ALLERGIC SKIN DISEASE
Allergic skin disease is one of the most common and most frustrating
problems we see as vets. It can affect any animal at any age,
although certain breeds are more pre-disposed to allergies than
others. Common skin allergies in dogs (and cats) include:
1) Flea Allergic Dermatitis – allergy to flea’s saliva, so even one
bite can cause a reaction.
2) Atopy – allergy to breathed in allergens like pollens and dusts.
3) Contact allergies – allergies to allergens the animals physically
come into contact with e.g. grass allergy.
4) Food allergies – allergens in food can cause a skin reaction.
Allergies cause inflammation (redness, heat, etc) in the skin and
pruritus (itchiness) which leads to the itch/ scratch cycle where the
animal makes the problem worse by scratching or biting the skin.
This then leads to secondary problems such as bacterial or yeast
overgrowths on the skin, again making the problem worse.
DIAGNOSING ALLERGIC SKIN PROBLEMS
The symptoms of skin allergies are fairly typical, however, gaining a
specific diagnosis (i.e. is it food or grass?) can be very difficult. The
only way to truly get a diagnosis is by performing blood or skin tests
(as is done in humans) to try to isolate specific allergies. Often,
animals are allergic to more than one allergen.
Exclusion trials can also help to diagnose allergies but are more
difficult to perform. For example, if you think it’s flea allergic
dermatitis, treat vigorously for fleas and see if the allergy resolves, or
if you think its food, use a hypoallergenic diet for 2 months and see if
it helps.
TREATING ALLERGIC SKIN DISEASE
The first important concept to understand is that allergies cannot be
cured. (If they could, no one would suffer from hay fever any more!)
Therefore, we need to look more at managing or preventing allergic
skin problems in the long term.
Short term treatment - addressing secondary problems such as
bacterial or yeast overgrowth can be done using antibiotics,
antifungals, or shampoos. It is essential to stop the existing itch/
scratch cycle by resolving inflammation and pruritus. This is usually
done using drugs such as Prednisolone (Cortisone, Steroids),
Antihistamines, or Cyclosporine (Atopica). These drugs can have
negative side effects if used in the long term, however, they are
essential to control short term inflammation and pruritus. They can
safely be used in the short term if prescription guidelines are
followed.
Long term treatment - if blood tests are performed and specific
allergies are identified there is often the possibility of manufacturing a
vaccine to desensitize the animal against the cause of the allergy.
This involves a series of regular injections over about a year, and
then maintenance of life long vaccinations.
Some animals do not respond to any of the other treatment or
management measures and due to the affect of the allergy on their
well being and comfort, require long term treatment with Prednisolone
or Cyclosporine. This is NOT IDEAL, and is a last resort, but
sometimes becomes the only option other than euthanasia. In these
cases, specific recommendations need to be followed to reduce side
effects, and regular check ups (sometimes including blood tests) are
required to monitor the effect of the drugs on the animal.
MANAGING SKIN DISEASE
1) Fleas - every dog or cat with a skin disease should be treated
regularly (i.e. monthly) for fleas. Even if they don’t seem to have
fleas, or if flea allergic dermatitis is not their primary problem, every
flea bite will make matters worse.
2) Shampoo - bathing helps to reduce bacterial and yeast populations
in the skin, as well as removing dirt, oil and old skin and hair. The
frequency depends on the coat type and problem (typically every 2-4
weeks). The type of shampoo is very important and depends on the
problem – anti-bacterial, anti-fungal, and conditioning shampoos are
all available; for example, Malaseb for yeast and bacteria, Pyohex for
bacteria, Aloveen for inflammation alone.
3) Food - food allergy is a specific diagnosis, however, a
hypoallergenic diet can benefit any animal with skin disease. The
easiest way to apply this is to use a prescription diet (eg eukanuba
response FP or Hills Z/D). However, home cooked diets can be
created using basic principles. Usually, the basis is a “novel protein”
(i.e. a meat that the animal has not eaten before such as kangaroo,
rabbit, fish, turkey etc.) and a carbohydrate source other than wheat
(rice, potatoes, corn etc.) This has to be strictly controlled and will
take 6-8 weeks to show effect.
4) Supplements - Omega 3 and 6 essential fatty acids (oils) can be
added to the animals diet and greatly assist in maintaining a healthy
skin. Examples are: evening primrose oil, flaxseed oil and cod liver
oil, or a combination of these oils.
5) Avoiding allergens - this again depends on the specific problem,
and can be difficult to do. Try to avoid long grass, creeping plants
(e.g. wandering dew and ivy), dusty environments, water with algae,
home improvements (dust, paint, chemicals, fumes etc.), and keep
bedding and kennels clean and dry.
6) Grooming - keeping the animal’s coat short and in good condition
can help a lot, especially in the summer months. Clipping and
brushing out old hair is vital to keep the coat healthy.
IN SUMMARY:
Allergic skin problems will not go away, they may be seasonal (worse
in summer for instance), but it is very rare to achieve a cure to allergic
skin disease. Therefore, constant management measures are
required to keep the symptoms under control. If all measures have
been exhausted and the animal’s welfare is still affected by constant
irritation, immunosuppressive drugs can be used, but long term use
may cause side effects which can be catastrophic. Diseases such as
Diabetes, Pancreatitis, liver disease and Cushing’s disease can all be
caused by long term steroid usage. Veterinary Dermatologists
(specialists) are available for a second opinion or for difficult cases.