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Causes of Skin Ulcers & Draining, Oozing, or Crusty Lesions on Cats
Veterinary & Aquatic Services Department, Drs. Foster & Smith
skin conditions
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Causes of Skin Ulcers and Draining, Oozing, or Crusty Lesions on Cats Causes of Skin Ulcers and Draining, Oozing, or Crusty Lesions on Cats

The first sign of a skin problem may be a crusty area on the skin, nose, or foot. In other cases, skin problems which may start out small can progress and develop into more extensive lesions. They may open, drain, and then develop a crusty surface. In some instances there may be hair loss, and the surface of the skin can become red and oozing, and ulcers may develop. Most of the conditions which can cause these lesions are included in the table below. This extensive listing helps you understand why a quick diagnosis may be difficult to make and various diagnostic tests may need to be performed. The most common conditions causing these lesions are color-coded gray in the table (some may be more common in certain geographical areas).


 
Condition Description Symptoms Diagnosis Treatment
Abscesses Accumulation of pus; may or may not be caused by an infection; in cats, often due to bite wounds These may appear as firm, fluid-filled nodules of varying shapes and sizes, with small crusty area at puncture site; if due to infection, cat may have fever, loss of appetite, depression; may open and drain History, physical exam, needle aspirate Surgically open, drain, and flush; if infected, administer appropriate antibiotics
Aspergillosis Fungal infection which usually enters through the nose Ulcerated, draining lesion on nose; also see drainage from nostrils and pain Microscopic examination of drainage; biopsy; blood tests Antifungal medications

Bacterial infection (pyoderma)

See Folliculitis, Pyoderma-deep

Often occurs as a result of another condition such as a parasite, allergic, or hormonal conditon

     
Basal cell tumors Most common skin tumor in cats; benign tumors; may become cancerous, slow-growing tumors which rarely metastasize Single, sometimes fluid-filled nodules which may ulcerate; usually on the head, neck, and chest; may be hyperpigmented Biopsy Surgical removal (if benign, surgical removal is optional)
Bee, wasp, hornet stings Skin reactions can vary dramatically in severity Immediately after the bite, see swelling, redness, pain, possibly itching; subsequently may develop extensive ulcers with draining; may develop hives or anaphylaxis History, physical exam Antihistamines, steroids; wet dressings if ulcerated; protect the area from self-inflicted trauma
Bite wounds

