Causes of Scratching & Licking in Dogs
Veterinary & Aquatic Services Department, Drs. Foster & Smith

Dog licking paw

In addition to allergies, there are other diseases which can cause your dog to scratch, lick, or pull on his hair. A short description of these conditions such as mange, cancer, behavioral problems, and infections, along with their diagnosis and treatment, are included in the table below. Many of the more uncommon conditions are listed as well. This large number of conditions 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 licking and scratching are color-coded gray in the table (some may be more common in certain geographical areas).



 
Condition

Description

Symptoms

Diagnosis

Treatment

Acanthosis nigricans Inherited form seen in Dachshunds; secondary form caused by friction, hormonal abnormalities, or hypersensitivities Darkening of the skin; in secondary form see scratching and hair loss History, physical exam; in secondary form, testing to determine underlying cause Primary: No treatment; Secondary: Treat underlying disease; in some cases, steroids and Vitamin E supplementation

Acral lick dermatitis (neurodermatitis)

Self-licking in dogs results in self-trauma; possible causes include anxiety, boredom, stress (e.g., new member in household); licking can develop into an obsessive behavior

Red, hairless, well-circumscribed, sometimes raised lesion usually on the leg; if chronic, will drain

Exclude other causes; history important

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

Allergic and irritant contact dermatitis

An allergic reaction following exposure to antibiotics applied to the skin; metals such as nickel; materials such as rubber, wool, and plastic; and chemicals such as dyes and carpet deodorizers; or inflammation caused by irritating substances such as poison ivy. Generally requires multiple exposures.

Red skin and small bumps or blisters on the areas of skin that are sparsely haired and directly exposed to the offending substance; itching; hair loss in chronic conditions

Patch test, exclusion trials

Restrict exposure to the allergen or contact irritant in the dog's environment; steroids, antihistamines

Atopy (allergic inhalant dermatitis)

Allergic reaction to something airborne, such as pollen, house dust mites, and mold

Licking of feet, inflamed ears, itching, redness, and hair loss; sometimes development of infection or hot spots

Intradermal or serologic (blood) testing for allergies

Reduce exposure to allergen (what the dog is allergic to); steroids, fatty acid supplements, biotin, antihistamines, shampoos, or immunotherapy

Bacterial infection (pyoderma)

See Folliculitis, Staph hypersensitivity

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

     
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
Calcinosis cutis Mineralization of the skin usually due to an excess of corticosteroids; also rarely occurs in kidney failure, or in granulomas and tumors Hard nodules and papules usually on the back, groin, or axilla ulcerate, drain, and develop crusts; severe itching; may become infected; often see other signs of Cushing's disease Skin scrapings, biopsy, history, and other clinical signs, adrenal gland function tests If due to glandular tumors, selegiline, o,p-DDD (Mitotane), or surgical removal of tumor; if due to high steroid doses, withdraw use of steroids slowly

Cheyletiella (rabbit fur mite) mange

Infection with the Cheyletiella mite

Itching, scaliness; some hair loss, if severe

Skin scraping and microscopic examination - the mite is often very difficult to find

Pyrethrin, Permethrin (Do NOT use permethrin on cats.)

Chiggers (harvest mites)

Seasonal disease caused by larvae of the chigger

Itching, bumps usually on feet, abdomen, folds at base of ears

Visualization of mite larvae or microscopic examination of skin scraping

Pyrethrin, Permethrin (Do NOT use permethrin on cats.)

Demodectic mange(red mange, puppy mange)

Infection with the Demodex mite - occurs when the immune system is deficient

Hair loss, scaliness, redness, pustules, ulcers, sometimes itching, darkening of the skin

Skin scraping and microscopic examination

NO Steroids

Amitraz (Mitaban) dips

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

Ear mites

Infection with Otodectes

Intense itching of ears, redness, dark crumbly discharge in ears

Direct visual or microscopic examination of ear discharge

Clean ears and apply medication containing pyrethrin (Ear Miticide)

Epitheliotropic lymphoma (mycosis fungoides) Rare cancer of T lymphocytes seen in older dogs Can take multiple forms: redness with itching and scale; ulcers and loss of pigment; one or more nodules; oral ulcers Needle or other biopsy Poor response to treatments, which include chemotherapy, surgical removal, retinoids, fatty acids

Flea allergy dermatitis (flea bite hypersensitivity)

Severe reaction by the animal 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 dog; steroids and antihistamines for the itching

Folliculitis Infection of the hair follicles, often with staph bacteria; symptoms usually appear on skin with less hair, such as the abdomen (belly) Pustules form in follicles and break open to form 'bull's-eye,' 'annular,' and 'target lesions,' which have crusty centers and red or darkening on the periphery, and 'epidermal collarettes,' which appear as rings of scaly skin; itching may occur; short-coated breeds may develop small tufts of hair which are lost; breeds with long coats may have seborrhea Skin scraping; culture; biopsy Antibiotics for at least 4 weeks - continue antibiotics 10 days beyond the apparent cure; if recurs, look for underlying problem such as allergy or hormonal imbalance

