SKIN DISORDERS AND ALOPECIA IN DOGS
Skin disorders are one of the most common reasons pets visit their veterinarians. Problems can develop wherever there is skin, including the ears, around the lips, the bottom of paws, and around the anus. Whatever the symptoms, problems with your pet’s skin are hard to ignore. Although the causes are varied, most skin problems make themselves known with one or more of the following signs: itchiness (scratching, licking, chewing, rubbing, scooting-dragging the bottom across the floor, shaking the head), sores, rashes, hair loss or a thinning coat, bumps, seeing fleas or ticks, or noticing a bad smell, even after bathing. One of the most common sign of skin disorders is hair loss which is called as alopecia.
There are numerous causes for alopecia. The loss of hair normally results from an underlying cause which can range from basic allergies to metabolic disorders to inherited diseases. The causes are divided into two main categories Hereditary and Acquired. Hereditary alopecia is genetic and is passed from parents to offspring. Some hereditary causes are black hair follicle dysplasia and color dilution alopecia. In certain breeds, such as the Chinese Crested, this alopecia trait has been selected for. Acquired alopecia is separated into two divisions: inflammatory and non-inflammatory. The most common causes of alopecia are normally found in the acquired inflammatory category. Some examples include food allergies, flea bite allergies, folliculitis, and sarcoptic mange. Acquired non-inflammatory types are also common and include acral lick dermatitis, calluses, and gestational hair loss.
Understanding that there are over 160 different skin disorders of dogs, some of which create chronic difficulties, is key in helping your veterinarian solve the issue at hand. As a team, you and us as veterinarians should be proactive in defining the problem accurately and in a timely manner. In order to achieve satisfactory results, it will require the doctor’s expertise and perseverance coupled with your permission and financial commitment.
There are few challenges in veterinary medicine more daunting than treating a patient for a long-term skin disorder. Chronic dermatitis cases take up about 10 percent of animal hospital file folders; and these patient folders tend to be the thickest due to the multiple pages of patient history, lab test results, biopsy reports, medications and supplements dispensed, and even dermatology specialist referral summaries. Reading through all that data you would find an oft-repeated theme … “Control is the goal since for sure there’s no cure.”
Curable vs. Incurable
To simplify a bit, there are just two kinds of skin disorders in dogs: curable and incurable. Veterinarians need to understand what is really happening to and within the skin before appropriate therapeutic strategies can be employed. Since it takes a new, healthy skin cell about four weeks to mature and be present near the skin surface even curable skin diseases may take weeks to resolve. For the incurable cases, controlling an ongoing skin disorder through selected diets, medications, shampoos, sprays, fatty acids and vitamin supplements is the best we can do.
Managing a chronic skin disorder presupposes that an exact diagnosis has been established. Making that diagnosis requires certain diagnostic protocols be done so that the doctor has a clear understanding of the pathological processes impacting the patient. A multitude of different causes may very well manifest themselves in very similar appearing visual signs.
For example “itchy skin” (pruritus) is not a diagnosis, nor is “allergy.” The veterinarian needs to establish what is causing the pruritus and to what the dog is allergic. Diligent detective work has to be done and it’s no small task, as evidenced by a recently published veterinary dermatology textbook that lists over 160 skin disorders of dogs!
Not to find yourself in a situation where you leave the veterinary clinic with yet another assortment of medications or skin care products, and the plan of action is “let’s try these for a while and we’ll see if they help,” we need to insist on a more proactive approach to actually obtain a definitive diagnosis. It’s time to get busy with whatever testing is needed to find the cause of the dog’s skin troubles. Only then can we recognize the curable from the controllable.
The treatment prescribed will depend on what is causing the alopecia. In most cases treating the underlying cause will stop hair loss and allow for new growth to occur. For cases where a diagnosis has not yet been made, medicated shampoos and vitamin supplements may be used to help facilitate new hair growth but not cure the disease. Once the cause has been determined the prognosis that the dog’s hair will return is good, although it may take months for the coat to completely return to normal.