See Abscesses

       
Bowen's disease A rare type of squamous cell carcinoma in which multiple lesions develop Lesions start out as thickened, dark, raised and well-delineated; progress to ulcers and crusts and bleed easily; found on the head, neck, shoulders, and forelegs Biopsy Lesions may come and go and are not always treated; some anti-cancer drugs and radiation have been tried with mixed results
Burns Appearance and treatment depend upon severity of burn Lesions may not appear until 24-48 hours after the exposure; skin hard and dry; blisters rarely seen; if severe (full thickness of the skin is affected) see necrosis and sloughing of skin 7-14 days after the burn occurs History, physical examination Immediately cool affected area if burn occurred in the last 2 hours; further treatment depends on severity; keep area clean; prevent secondary infections, topical silver sulfadiazine is useful; treat other symptoms which may occur: dehydration, shock, etc.; pain management; no steroids
Coccidioidomycosis Caused by the fungus Coccidioides immitis found in the soil in the Southwestern U.S. Draining nodules, fever, weight loss; unlike dogs, no respiratory signs Microscopic examination of drainage; blood test Ketoconazole, itraconazole
Cold agglutinin disease Rare disease in which proteins in the blood coagulate in cold temperature and block small blood vessels causing skin damage; may be a result of lead poisoning or autoimmune disease Redness, ulcers, possibly necrosis; lesions usually on ears, tail, and extremities History of exposure to cold; special blood tests including the Coomb's test; biopsy Treat any underlying cause; avoid cold; steroids and immunosuppressants
Cryptococcosis Fungal infection often transmitted through bird droppings; more common in cats with suppressed immune systems Nodules often over the nose which may ulcerate; many other signs depending on what other body systems are infected Microscopic exam of discharge, blood tests, culture, biopsy; look for underlying cause of immunosuppression Itraconazole
Drug or injection reaction Rare skin reaction to a drug which is inhaled, given orally, or applied topically; more common with penicillins, sulfonamides, and cephalosporins; usually occurs within 2 weeks of giving the drug Can vary widely and may include itching, hair loss, redness, swelling, papules, crusts, ulcers, and draining wounds History of being treated with a drug, symptoms, biopsy Discontinue offending drug; treat symptomatically
Eosinophilic granuloma Part of the common eosinophilic allergic syndrome in cats which includes eosinophilic plaques, miliary dermatitis, and rodent ulcers Elongated, raised, oozing, and possibly ulcerated lesions, with hair loss; may be single or multiple; often on back of thighs Microscopic examination of swab from lesion, biopsy, CBC (find increased eosinophils); look for underlying cause, e.g., parasites, food allergy, atopy Treat underlying cause if found; corticosteroids; fatty acid supplements; immunosuppressive drugs in severe cases
Eosinophilic plaque Part of the common eosinophilic allergic syndrome in cats; see also eosinophilic granulomas, miliary dermatitis, and rodent ulcer Intense itching; raised, oval, oozing, and possibly ulcerated lesions; may be single or multiple; often on abdomen and thighs Microscopic examination of swab from lesion, biopsy, CBC (find increased eosinophils); look for underlying cause, e.g., parasites, food allergy, atopy Treat underlying cause if found; corticosteroids; fatty acid supplements; immunosuppressive drugs in severe cases
Epitheliotropic lymphoma (mycosis fungoides) Rare cancer of T lymphocytes seen in older cats; may be associated with FeLV Redness, itching, scales, ulcerated nodules Needle or other biopsy Poor response to treatments which include chemotherapy, surgical removal, retinoids, fatty acids
Erythema multiforme Hypersensitivity reaction to infections or drugs; may also be caused by cancer or other diseases Hair loss, 'bull's eye' lesions, and vesicles often around mouth, ears, groin and axilla; in some instances, ulcers develop; depression, fever History, clinical signs, rule out other diseases causing similar signs; skin biopsy Treat or remove underlying cause
Feline herpesvirus and calicivirus Commonly see respiratory signs; skin lesions may occur in cats who are stressed or immunosuppressed May see ulcers on feet and head; upper respiratory signs and oral ulcers usually present Virus isolation, biopsy; check for underlying disease or stress Good nutrition, antibiotics, antiviral medications, NO steroids
Feline leprosy Caused by the bacteria 'Mycobacterium'; usually seen in young cats Single or multiple nodules which may drain; usually on head or neck; nonpainful; cat does not show other signs of disease Biopsy, culture Surgical removal, anti-mycobacterial drugs such as rifampin or clofazimine
Feline pox Viral disease; outdoor cats more commonly affected; presumably transmitted by bite wounds Nodule at the site of a previous bite wound; progresses to multiple nodules which may ulcerate and have crusts; may itch History, physical exam; biopsy; specialized testing to identify the virus Lesions usually resolve in 3-4 weeks; anitbiotics for any secondary infection; antihistamines for itching; no steroids; in some cats, lesions progress and do not respond to treatment
Fibrosarcoma Rapidly growing, invasive tumor; may occur at the site of a vaccination or injection, especially in cats; may be induced by a form of FeLV Irregular-shaped, firm nodule; may ulcerate Biopsy Surgical removal, however, since tumor is invasive need to remove large area around tumor, sometimes including large masses of muscle and bone; if tumor is on a leg, amputation of the leg is commonly recommended; surgery may be combined with chemotherapy and radiation

Flea allergy dermatitis (flea bite hypersensitivity)

Severe reaction by the cat to the saliva of the flea

Intense itching, redness, hair loss papules, crusts, and scales; sometimes development of infection or hot spots

Presence of fleas; reaction to intradermal testing

Flea Control in the environment and on the cat; steroids and antihistamines for the itching

