STAPHYLOCOCCAL DERMATITIS & HYPERSENSITIVITY
What is this problem?
Staphylococcus is a name for a group of bacteria commonly found on the skin.
Dermatitis is a term that means Staphylococcal infection.
Does Staphylococci always cause dermatitis?
No. Staphylococci normally reside on the skin of animals and humans;
however, they are considered opportunists. As long as the skin is healthy, Staphylococci
are dormant. But once the skin is irritated, they can invade the area and multiply
What are likely causes of this type of skin irritation?
Scratching is the most common cause. Any disorder that causes itching can
create the situation which allows Staphylococcus to become a problem.
Common causes of itching include fleas, inhalant allergy, and food allergy.
Irritating chemicals, such as flea and tick dips, also can cause itching.
How is the condition diagnosed?
There are two typical Staphylococcal lesions. One type begins as a
red area on the skin with a pimple-like pustule in the center. The other type
is a circular, reddish area with a crusty edge and hair loss in the center.
The latter can easily be confused with ringworm. Finding either of these skin
patterns in a dog that is scratching is highly suggestive of Staphylococcal
Confirmation can be made with bacteriological cultures or skin biopsy. However,
the lesions are so typical that this is usually not necessary.
How is the condition treated?
The causal agent is a bacterium and is usually sensitive to several antibiotics.
A swab and antibiotic sensitivity test will determine the most suitable antibiotic
which usually can be administered by mouth. However, some infections may require
3-6 weeks of treatment before the infection is under control. Antibacterial
shampoos and ointments can also be helpful in bringing about rapid control of
The other essential part of treatment is stopping the itching and scratching
which may have been present before the staphylococcal infection occurred.
Other tests may be needed to determine the cause Frequently, more than one condition
contributes to the itching.
Is my dog contagious to me or other pets?
No. All dogs, cats, and people have Staphylococci living on the skin
as a normal resident.
I finished treatment for Staphylococcal dermatitis two weeks ago,
and now the infection is back. Why is that?
This situation may be caused by an allergy to the Staphylococcal bacteria.
This is called Staphylococcus hypersensitivity or Staphylococcus allergy.
The skin lesions that are caused by hypersensitivity are identical to those
of a Staphylococcal dermatitis. The difference is recurrence. If the dermatitis
is treated properly, the underlying cause Staphylococcus is eliminated
and itching stops. Thus the bacterial skin disease should be eliminated. The
situation may recur if itching returns. However, when the dog with Staphylococcal
hypersensitivity is treated, the skin lesions will return within a few days
Since differentiation of Staphylococcal dermatitis and Staphylococcal
hypersensitivity is based largely on recurrence, it is very important that
treatment be continued long enough. This often means a month or more of antibiotics.
If not, there will still be a question of which disease is present.
How is Staphylococcal hypersensitivity treated?
Treatment begins the same as for Staphylococcal dermatitis: oral antibiotics,
medicated shampooing, and whatever is necessary to stop the itching. However,
long-term control is best achieved with Staphylococcal bacterin. Staphylococcal
bacterin is a solution of killed Staphylococcal bacteria that is injected
into the dog in very tiny amounts. This is an attempt to reprogram the dog's
immune system so it does not overreact to its own bacteria. The use of Staphylococcal
bacterin begins as a series of daily injections into the layers of the skin.
After the initial series is completed, the injections are given subcutaneously
(just below the skin) on an interval of every 3-4 days to every 2 weeks. These
injections frequently will give profound improvement when other treatments have
How successful is this?
Allergy shots are never successful 100% of the time, whether in dogs or in
people. 75% of the dogs are expected to respond well.
What happens if Staphylococcal bacterin is not successful?
The dog will have to be treated periodically with oral antibiotics and medicated
baths. This is not the most desirable approach because Staphylococcus will often
develop resistance to the antibiotics. If this occurs, a change in the specific
antibiotic used will be necessary. This will also involve more bacteriological
tests and antibiotic sensitivity testing in order to establish another appropriate
course of treatment.
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