This extensive list helps you understand why a quick diagnosis may be difficult to make, and various diagnostic tests may need to be performed.
| Condition | Description | Symptoms | Diagnosis |
| 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 |
| 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 behaviour | Red, hairless, well-circumscribed, sometimes raised lesion usually on the leg; if chronic, will drain | Exclude other causes; history important |
| Adrenal sex hormone responsive dermatosis | More common in Pomeranians, Chows, Keeshonden, and Samoyeds | Hair loss starts on neck, tail, back of thighs, and progresses to trunk; dog appears to have a ‘puppy coat’; skin darkens | Biopsy; eliminate other causes |
| 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 |
| Alopecia areata | Thought to be an autoimmune disorder | Patches of hair loss especially on head, neck, and body; no itching | Microscopic examination of hairs; biopsy |
| Atopy (allergic inhalant dermatitis) | Allergic reaction to something the dog inhales 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 |
| Bacterial infection (pyoderma)See Folliculitis | Often occurs as a result of another condition such as a parasitic, allergic, or hormonal condition | ||
| Black hair follicular dysplasia/alopecia/dystrophy | Rare hereditary disease in dogs with hair of multiple colors; more common in Bearded Collies, Basset Hounds, Salukis, Beagles, Dachshunds, and Pointers | Loss of dark or black hair only; symptoms appear between 3 and 6 weeks of age; sometimes scaling | Clinical signs, biopsy |
| Callus | Results from chronic pressure, especially in large breed dogs | Thickened, hairless raised areas over bony pressure points such as elbows; may become secondarily infected | History, clinical signs |
| Castration responsive dermatosis | More common in young unneutered dogs, and in Chows, Samoyeds, Keeshonden, Alaskan Malamutes, Miniature Poodles, and Pomeranians | Symmetrical hair loss in genital area and neck; hair loss may progress onto trunk; skin may appear darker; severe scaling; hair color may fade; coat is similar to a ‘puppy coat’ | Physical exam and history; eliminate other causes; blood tests forhormonelevels |
| Chemotherapy | Loss of hair due tochemotherapyis a concern for dog owners | Dogs with continuously growing hair, e.g., Poodles and Maltese, often lose some hair; dogs may lose whiskers | History |
| Cheyletiella (rabbit fur mite) mange | Infection with theCheyletiella mite | Itching, scaliness; some hair loss, if severe | Skin scraping and microscopic examination – the mite is often very difficult to find |
| Color dilution/mutant alopecia | Hereditary condition affecting dogs with blue (diluted black) or fawn coat colors; more common in Dobermans, Dachshunds, Great Danes, Yorkshire Terriers, Whippets, and Greyhounds | Hair in the blue- and fawn-colored areas starts to thin at around 6 months of age; secondary folliculitis often develops | Breed; history; and coat color |
| Congenital hypotrichosis | Congenital lack of hair | Puppies born with little or no hair; any hair they are born with is lost by 4 months of age | Physical exam; biopsy |
| Cushing’s disease (hyperadrenocorticism) | Caused by an increase in corticosteroids in the body – either due to increased production by the body or as a side effect of high doses or prolonged therapy withcorticosteroids | Hair loss, thinning of skin,hyperpigmentation, easy bruising, seborrhea, comedones (black heads), may see calcinosis cutis; lethargy, increased thirst and urination, potbellied appearance | Adrenal gland function tests, urinalysis, chemistry panel, CBC |
| Cyclic (cicatrical) alopecia; seasonal flank alopecia | Growth cycle of hair stops at certain times of the year | Symmetrical hair loss with definite borders; usually on back and flanks; skin may become darker | History, clinical signs, biopsy |
| Demodectic mange (red mange, puppy mange) |
Infection with theDemodex 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 |
| Dermatomyositis | Some breeds predisposed; cause unknown; aggravated by trauma and UV light | Redness, scaling,crusting, hair loss, and scarring on face, ears, and tail; atrophy of muscles involved in chewing | Skin biopsy |
| Diabetes mellitus | Abnormal immunity makes diabetic dogs susceptible to infection and other skin conditions | Thin skin; some hair loss; seborrhea; recurrent bacterial infections; unregulated dogs also have many other signs of disease; may develop epidermal metabolicnecrosis or xanthoma | Blood testing |
| Drug or injection reaction | Rare skin reaction to a drug which is inhaled, given orally, or appliedtopically; 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 |
| Epidermal metabolic necrosis (necrolytic migratory erythema, hepatocutaneous disease) | Uncommon skin disease in older dogs; skin lesions develop in dogs with certain diseases including liver disease, diabetes mellitus, and some pancreatictumors | Reddened, often ulcerated areas with hair loss and crusts; foot pads may be thickened | Biopsy; look for underlying disease |