Folliculitis Infection of the hair follicles; symptoms usually appear on face, neck, and head Pustules develop in the hair follicles and open and form crusts; may itch and develop hair loss Skin scraping; culture; biopsy; look for underlying condition such as allergy or FIV Antibiotics, usually for 3-4 weeks; treat any underlying condition
Frostbite Appearance and treatment depend upon severity of exposure Ears, tail tip, and feet most often affected; when frozen skin is pale and cold; upon thawing, areas are red and painful; if severe, the skin may be sloughed (1-2 weeks later) History, clinical signs Rapidly thaw affected areas with warm water; surgical intervention if severe. Avoid thawing and refreezing since this results in extensive skin damage.
Granulomas May be due to infections; the body's reaction to foreign material such as plant material (e.g., foxtail) and suture material; other constant irritation; or unknown causes Solid firm nodules of varying sizes; those due to foreign bodies often have draining tracts; may develop hair loss, ulcers, and secondary infections History, clinical signs, biopsy, surgical exploratory Surgical removal of the foreign body (in the case of plant material, tracts may be extensive and require major surgery); antibiotics if infected; treat any other underlying cause
Hemangiosarcoma Malignant, invasive tumor more common on sun-damaged skin Blue to reddish black nodule; usually on ears, head, legs, groin, and axillae; often ulcerate Biopsy Surgical removal; need to remove large area around the tumor; if tumor is on a leg, amputation of the leg is commonly recommended
Histoplasmosis Fungal infection which can rarely cause skin lesions Ulcerated and draining nodules; most commonly see respiratory and gastrointestinal symptoms Needle aspirate or biopsy Ketoconazole, itraconazole

Hot spots (acute moist dermatitis)

Result from allergies, flea bites, mange, anal gland disease, poor grooming, ear infections, plant awns or burs, arthritis

Hair loss; red, moist, oozing skin; constant licking or scratching

Physical exam and history

Treat underlying condition; clean area; apply Domeboro solution; topical and/or oral antibiotics and steroids

Hyperthyroidism Approximately 1/3 of cats with this disease will have skin lesions; caused by excess secretion of thyroid hormone Hair loss; hair easily pulled out; seborrhea; cats may overgroom and cause 'hot spots' Physical exam; blood testing for thyroid hormones Remove part of thyroid; radioactive iodine therapy; methimazole

Lice

Infection with several species of lice

Variable: itching, hair loss, crusts, rough hair coat

Finding lice or nits on skin or hair

Pyrethrin, ivermectin (off-label use*)

Lupus erythematosus Autoimmune disease affecting many body systems inlcuding joints, kidneys, muscles, nervous system Skin lesions may include thickening or ulcers of the foot pads, scaling, and recurring bacterial infections with pustules Special blood tests (LE test); biopsy Prednisone and other immunosuppressive drugs; treat underlying infections

Lymphoma

Type of cancer; may occur in other organs without skin involvement

Nodules with ulcers; redness

Biopsy

Surgery, chemotherapy, radiation; lymphoma of the skin does not usually respond to treatment as well as other lymphomas

Mammary cancer Most common in unspayed females; in cats, 85% are malignant Single or multiple nodules under the skin, of varying sizes, often irregular in shape; may ulcerate and drain Biopsy Surgical removal
Mast cell tumor Common cancer which is graded from 1-4: Grade 1 is one slow-growing tumor, and Grade 4 is rapidly growing malignant tumors with metastasis; in cats most are Grade 1 Tumors may be of various sizes, appearances, and numbers Biopsy to grade the tumors which determines treatment and prognosis Depends upon grade; surgical removal, taking large area around tumor; chemotherapy; prednisone; radiation
Melanoma Malignant tumor; uncommon in cats Usually single, dark-colored nodule which often ulcerates Biopsy Surgical removal, taking large area around tumor
Miliary dermatitis in cats Part of the common eosinophilic allergic syndrome in cats which includes eosinophilic granulomas, eosinophilic plaques, and rodent ulcers; may also be associated with infections, autoimmune diseases, hormonal disorders, and nutritional deficiencies Multiple small crusty bumps, usually over hips, neck, and back of thighs; moderate to severe itching Microscopic examination of swab from lesion, biopsy, CBC (find increased eosinophils); look for underlying cause, e.g., parasites, food allergy, atopy Treat underlying cause if found; corticosteroids; fatty acid supplements
Mosquito bite hypersensitivity Severe allergic reaction to mosquito bites; lesions most common on nose and ear tips - also footpads, lips, and chin Acute lesions are red, raised, and oozing; with time develop hair loss, scales, nodules and pigment changes; some cats develop fever and swollen lymph nodes History of exposure to mosquitoes; lesions resolve when cat is hospitalized or otherwise restricted from exposure to mosquitoes Restrict exposure to mosquitoes, insect repellents, prednisone
Nocardia Bacterial infection usually acquired from a puncture wound Usually see respiratory signs; skin lesions include draining nodules Bacterial culture, microscopic examination of drainage Poor prognosis; antibiotics

Notoedric mange

Infection with the Notoedres mite

Intense itching and self-trauma, skin thickening, gray crusts develop

Skin scraping and microscopic examination

Lime sulfur dips, ivermectin (off-label use*)

