skin

SKIN DISORDERS

Skin problems in dogs are a common occurrence, the most common variety of problems encountered include parasitic infestations such as fleas, mange or lice. Allergies are common and can be caused by fleas, food, contact with sometimes mundane substances, or in the form of atopy, a hypersensitivity reaction within the skin. Pyoderma is a bacterial skin infection, often developing as a result of an underlying problem and is extremely common in the dog compared to other species. Fungal infections such as ringworm, and yeast infections such as Malassezia can occur as independent infectious agents, or as a complication of another problem. Environmental skin disease caused by contact irritation is common in some breeds, Nutritional skin problems are now rare but vitamin A and zinc deficiencies can cause problems if the diet is not properly balanced. Psychogenic skin disorders arise as a result of excessive licking or chewing of the skin for behavioural reasons, although sometimes there can be underlying infection or allergy problems. Seborrhoea is a group of disorders affecting the keratin layers of the skin, leading to a greasy or dry coat, and finally endocrine problems are hormonal imbalances which can manifest themselves through skin or coat changes.

Differentiating between these problems is not always easy, sometimes the cause is obvious in the cases where parasites such as fleas or lice can be found in the coat, other times more complex investigation is required. Many times the primary problem is not the skin abnormality but is related to other body systems.

Your veterinary surgeon will wish to know when the problem first started , the age of the animal, the first abnormality noted, whether the problem has been sudden or gradual in onset, which area of the body is affected, whether the condition has spread, does it itch, is there a seasonal variation, are other animals or people affected, diet, any change in your pets environment, any previous treatment and responses to treatment, and other facts relating to the general health of the animal.

Simple tests that can be performed to aid the diagnosis include the following:

Combing; fine toothed combs can be useful in collecting surface parasites such as fleas, flea dirt, and lice.
Skin scrapings; this involves using a sharp blade to remove the surface layers of the skin for microscopic examination, it is essential for the diagnosis of sarcoptic and demodectic mange
Scale collection and examination; scale and dirt is knocked out of the coat and collected, or collected on a sellotape strip by repeatedly applying it to the animals coat and then examined microscopically. It can reveal parasitic eggs, lice, and cheyletiella mites.
Woods lamp; this is an ultraviolet light which will cause some strains of ringworm to fluoresce. It does not occur with all ringworm strains so a negative result does not rule out ringworm.
Fungal culture; this is the only certain means of identifying fungi, plucked hairs are placed on a growth medium to stimulate fungal growth, it can take up to 2-3 weeks to produce a result.

Other, more complex investigations, that can be carried out include:

Bacteriology; involves attempting to grow and identify the bacteria involved in skin infections in order to find appropriate antibiotic therapy, most cases of pyoderma involve a bacterium called Stapllylococcus intermedius so bacteriology may only be carried out if treatment for this has been unsuccessful.
Impression smears; these can be useful in certain types of skin tumours and immune skin problems to examine cells or fluid from skin lesions.
Blood sampling; often used in endocrine skin problems to measure certain hormone levels.
Intradermal skin testing; this involves injection of certain substances into the skin to asses the degree of inflammatory response and is particularly useful in allergic forms of skin disease.

In some cases inconclusive results can be obtained and your veterinary surgeon may opt for trial therapy to decide the nature of the problem. He/she is likely to use a single treatment for a period of time and then assess the response, this is particularly useful in some cases of parasitic and bacterial infection, and may indeed be carried out in preference to some of the tests outlined above.

If further investigation is required after this then it may be of value to take skin biopsies for histopathological examination.