| Erythema multiforme | Hypersensitivity reaction to infections or drugs; may also be caused bycancer or other diseases | Hair loss, ‘bull’s-eye’ lesions, andvesicles 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 |
| Estrogen responsive dermatosis (ovarian imbalance type II) | More common in young spayed dogs, and in Dachshunds and Boxers | Hair loss starting at the genital area and flanks and moving forward; hair color may fade; coat is similar to a ‘puppy coat’ | Physical exam and history; eliminate other causes; response to therapy |
| Flea allergy dermatitis (flea bite hypersensitivity) | Severe reaction by the animal to the saliva of the flea | Intense itching, redness, hair losspapules, crusts, and scales; sometimes development of infection or hot spots | Presence of fleas; reaction tointradermal testing |
| Follicular dystrophy/alopecia/dysplasia (abnormal development or growth of hair)See Congenital hypotrichosis, Color dilution/mutant alopecia, Black hair folliclular dystrophy/alopecia, Follicular dysplasia (non-color linked) | May be congenital (certain breeds are at increased risk) or acquired later in life from infections, hormonal abnormalities,cancer drugs, and some other diseases | Hair loss, sometimes only hair of a certain color; sometimes scaling | Clinical signs, breed, skin biopsy |
| Follicular dystrophy/dysplasia (non-color linked) | Patchy hair loss of unknown cause seen in the Siberian Husky, Doberman Pinscher, Airedale, Boxer, Staffordshire Bull Terrier, Curly Coated Retriever, Irish Water Spaniel, and Portuguese Water Dog | In Huskies, hair loss on the body, reddish tinge to hair; in Dobermans, hair loss over lumbar area; in Boxers and Terriers, hair loss over lumbar area, skin may behyperpigmented; in the Retrievers and Spaniels, loss of guard hairs on back and trunk and secondary hairs are dull and lighter in color | Breed, biopsy |
| Folliculitis | Infection of the hair follicles, often with staph bacteria; symptoms usually appear on skin with less hair, such as the abdomen | Pustules form in follicles and break open to form ‘bull’s-eye,’ ‘annular,’ and ‘target lesions,’ which have crustycenters and red or darkening on the periphery, and ‘epidermal collarettes,’ which appear as rings ofscaly skin; may itch; short-coated breeds may develop small tufts of hair, which are lost; breeds with long coats may have seborrhea | Skin scraping; culture; biopsy |
| 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 |
| 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 nodulesof varying sizes; those due to foreign bodies often have draining tracts; may develop hair loss,ulcers, andsecondary infections | History, clinical signs, biopsy, surgical exploratory |
| Growth hormone responsive alopecia | Not well understood; thought to be caused by an enzyme deficiency or decrease of adrenalhormones, which allows certain other hormones to accumulate in the body: more common in Pomeranians, Chow Chows, Keeshonden, Samoyeds, and Poodles | Hair loss on neck, tail, and the back of the thighs; skin darkens; usually starts when dog is less than two years old | Hormonal blood testing |
| Hair loss during pregnancy and nursing (‘blowing her coat,’telogen effluvium) | Excess shedding that can also occur in other stressful circumstances such as illness or surgery | Sudden and widespread hair loss | History, clinical signs |
| Histiocytosis | There are several kinds of histiocytosis:malignant, which is a cancerthat affects the skin and internal organs; systemic, which is a rare disease which affects skin and internal organs; and cutaneous, which is abenign disease affecting the skin | All cause noduleswith hair loss; malignant and systemic also haveulcers | Biopsy, fine needle aspirate; |
| Hyperestrogenism (ovarian imbalance type I) | Rare disease in which female animals have excess levels of estrogen; can be caused by cancerof the ovaries | Symmetrical loss of hair; hair pulls out easily; darkening of the skin; enlarged nipples and vulva; may rarely see seborrhea and itching | History, physical exam, rule out other causes of hair loss, measure blood estrogen levels |
| Hypothyroidism | Decreased production of thyroidhormone; most common hormonal disease affecting the skin in dogs | Hair loss, dry and brittle hair, seborrhea; secondary bacterial and yeast infections; lethargy, obesity, slow heart rate; changes in skin pigmentation may occur | Thyroid gland function tests, chemistry panel, CBC |
| Injection site alopecia | Hair loss at the site of an injection of a medication or vaccine; skin may become thickened; in cats, ulcers may develop | Hair loss occurs several months after injection; area may becomehyperpigmented | History and physical examination |
