Skin Diseases

By | June 21, 2010

Diseases Of Different Organs

Alopecia

This skin condition shows as complete loss of hair right down to the hair follicles and is the equivalent of human baldness. Hair will not grow again where the follicles have become completely inactive, unlike ordinary hair- shedding where the hair breaks off but the follicles produce new hairs. Odd patches of alopecia, particularly in ageing dogs, are not a cause for anxiety, but extensive areas of complete hair loss are frequently associated with hormonal disturbances and indicate the need for veterinary examination. Extensive patches arranged symmetrically across the body could be an indication of thyroid of adrenal gland disturbance, or in males a tumour of the testis.

Acne

This skin condition of human puberty does not occur in dogs, but similar small abscesses are occasionally found around the mouth of a dog of any age. They are usually the result of the dog’s exploration of deep cover, an encounter with a hedgehog or similar obstruction. Treatment is as for other abscesses, and care must be taken to ensure that no thorns or spines remain. Delayed healing or suspected infection under the skin (furunculosis), especially in Spaniels, need professional attention.

Abscess

This is the equivalent of a boil or carbuncle, and usually the result of micro organisms being introduced into or under the skin. Bacteria that normally live in the skin may proliferate in favourable circumstances. Abscesses in the gut or liver are difficult to detect, although the effects may make the dog very ill. Professional help is needed for a proper diagnosis. An abscess produces swelling, inflammation and local heat, and the contents become a thick liquid or semi-liquid, foul-smelling, often blood-stained mass.

Bite wounds often produce abscesses as the teeth can introduce infected material through only a small tear of the skin. With little aeration of the wound, bacteria rapidly proliferate. Bite wounds can be difficult to locate in dark- skinned, long-haired dogs and it is not always easy to distinguish between the bite wound and the site of the abscess.

Pus may track in any direction and emerge elsewhere as a fistula, or channel between the surface and another site, often a cavity such as the rectum, anal sac, or vagina. Fistulae may also form between internal structures, where their presence is difficult to detect, or they may emerge through the skin round the mouth or, more commonly, the anus, particularly in German Shepherd Dogs. Extensive surgical correction is often necessary.

An abscess may form at the root of a tooth, with pus being unable to drain away if the abscess is in the upper jaw. A weeping eruption may be present just below the eye and can easily be mistaken for an eye condition; as pus must drain downwards, the offending tooth may have to be removed.

Abscesses are treated by cleaning the area, particularly fight wounds, and removing hair, pus, and soil, grit or oil, which can contaminate the area. The dog’s natural defenses can be aided with local heat applied as lint soaked in hot water. This should be repeated every two to three hours during the day, and as soon as the abscess has come to a point, every effort should be made to evacuate the pus, which must be allowed to drain downwards. Failing this, the abscess must be lanced by a veterinary surgeon.

Cleaning of the area and local heat should be continued after an abscess has erupted as the exit quickly closes over, trapping any pus left inside the abscess. Any persistent or obviously painful swelling needs veterinary attention as it may contain a grass awn or piece of fish hook.

Dermatitis

The term describes simple inflammation of the skin and allied structures; with a proliferation of bacteria it becomes infective dermatitis. Parasitism, allergy, contact with irritants, food intolerance or deficiency, heat stroke, and a large number of other conditions may lead to dermatitis.
Skin problems are usually obvious. They take a long time to investigate and to clear up as restorative changes are slow, and diagnosis of the problem can be difficult and prolonged.

Demodectic mange

chiefly occurs in dogs under one year old, although the skin changes may persist for years or be permanent if hair follicles are destroyed.

Hyperkeratosis

Infectious disease, such as the hardpad manifestation of canine distemper, can show as a thickening of the surface of the skin, hyperkeratosis. Thickening also occurs around the nose and occasionally corn-like swellings appear at the points of the elbows, where bones are near the surface of the skin. Excessive flaking of the skin, with drandruff or scurf over the entire body, may be related to marginal zinc intake, particularly when cereal food makes up a disproportionate part of the diet. Improved diet, frequent bathing and possibly zinc supplementation usually resolve the condition.

