Canine Dermatology

Posted by  on June 15, 2010

It’s easy to forget that underneath all of that fur, your dog has skin, which in many cases is very sensitive.  Even though you can’t see most of his skin, you need to be aware of some of the problems that can affect your dog dermatologically.  In some cases, skin diseases can affect the rest of the dog, particularly the quality of his fur.

Parasitic Infections

The most common skin infection in dogs is mange, caused by an infestation of mites.  The parasitic mites burrow into the top layers of the dog’s skins, causing intense itching.  A rash may break out on the dog’s skin, and pussy nodules will form and burst, creating a crusty skin surface.  The combination of the infection and the dog’s scratching cause fur to fall out around the affected areas, and as the dog tears his skin by scratching, bacterial infections often set in.  Treatment includes oral and intravenous prescription medications and a lime-sulfur dip to help ease the dog’s misery.

Other parasitic infections include fleas, ticks, and lice.  These pesky creatures embed themselves in the skin and can cause rashes, itching, and sometimes even anemia.  You will do your dog a huge favor by giving him preventive medications each summer rather than waiting until he develops symptoms before you begin treatment.

Fungal Infections

One of the most common fungal infections is ringworm, which is really not a worm at all.  This fungus causes a ring-shaped rash that looks like a worm has curled up under the dog’s skin, giving rise to the name.  Although ringworm is not particularly harmful to the dog, it is immensely irritating to the skin, causing unremitting itchiness.  Treatment involves anti-fungal creams which are spread on the affected area.  Shaving the fur from the infected area may help heal the area more quickly.

It usually takes several weeks to clear up a ringworm infection, and care must be taken to keep human skin away from the affected area of the dog.  There are many reported cases of transfer of the infection from human to dog and vice versa.  In fact, an infected dog should not be allowed to join you in your bed, as it is highly likely you will end up with the same problem as he has.

Ringworm spores can live outside of the dog for as long as 18 months, causing repetitive infections.  Cleaners such as Benzarid are designed to kill fungal spores are available and should be used to thoroughly clean any rooms your dog regularly inhabits.

Less common fungal infections include blastomycosis and histoplasmosis.

Secondary Bacterial Infections

One of the biggest problems with parasitic and fungal infections is that they weaken the dog’s immune system, leaving him susceptible to an invasion by opportunistic bacteria.  Staph, strep, pseudomonas, and micrococcus are just a few of the bacteria that may show up on your dog during or following a parasitic or fungal infection.

Many of these bacteria can live normally on a dog’s skin without causing any problems whatsoever.  However, when the dog’s skin is broken due to an injury or a parasitic or fungal infection, and when the dog’s immune system is weakened by an infection, the bacteria can become harmful to your dog.  The infected areas of the skin may become covered in pus-filled nodules, and the dog may begin to experience more generalized signs of illness such as fever and lethargy.

Treatment can include medicated shampoos, oral antibiotics, and antibiotic sprays or creams that are put directly on the affected area of the skin.  In addition, if the infection is severe, the dog may need supportive treatments such as fluids and pain killers.

Canine Skin Allergies

Just as in humans, allergies in your dog may be manifested in his skin, with symptoms getting worse at certain times of the year.  For example, if your dog is allergic to weed pollen, you will likely see symptoms in the late summer and early fall.  Tree pollen tends to flair up in early spring, while grass pollen reaches its peak in late spring and early summer.

Although human allergies usually produce respiratory symptoms, dogs are much more likely to have dermatologic problems.  When the dog’s body encounters an allergen, it releases histamines, which make the skin begin to itch.  As the histamine level rises, the dog’s skin will be extremely itchy, causing him to lick his paws or rub his face against the carpet.  As the skin becomes raw from the dog’s attempts to relieve the itching, you may begin to see cuts or scratches in the skin, hot spots, and secondary bacterial infections.

Your dog may also have allergies to other common environmental allergens such as mold, dust, or feathers, or he may be allergic to shampoos, medications, or household chemicals.  You may be able to identify what is making him sick by the appearance of symptoms soon after changing to a new medication or chemical, but many times the source of the allergy will remain a mystery.  Your vet can do skin tests or blood tests to help identify the source of the problem, or you may choose to simply treat the allergy without knowing its exact cause.

If you can isolate one or two things to which your dog is allergic, it is best if you can remove the dog from the source of his discomfort, but that may not be possible.  For example, it is unlikely you will ever remove every speck of dust from your home, so you dog will likely still have allergic symptoms even if you use HEPA filters and are religious in your cleaning habits.

Because you cannot always remove the source of the allergens, you will need to find a way to help your dog survive his allergy season.  The first step is to treat the dog’s skin irritation so that he stops scratching.  Scratching causes the dog’s system to release even more histamines that the original allergic response did, making itching even more intense.

Your vet may prescribe an oral antihistamine medication such as Benadryl or a topical medication like hydrocortisone cream.  Fish oil in the diet may help with itching, as can colloidal oatmeal shampoos.  If the allergies continue, you may want to try a series of allergy shots which can help to reduce the histamine response when a dog encounters the substance to which he reacts.  Shots introduce a small amount of the allergen into the dog’s system so that he gets used to the substance and doesn’t release as much histamine in response to it.  Over the course of several months, the amount of allergen introduced with each shot is gradually increased.

Home Care

As you groom your dog, make sure to check for skin problems.  Any breaks in the skin should be examined for signs of infection and treated with a topical antibiotic cream.  If the area does not clear up within a week, consult your veterinarian for additional help in treating your dog.