There are a multitude of causes of pruritus
(itching) in dogs and it is impossible to cover all of these in one article,
where pruritus is the presenting symptom this condition can be broadly be
divided into two categories, one is parasitic and the other is allergic
dermatitis.
Today I shall be dealing primarily with the
main cause of allergic dermatitis, which is atopic dermatitis.
The cause of this is allergens in the
environment, microscopic molecules that translocate across the skin and result
in histamine release mainly by mast cells in the sub-epidermal tissues. This
histamine release causes pruritus, therefore the dog scratches itself; this
then breaks the skin barrier and damages the skin’s protectant layers allowing
bacteria, usually staphyloccos aureus, to cause a secondary skin infection.
These skin infections are often seen as concentric rings and are often confused
with ringworm( a fungal infection). This
secondary skin infection in itself also causes inflammation and more pruritus,
this causes more itching etc and therefore a cascade effect is set off.
When neglected and treatment is not sought
promptly enough the problem can escalate, with further yeast infection and
often more pathogenic bacteria invading the affected areas. At this point the
dog has a particularly pungent odour and you are looking at a long protracted
course of treatment to bring the condition under control.
The equivalent in humans to atopy in dogs,
again broadly speaking, is asthma. Due to the different distribution of mast
cells in dogs these develop skin problems as opposed to coughing and
respiratory problems. In the cat on the other hand feline asthma is
particularly common, but that is a topic I will leave for another day.
The areas of principally affected by atopy
in dogs are those with poor coat cover and often areas of increased movement,
and it generally first presents when the dog is over a year of age. Most classical sites affected are the groin,
axilla, ventral areas, feet and ears. If your dog has recurrent skin problems
in the afore mentioned regions then you are more likely than not dealing with
an atopic dermatitis and therefore treatment must be tailored at this.
Another pattern you might notice is you
might find that the condition is seasonal; again this can often be correlated
very closely with people who suffer from asthma. For example if the flare up is
in spring then it is likely to be caused by the increase in pollen in the
atmosphere. If the flare up is in colder periods when these allergens are
markedly reduced then the condition is most likely to be caused by house
allergens, the main culprits being house dust mites. In the winter dogs will
seek more warmth and blankets are a great habour for these mites. Keeping the
bedding clean is not sufficient, washes have to be at high temperatures to kill
the mites otherwise all you are doing is giving the mites a shampoo and blow
dry and putting them back.
Treatment is a relatively simple affair but
it will be a minimum of three weeks of aggressive therapy, usually when the dog
is presented for treatment the skin is already infected, and skin infections
need an obligatory period of three weeks of antibiotics and adjunct medicines,
shampoos etc. One of the main shortfalls of treatment is not giving the animals
medication for long enough, therefore the problem recurs rapidly and the
clients become disenchanted.
The biggest challenge once the condition is
diagnosed is trying to control the illness long term with prophylactic therapy.
There are a multitude of options available, there is no specific treatment plan
to treat all dogs, and it has to be tailored to each individual case. This
varies with the severity of the problem and the response to treatment by each
individual animal, so sometimes patience is a virtue.
In summary if your dog has recurrent skin
complaints with itching, usually affecting the same regions then your pet is
probably suffering from atopic dermatitis and the earlier it is treated the better and the easier it is to manage the problem.
