Dog Skin Lesions

"Dog skin lesions, in terms of definition are dead tissues caused by any reason, such as an injury. Skin lesions in dogs are simply an advanced complication of various canine skin disorders. Canine skin lesions may be caused by any parasitic infestation (mites, lice, fleas), bacterial infection, injury, allergy, cancerous cells and inflammation. Any factor which can cause a skin injury, will lead to a skin lesion. Puss is a primary component of a lesion. Puss is comprised of dead tissues, inflammatory and/or lymphatic tissues, dead causative agents and water. Lesions can be diagnosed with methodical clinical and laboratory examination. Treatment involves cleansing the area, removal of dead tissues and post operational care."

Causes of Dog Skin Lesions

1. Abscesses; An abscess is the accumulation of dead skin tissues. Any bacterial, parasitic or traumatic agent can cause an abscess. Abscess formation is actually the response of body towards damaged tissues. Injured, turbid (if it contains foreign particles) and potentially weakened skin tissues are executed by immune system cells (attacked) as they may cause severe damage to surrounding tissues and can also serve as a home to opportunistic secondary bacterial or viral agents.

   Immune system cells are known as neutrophil, basophil, lymphocytes and monocytes; collectively called WBC’s. Amongst them, lymphocytes have three types; B – Cells, T – Cells and Natural Killer Cells. T – Cells are further divided as helper, cytotoxic and control cells. The function of Natural Killer Cells & Cytotoxic cells of T – Cells is to control infection and further injury by killing infected, injured and weakened tissues which are more susceptible to pathogens or foreign bodies and pressure. Here, the phenomenon of these two types of cells is collectively referred as “Executed by immune cells.” 

2. Dermatitis & Pyoderma; Dermatitis refers to infected or inflamed skin, while pyoderma is a symptom of skin dermatitis caused by bacterial agents. Dermatitis is usually caused by a secondary bacterial or viral infections occurring after a parasitic or allergic condition. Dog skin lesions caused by dermatitis appears as red areas on the skin, alopecia (hair loss) and skin crusts. Chronic cases are filled with puss and draining puss. 
3. Fungus; Skin fungus is a common reason for dog skin lesions. Several fungal problems like that in aspergillosis, cryptococcosis and ring worm can cause skin lesions. Papular, crusty and draining lesions are seen at the site of infection. Localized and generalized alopecia (hair loss in one area or all over the body respectively) at and around lesions can be seen. 
4. Parasitic Infestations; Demodectic mange is a common example; lesions appear on the dorsal surface (back), neck and head. Flea infestation also causes lesions on dog skin. Skin appears red, alopecic & crusty, while in chronic cases puss may occur. In most parasitic infestations, where deep tissues of skin are involved, skin lesions are cause itch and are complicated. 
5. Skin Cancer; Dogs affected by malignant (fast growing, spreading) tumors commonly have skin lesions. Metastatic (growth) activity of cancerous cells lead to the death of existing tissues & suppresses the immune system, making the skin appear rough, alopecic (hair loss) & in most cases lesions are distributed all over the body. Fibrosarcomas, Melanomas, Squamous cells carcinomas, Mast cell tumor and Lymphoma are some examples of such dog skin tumors & skin cancers. 
6. Allergies; Allergies can cause lumpy, reddened and itchy skin initially, which can in turn lead to self injury and licking by the dog which converts the area into a skin lesion. Atopy (seasonal allergy), flea–bite hypersensitivity, wasp or flies bite allergies and food born allergies are some common examples. 
7. Physical Injuries; Trauma due to an accidents, burns and wounds are some examples of such conditions which can cause dog skin lesions.

Diagnosis of Dog Skin Lesions

While diagnosing canine skin lesions, there are some points that need to be remembered. 1. Skin lesions are always contaminated by dead tissues, puss and pollutants. 2. Skin lesions may be identified by the condition of the surrounding healthy tissues, which are always inflamed & reddened. 3. A history of the condition is helpful in making a diagnosis.

Treatment of Dog Skin Lesions:

Surgical opening and complete drainage help with recovery, particularly when the canine skin lesion is localized to one area of the dog. A generalized treatment plan should be followed in order to remove the underlying cause of the dog skin lesions. Cancerous cells can only be treated by surgical resection or radiation therapy. Similarly antibiotic therapy is the only option to overcome secondary bacterial infections. Anti–Allergic drugs or an anti–histamine can help to reduce the chances of skin allergy, a common cause of skin lesions in dogs. Physical injuries and trauma should be carefully assessed before treating with a plan put in place for supportive care and nursing. A homeopathic remedy such as PetAlive Skin and Coat Tonic may provide an added level of support.

1. Surgical resection is the preferred approach. In different forms of dog skin tumors, the extent of the surgery may differ. In mast cell tumors and squamous cell carcinomas, aggressive and timely surgical resection is required, while the amount of surgery required for a Histiocytoma is very low. Tests for blood type, hemoglobin level and screening are required prior to surgery, along with willingness of the dog owner. 

References:

The Merck Veterinary Manual 

Paterson. Skin Diseases of Dog – Revised Edition (Blackwell Science Ltd. 2000)