| Interstitial cell tumor | Tumor of the testicle; may not cause any skin changes | If skin changes occur, see seborrhea, loss of hair on the trunk, enlargement of the tail gland and perianal glands; may see increased pigment in the skin | Biopsy |
| Kerion | Complication of ringworm infection | Nodule with hair loss and multiple draining tracts; may not see other signs of ringworm | Culture, biopsy |
| Leishmaniasis | Caused by a parasite of blood cells; can be transmitted to people who develop a very severe disease | Hair loss, scaling,ulcers on nose and ears, sometimesnodules; many other nonskin-related signs | Identify the organism in blood or biopsy; blood tests |
| Lice | Infection with several species of lice | Variable; itching, hair loss, crusts, rough hair coat | Finding lice or nits on skin or hair |
| Malassezia | Usually follows some other underlying disease | Itching, redness, hair loss, greasyscales; if chronic, develophyperpigmentation | Skin scraping/smear and microscopic examination, culture |
| Nasal solar dermatitisSee solar dermatitis | See solar dermatitis | ||
| Pattern alopecia (pattern baldness) | Three types; hair loss may occur on the ears of Dachshunds (pinnal alopecia); neck, thighs, and tail of American Water Spaniels and Portuguese Water Dogs; abdomen and the back of the thighs of Dachshunds, Chihuahuas, Whippets, and Greyhounds | Hair loss in described areas | Breed, history, biopsy |
| 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, and scales | Skin scraping and microscopic examination |
| Pituitary dwarfism | Hereditary condition in which the pituitary gland does not produce the necessaryhormones | Young puppies fail to grow; dogs retain puppy coat and condition progresses to hair loss over much of the body; thin skin,scales, andsecondary infections | Special blood testing for the presence of certain hormones |
| Post-clipping alopecia | Hair may not grow back immediately after it has been clipped; which animals may be affected can not be predicted; more common in dogs with thick undercoats e.g., Huskies and Chows | Continued lack of growth in hair that was clipped, e.g., for surgery | History |
| Pressure sores (decubital ulcers) | Lesions occur over bony prominences like elbows; common in larger recumbent dogs | Start as red, hairless areas and progress to draining ulcers; may become infected | Clinical signs, biopsy |
| Pyoderma-superficial(See Folliculitis) | |||
| Ringworm | Infection with several types of fungus | Hair loss, scaliness,crusty areas,pustules, vesicles, some itching; can develop a drainingnodule called a ‘kerion’ | Culture |
| Sarcoptic mange | Infection with theSarcoptes 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 |
| Schnauzer comedo syndrome | Uncommon; only seen in Miniature Schnauzers | Comedones (black heads) on back, mild itching; may seesecondary infection, thinning of hair; small crusts may develop | Clinical signs, breed, skin biopsy |
| 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 |
| 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 scrapings, etc., to find underlying cause |
| Sertoli cell tumor | Tumor of the testicles in middle-aged dogs | Male dogs take on female sexual characteristics; hair loss, increased skin pigment, reddened area on prepuce | Physical exam |
| Solar dermatosis | Skin reaction to sunlight, especially unpigmented skin; most common on the noses of Collies, Shelties, and similar breeds | Redness, hair loss, and scaling on nose and ears, latercrusts and ulcers | History, breed, physical exam, skin biopsy |
| Tail dock neuroma | Nerve regrowth after tail docking causes symptoms | Nodule at site of docking, itching with self-mutilation, hair loss, andhyperpigmentation | History and symptoms |
| Tail gland hyperplasia | Dogs have asebaceous gland on the top of the tail near its base; in this disorder, the gland enlarges; seen in unneutered dogs and secondary to other diseases such as hypothyroidism | Oily area, hair loss,crusts, andhyperpigmentationon area over gland | Clinical signs; look for underlying cause |
| Testosterone responsive dermatosis (hypoandrogenism) | More common in old neutered dogs, and in Afghans | Dull, scaly, dry coat; seborrhea; hair loss in genital and anal areas progressing onto trunk | Physical exam and history; eliminate other causes; response to therapy |
| Vitamin A responsive dermatosis | May not be due to an actual deficiency of Vitamin A, but does respond to increased levels of Vitamin A in the diet; more common in Cocker Spaniels | Seborrhea; odor; hair pulls out easily; pads of feet thickened; thickscales on chest and abdomen, especially around nipples | Clinical signs, breed, skin biopsy |
| Zinc responsive dermatosis | Three types: I in Huskies and Malamutes; II in rapidly growing puppies of large breeds; III in English Bull Terriers | Crusting and scaling, redness, hair loss, sometimes oily skin, secondary bacterial infections common | History, breed, physical exam, skin biopsy |