Lick Granuloma

This term describes chronically inflamed skin which eventually ulcerates, on the foreleg usually just above the toes. It is frequently seen in Labradors, though not confined to that breed, and in other short-haired dogs, active by nature and left to feel bored. The likely cause is a minor skin injury which is gradually opened up by the dog by continuous licking. The area becomes itchy and is not given a chance to heal. Efforts should be made to prevent the dog from licking the granuloma, but the irritation remains for quite a time. Bandaging will not always deter a determined dog, but an Elizabethan-collar arrangement is usually effective if cumbersome. Persistent or extensive granulomas are best removed by cryosurgery, a technique in which the tissues are frozen, using a special probe.

Nettle Rash

A sudden allergic reaction, urticaria, may show in the appearance of the skin. The first sign is usually a swelling of the eyelids, which may progress to a puffy enlargement of the whole head and neck. Blisters may appear, and the skin may look pitted. Sometimes the skin can be lifted or a depression made in it which remains unchanged for a long time. Urticarial or Nettle Rash reaction may follow inhalation or ingestion of any substance to which the dog has become sensitized; it can also follow an insect sting. In many cases the allergic reaction recedes as quickly as it appears. In others it may persist, and occasionally it interferes with breathing or heart function. All but the most transient reactions need expert advice.

Seborrhoea

A dog’s skin produces a wax-like, greasy secretion which lubricates the coat. An overproduction of the sebum produced by the sebaceous glands, or an accumulation of waxy secretions in association with scaliness of the skin, leads to seborrhoea. Skin and coat appear greasy, dull and scurfy and have a characteristic mouse-like smell. Some Terriers are commonly affected but seborrhoea is most frequently seen in Cocker Spaniels, probably due to hormonal disturbance. The best treatment is anti-sebum shampoos.

Ringworm

Two types of fungal infection may grow on dogs’ hair and skin, causing ringworm. They have nothing to do with worms, are not usually circular and are not at all common in dogs. More than half of the cases seen are caused by a fungus, Microsporium spp., which is more at home on cats and which fluoresces under ultraviolet light. Other species of ringworm fungus need more complex tests to establish a diagnosis. Treatment is usually effective if slow. Fungicidal drugs by mouth and topical applications diligently applied eventually bring results as the hairs are broken off, not usually destroyed. The risk of passing canine ringworm to humans is minimal if a reasonable standard of hygiene is maintained. The condition affects debilitated individuals; nutrition should be improved.

Self – Inflicted Skin Problem (Lick Granuloma)