Food Allergies

Allergic reaction to something in the diet

Licking of feet, inflamed ears, itching, redness, and hair loss; sometimes development of infection or hot spots

Food elimination trials

Change in diet

Hookworms

Infection with the larvae (immature forms) of hookworms

Red bumps, usually on feet, rough foot pads, abnormal nail growth, itching

Physical exam, history of poor sanitation

Treat for intestinal infection; move dog to different environment

Hot spots (acute moist dermatitis)

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

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*), Permethrin (Do NOT use permethrin on cats.)

Lymphoma

Common cancer in dogs; can involve the skin

Itching, ulcers, nodules, redness

Biopsy

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

Malassezia

Usually follows some other underlying disease

Itching, redness, hair loss, greasy scales; if chronic, develop hyperpigmentation

Skin scraping/smear and microscopic examination, culture

Treat underlying disease; oral ketoconazole; miconazole shampoos

Pelodera dermatitis

Accidental infection with larvae from a non-parasitic worm that lives in straw and other organic material

Affects areas of skin touching ground; intense itching, redness, hair loss, papules, crusts, scales

Skin scraping and microscopic examination

Remove bedding; mild antibacterial shampoo; steroids if necessary to control itching

Pemphigus foliaceus The most common form of pemphigus in the dog; an autoimmune disease; some breeds are at increased risk 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 animals may have fever and loss of appetite History, physical exam, skin scraping and biopsy Corticosteroids, other immunosuppressive therapy, gold injections
Pyoderma-superficial

See Folliculitis, Staph hypersensitivity

       

Ringworm

Infection with several types of fungus

Hair loss, scaliness, crusty areas, pustules, vesicles, some itching; can develop a draining nodule called a 'kerion'

Culture

Miconazole, lime sulfur dips; oral griseofulvin or itraconazole

Sarcoptic mange

Infection with the Sarcoptes mite

Intense itching and self-trauma, hair loss, papules, crusts, and scales

Skin scraping and microscopic examination - the mite is often very difficult to find

Amitraz (Mitaban) dips (off-label use*); ivermectin (off-label use*)

Schnauzer comedo syndrome Uncommon; only seen in Miniature Schnauzers Comedones (black heads) on back, mild itching; may see secondary infection, thinning of hair; small crusts may develop Clinical signs, breed, skin biopsy Long-term antiseborrheic shampoos; sometimes antibiotics and retinoids
Sebaceous adenitis Sebaceous glands are destroyed, cause unknown; certain breeds more susceptible Short-haired breeds: circular areas of hair loss with fine scale; long-haired breeds: more widespread hair loss and scale, hair mats easily; may see itching in all breeds Clinical signs, breed, skin biopsy Antiseborrheic shampoos, fatty acid supplements; in more severe cases, steroids, retinoids
Seborrhea Can be primary (inherited) or secondary (resulting from other disease processes such as allergies, hypothyroidism) Scales; depending upon the type, may have a dry or oily coat; odor; some scratching; may see hair loss Blood tests, skin scraping, etc., to find underlying cause Treat underlying cause if present; antiseborrheic shampoos; fatty acid supplements
Skin cancer See Lymphoma      
Skin fold pyoderma (intertrigo) Inflammation of skin that contacts other skin, e.g., lips, facial folds (on Bulldogs, for instance), vulva, tail, toes, and bodies of obese dogs Red, oozing area; crusts; often becomes infected and may develop odor Clinical signs; skin scraping 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
Staph hypersensitivity Rare disease in dogs caused by an allergic reaction to the bacteria Staphylococcus; often occurs in the presence of other skin diseases Red skin, pustules, vesicles, severe itching, and sometimes crusts Culture, biopsy, intradermal allergy test Treat any underlying disease; antibiotics
Superficial necrolytic dermatitis of Miniature Schnauzers Skin reaction to shampoos (usually insecticidal or medicated) Papules, ulcers with drainage; develop 2-3 days after exposure to the shampoo; may also see fever and depression Breed, history of exposure, clinical signs Treat symptomatically
Tail dock neuroma Nerve regrowth after tail docking causes symptoms Nodule at site of docking, itching with self-mutilation, hair loss, and hyperpigmentation History and symptoms Surgical removal
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
Urticaria (hives) Reaction, often allergic, to insect bite, drug, vaccine, sunlight, etc. Multiple swellings, with hair standing up over swellings; may itch History, physical exam Often resolves on its own; in the case of allergic reactions, antihistamines, epinephrine, or corticosteroids depending upon severity

* 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 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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