Panniculitis May be caused by trauma, foreign bodies, infections, autoimmune diseases, or unknown causes Deep-seated nodules, often ulcerated and draining; usually on the body vs. the head or limbs; may see loss of appetite, depression Microscopic exam of drainage; biopsy; tests to rule out other causes Surgical removal; if multiple lesions, prednisone and Vitamin E; may need long-term treatment
Pemphigus erythematosus Less severe form of pemphigus foliaceus, an autoimmune disease; exposure to sunlight may play a role in its development Pustules, drainage and crusts; usually on face and ears History, physical exam, skin scraping and biopsy Topical and oral steriods; other immunosuppressives
Pemphigus foliaceus The most common form of pemphigus in the cat; an autoimmune disease Often affects feet and head; starts with pustules and progresses to severe crusting; depigmentation of the nose is common; itching may occur; if footpads and nails affected often see lameness; symptoms wax and wane; severely affected cats may have fever and loss of appetite History, physical exam, skin scraping and biopsy Corticosteroids, other immunosuppressive therapy, gold injections
Pemphigus vulgaris A rare form of pemphigus, an autoimmune disease Large vesicles which break open, ulcerate and develop thick crusts; lesions often found in the mouth Biopsy Poor prognosis; prednisolone and other immunosuppressants
Phaeohyphomycosis Caused by wound contamination with a fungus A single nodule on the legs or multiple ulcerated and draining nodules over the body Microscopic examination of drainage, culture, biopsy Surgical removal though often recur; possible antifungal medications

Psychogenic (neurogenic) dermatitis

Self-licking in cats results in self-trauma; possible causes include anxiety, boredom, stress (e.g., new member in household)

Symmetrical hair loss, sometimes ulcers, on abdomen, groin, along the back

Exclude other causes; history important

Relieve underlying cause e.g., anxiety; restrict licking; behavior modifying medication may be necessary

Pyoderma-deep Bacterial infections of skin and underlying tissue often secondary to another skin disease such as self-inflicted trauma, wounds, acral lick granulomas, allergies, seborrhea Ulcerated pustules or nodules, draining tracts, crusts, thickened skin Skin scrapings, biopsy, culture Clip and cleanse area; antibiotics, prevent self-trauma (licking, scratching), NO steroids
Pyoderma-superficial

See Folliculitis

       
Pythiosis Caused by an aquatic mold Ulcerated draining nodules on the legs, head, and base of tail which, may itch; often see other signs of illness due to infection of the gastrointestinal tract Microscopic examination of drainage; biopsy Often fatal; surgical removal
Ringworm

Infection with several types of fungus

Hair loss, scaliness, crusty areas, some itching

Culture

Miconazole, lime sulfur dips; oral griseofulvin or itraconazole; ringworm vaccine

