diagnostic tests may also be necessary to investigate possible underlying causes such as allergies.

In order to successfully resolve otitis externa both the infection (if present) and the underlying disease process must be treated effectively.

Effective treatment often involves some or all of the following:

  • If there is a significant amount of debris and discharge in the ear canal this must be removed, as it prevents penetration of any eardrops, can inactivate antibiotics and increases the inflammatory response. Cleaning out the ear canal may necessitate sedation or aneasthesia if the dog is in a lot of pain, there is significant inflammation and/or there is a lot of debris and discharge in the ear canal.
  • Oral and topical medication will then most likely need to be prescribed to reduce inflammation and eliminate the infection. The choice of medication is usually based on examination of the ear sample, and the culture and sensitivity results.
  • If an underlying cause such as an allergy is identified it must also be treated so that the infection does not continue to recur.

Demodectic mange is a parasitic infestation caused by demodex mites and is a relatively common skin problem, particularly in young dogs.

Demodectic mange

These mites are found on nearly all dogs and live inside the hair follicles. The mites are a normal part of the skin but in some dogs there is a problem that allows the mites to proliferate abnormally and cause disease. The demodex mites are species specific and so there is no danger of humans becoming infected.

There are three different kinds of disease syndrome caused by demodex mites:

  • Localised disease in which the excessive mite proliferation is restricted to a few small areas (<6 in total). Localised demodectic mange is characterised by patches of hair loss with the skin underneath becoming crusty, itchy, red and/or moist. This form of demodectic mange most commonly occurs around a dog's front legs, eyes, muzzle and other parts of the head. In most cases, localised demodectic mange will resolve itself and treatment is not required. However, treatment will often speed the resolution of the mange.
  • Generalised disease in which the excessive mite proliferation involves larger numbers of lesions and in various body regions; in severe cases it can spread across a dog’s entire body. This is a much more serious condition than the localised form and immediate and aggressive treatment is needed. Dogs with generalised disease commonly develop a secondary bacterial infection, which can be very serious. There is a lot of variation in the clinical signs seen with generalised disease but these can include: hair loss, pustules (like little pimples), papules (little lumps in the skin), crusts, hyperpigmentation (darker colouration of the skin) and swelling (most commonly of the feet).

Generalised demodectic mange is divided into juvenile and adult onset disease; these each have different causes and prognosis:

  • Dogs that have juvenile onset demodectic mange generally have an inherited abnormality of their immune system that means they are unable to control the mites and stop them proliferating abnormally.
  • Dogs that have adult onset demodectic mange generally have a concurrent underlying disease that is suppressing their immune system. This is a more worrying form of the disease as it is often indicative of serious underlying disease that must be identified and treated.

It is possible that the affected area may develop a bacterial infection with any form of demodectic manage, although it is unusual in the localised form. If an infection is present pustules, papules and crusts may affect the skin. If a dog is suspected to have demodectic mange they should be taken to see a veterinarian as soon as possible. Localised demodectic mange may resolve itself without requiring treatment but veterinary attention is still recommended.

Diagnosis of demodectic manage usually straight forward. The veterinarian will need to take a deep skin scraping from the affected area; the sample obtained is examined under a microscope to identify the mites. It is very important that animals with adult onset disease have a thorough investigation to identify the underlying cause of the immunosuppression that is allowing the mites to proliferate.

Once the diagnosis is confirmed, treatment will be discussed. This will depend on the individual case but, if necessary, may involve systemic (injections or oral medication) or topical (e.g. an insecticidal dip) medication. Treating generalised demodectic mange can be an involved process and can take some time. Dogs with adult onset generalised demodectic mange will need their underlying disease identified and, if possible, treated. Dogs that have secondary bacterial or fungal skin infections will also need injectable, oral or topical antibiotics, oral or topical anti-fungal medications and/or special medicated washes as appropriate to the individual.

Regular skin scrapings to look for the mites need to be taken throughout the treatment process. This will normally be performed after 4 weeks and then every 2 weeks. Two negative scrapings in a row will indicate that the mange has been resolved and the treatment can stop.

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