Causes of Scratching & Licking in Dogs

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.