Rodent (indolent) ulcer Part of the common eosinophilic allergic syndrome in cats which includes eosinophilic granulomas, eosinophilic plaques, and miliary dermatitis Ulcer forms on the upper lip; ulcer can be very deep Skin scrapings, biopsy Steroids; sometimes antibiotics; look for underlying cause
Sebaceous gland tumor Rare in cats; rarely spreads or recurs; several types Nodules which may ulcerate; usually on the head and legs Biopsy Surgical removal if invasive; if a benign lesion, removal is optional
Skin cancer See specific type, e.g., Fibrosarcoma, Melanoma, Squamous cell carcinoma, Mast cell tumor, Lymphoma      
Skin fold pyoderma (intertrigo) Inflammation of skin that contacts other skin, e.g., lips, facial folds (on Persians, for instance), vulva, tail, toes, and bodies of obese cats Red, oozing area; crusts; often becomes infected and may develop odor Clinical signs; skin scrapings and tape impression smears Clip and cleanse area; keep area clean; medicated shampoos; topical antibiotics; treat underlying condition, e.g., increased tears from eye disease, obesity, allergy
Solar dermatosis (sunburn) Skin reaction to sunlight; more common in cats with white ears Redness, hair loss, and scaling on nose and ears, later crusts and ulcers History, breed, physical exam, skin biopsy Must avoid further sun exposure, especially 9 am - 3 pm; sunblock, steroids
Spider bites/eosinophilic folliculitis Bites from some spiders and caterpillars contain strong toxins; usually appear on the nose of dogs and paws of cats Immediately after the bite, swelling, redness, pain; subsequently may develop extensive ulcers with draining History, biopsy Corticosteroids, wet dressings, protect the area from self-inflicted trauma; may develop permanent loss of hair and scarring
Sporotrichosis Caused by the fungus Sporothrix schenckii which generaly enters through a puncture wound Raised nodules with multiple draining tracts; cats may develop fever, depression, and loss of appetite Microscopic exam of drainage; culture; fluorescent antibody test Potassium iodide, ketoconazole, itraconazole
Squamous cell carcinoma Common malignant tumor; may occur more commonly in sun-damaged or chronically irritated skin Two forms: cauliflower-like lesions, often ulcerated more common on ears; crusted ulcers on head or feet (around claws) Biopsy Surgical removal, radiation, hyperthermia
Stud tail (tail gland hyperplasia) A sebaceous gland (on the top of the tail near its base) enlarges; most often occurs in confined, unneutered males Oily area, hair loss, and crusts on area over gland; may become hyperpigmented Clinical signs Castration usually does not resolve the condition; antiseborrheic shampoos, retinoids; if confined, allow cat more freedom
Tick bites Ticks cause a local inflammation in the skin, even when the entire tick is removed Nodule and redness at site of the bite; may itch and develop crusts; may last several months History Remove the tick; use a tick preventive; allow nodule to resolve on its own
Toxic epidermal necrolysis Severe immune reaction to infections or drugs; may also be caused by cancer or other diseases Vesicles, erosions, ulcers, crusts over large areas of the body, especially mouth and feet; may look like a severe burn History, clinical signs, skin biopsy Prognosis is poor; treat underlying condition; give supportive care, corticosteroids may be helpful
Urine scald Occurs when skin is in prolonged contact with urine, e.g., recumbent cats Red, oozing lesions in areas exposed to urine History, clinical signs Clip and cleanse area; keep it clean; place cat on wire or plastic rack or grate; change bedding often; medicated shampoos; topical antibiotics
Zygomycosis Uncommon fungal disease Draining nodules; may also see pneumonia, vomiting, or jaundice depending upon the body organs involved Microscopic examination of the drainage; biopsy Often fatal; surgical removal of nodules followed by amphotericin B, benzimidazoles, or potassium iodide

* off-label use: medication used to treat a condition for which it was not developed (or licensed). A large number of medications fall under this category. Research has almost always been performed to determine the effectiveness and safety of the product, but the manufacturer has not undertaken the lengthy process required for licensure.

References

Birchard, SJ; Sherding, RG (eds) Saunders Manual of Small Animal Practice. W.B. Saunders Co. Philadelphia, PA; 1994.

Greene, CE (ed). Infectious Diseases of the Dog and Cat. W.B. Saunders Co. Philadelphia, PA; 1998.

Griffin, C.; Kwochka, K.; Macdonald, J. Current Veterinary Dermatology. Mosby Publications. Linn, MO; 1993.

McKeever, PJ; Harvey, RG. Skin Diseases of the Dog and Cat. Iowa State University Press. Ames, Iowa; 1998.

Paterson, S. Skin Diseases of the Cat. Blackwell Science Ltd. London, England; 2000.

Paterson, S. Skin Diseases of the Dog. Blackwell Science Ltd. London, England; 1998.

Scott, D; Miller, W; Griffin, C. Muller and Kirk's Small Animal Dermatology. W.B. Saunders Co. Philadelphia, PA; 1995.

 
References and Further Reading

Birchard, SJ; Sherding, RG (eds.) Saunders Manual of Small Animal Practice. W.B. Saunders Co. Philadelphia, PA; 1994.

Greene, CE (ed.) Infectious Diseases of the Dog and Cat. W.B. Saunders Co. Philadelphia, PA; 1998.

Griffin, C; Kwochka, K; Macdonald, J. Current Veterinary Dermatology. Mosby Publications. Linn, MO; 1993.

McKeever, PJ; Harvey, RG. Skin Diseases of the Dog and Cat. Iowa State University Press. Ames, Iowa; 1998.

Paterson, S. Skin Diseases of the Cat. Blackwell Science Ltd. London, England; 2000.

Paterson, S. Skin Diseases of the Dog. Blackwell Science Ltd. London, England; 1998.

Scott, D; Miller, W; Griffin, C. Muller and Kirk's Small Animal Dermatology. W.B. Saunders Co. Philadelphia, PA; 1995.

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