Lick granuloma is the descriptive term for an area of chronic skin ulceration which results from incessant licking by a cat’s or dog’s own tongue. The word granuloma refers to zones of tissue which are undergoing persistent inflammation with subsequent thickening and fibrosis. Lick granulomas are not uncommon in dogs in Britain and in the USA the same condition is often called acral lick dermatitis or pruritic nodule, In a typical lick granuloma, the ulcerated area of skin over the forepaw is clean, pink, flat and moist and can freely be moved with the surrounding normal skin. It is completely painless despite its size and raw appearance. In dogs a lick granuloma will normally be found only on one of two parts of the body, the anterior aspect of the foreleg or the lateral hock region of the hindleg. The reason for these curious locations becomes apparent when the culprit is caught in the act of licking-they are parts which can be obessively and comfortably licked at leisure whilst the animal is lying down. Some dogs will not only keep licking these self-inflicting lesions but also nibble and chew them, sometimes producing very thickened or bizarre nodular areas of ulceration and pigmentation as the surrounding eqidermis tries in vain to repair the damage. It is unusual for more than one granuloma to be present at one time although they may recur on various limbs over the years. This can be helped by providing more exercise, more human companionship, a holiday away or even another canine playmate. It is not inconceivable that there is some underlying sexual basis to the aberrant obsession with licking. The treatment of a lick granuloma in a dog is often very frustrating for even the most experienced veterinary surgeon. A case which is presented early, before the lesion is more than coin-sized, may need no more than application of a potent corticosteriod ointment with some antibiotic cover under a suitable protective bandage for several days once or twice. Care must be taken not to use an adhesive tape which causes skin irritation to the underlying skin otherwise you may end up with three lesions instead of one! Dogs which will not leave a bandage alone may need an Elizabeth Collar or cutout plastic bucket fitted over the head on to the collar to prevent the seeking tongue from reaching the affected part. Sometimes injection of a soluble cortico steroid directly into the granuloma will suppress the chronic inflammation and allow healing once the dog pays less attention to it. A course of corticosteriod tablets by mouth vvill often achieve similar results but such therapy should be under careful veterinary supervision.
Unfortunately some dogs will keep on licking until the development of a large indolent granuloma which is too big for conservative treatment. It is therefore most important that lesions are treated as early as possible before reaching a size which may finally refuse to heal despite heroic attempts to overcome the problem. Not all uncerated skin plaques turn out to be lick granulomas,. of course, and it may be necessary to take a specimen of those which give rise to suspicions of a tumour or other invasive disease. A new method of treatment which is currently achieving good results in more than two-thirds of chronic lick granulomas is cryotherapy. The affected skin is deep-frozen for several minutes with special freezing instruments. This destroys many of the itch inducing nerve endings in the granuloma as well as getting rid of much of the unwanted fleshy inflamotory tissue. No bandage is applied and although the treated lesion may look rather unpleasant for a few days the results are usually encouraging a reduction in the desire to lick and regrovvth of new skin from the edges. Complete healing may take many weeks and it might be necessary to repeat the cryotherapy once or twice. Healed lick granolomas usually leave a scar because hair follicles are destroyed. Cats too suffer from lick granulomas. Not only will they produce these self inflicted skin lesions down the inside of the hind legs but also on the abdominal areas which cats find easy to lick with their rasp-like tongues. The lesions are not quite as thickened as those found in the dog but may be very rnoist and extensive, sometimes in a straight line. Because many eosinophils are seen under the microscope in histological sections of cat lesions, the term ‘eosinophilic granulorna’ is often used. Treatment in cats is usually a high-dose course of corticosteriod tablets by mouth for one or two weeks or more, perhaps together with an antibiotic. Much more research is needed into lick granulorna so that more effective treatments can be evolved. One aspect of interest is the presence of large numbers of mast cells in most lick granulomas. These cells are well-known releasers of histamine and other substances, thus inviting the theoretical possibility of finding drugs which will suppress the suspected itching sensation and no longer attract the damaging attention of the animal’s tongue.

CAUSES: What causes a lick granuloma to arise in the beginning? Observant owners may notice that one started with a small skin scratch or abrasion which attracted the attention of the dog”s tongue and then failed to heal, gradually enlarging as the licking persisted. However, an initiating wound is often not apparent and it seems that licking of the outwardly normal hairy skin can itself begin the whole process. Several factors may influence whether a lick granuloma arises or not.Firstly there is a definite predisposition in certain breeds of dogs, particularly Labradors, Great Danes and Boxers. It is thus possible that some dogs may inherit a type of skin which reacts excessively when damaged or which produces an itchy and irresistible inflammation. Another factor is a psychological one as many animals suffering from a lick granuloma are obvious victims of boredom such as large clogs left alone with insufficient activity to occupy them. It is therefore not surprising to learn that guide dogs for the blind, although mostly of the Labrador breed, almost never suffer from lick granulomas because they are too busy. An important part of the treatment of this condition is thus aimed at attempting to break the dog’s apparently gratifying habit of licking.