Canine eczema or dermatitis is an inflammation of the skin. It is not infectious to man or to other animals, but irritates the dog, making it scratch the affected part. This further inflames the skin and so the scratching/itching cycle begins.
In the acute form the dog rubs or scratches the affected part so vigorously that a weeping sore results. The surrounding hair then becomes matted with a foul smelling exudate and the area is prone to secondary bacterial infection.
In the more chronic form the skin becomes dry and thickened and the hair brittle and sparse. The areas most commonly affected are the base of the tail, the rump, and along the back. Commonly the skin between the front and hind legs becomes darkened and hairless.
In badly affected dogs virtually the whole body can be affected. In the acute form of the disease small areas can break out at the base of the ears and face. The dog can easily scratch these areas with its powerful back legs and a large area of skin can be damaged in a short time.
Certain breeds seem to be more susceptible to eczema. Corgis, Scotch terriers, pointers and golden retrievers are among those commonly treated. More importantly, the susceptibility seems to run in certain strains within a breed. Short-haired and long haired dogs seem equally susceptible.
Young dogs frequently start to scratch when shedding their puppy coat. Females coming into heat for the first time frequently develop eczema. Very old dogs also seem to be more prone to eczema in hot weather. Unfortunately, susceptible dogs that are kept indoors in centrally heated houses can suffer from eczema at any time of the year.
As with human dermatitis, the causes of canine eczema are varied, and not fully understood. Infestations of fleas certainly play a major role in most eczemas. The flea is a blood sucker and the irritation from flea bites can start the itching/scratching cycle on its own. Unfortunately many dogs become hypersensitive to the protein in the saliva of the flea so that the irritation caused by just a single flea bite can be considerable.
Allergies from other sources have been incriminated. Some dogs develop a contact dermatitis along the under surface of their body from certain grass pollens in the spring. Other dogs can develop acute allergic wheals in the skin from eating pork or fish or certain spices in sausages. Some chemicals in soaps or shampoos can produce an acute eczema, and some dogs cannot tolerate a flea collar.
Veterinarians are always asked about diet and its effect on eczema. Apart from the straight out allergies discussed above we know of no specific dietary factor which is responsible for eczema. On the other hand, we have not isolated any factor where deficiency causes eczema except in extreme cases of malnutrition and absence of vitamins A and C.
There is currently a popular belief that the addition of zinc and vitamin E will help cure eczema. Certainly some cases have responded but the position is far from clear. Similarly, the deficiency of the thyroid hormone is responsible for chronic eczemas and hair loss in some animals.
It can be seen from all this that there can be no one cure for eczema. Each case must be carefully evaluated by the veterinarian before treatment is begun. Quite often drastic treatments can further insult the skin and inhibit the normal repair processes.
In acute eczema the veterinarian frequently prescribes drugs which have an anti-inflammatory effect on the damaged and itchy skin. These are usually given by injection at first and followed with a course of tablets. Ointments to soothe the skin locally and prevent secondary infection of the damaged tissues are used but are not sufficient treatment in themselves.
It is vital to prevent flea infestations. Washes of a safe insecticide such as Malathion are usually more efficient than soaps or powders. Flea collars are useful in preventing re-infestation once the dog is freed of fleas. Do not use flea collars and an insecticide wash at the same time. Avoid washing the dog with strong disinfectants or soaps. Use only a neutral soap or shampoo suitable for babies. Too much washing dries out the skin and makes it further susceptible to eczema.