This page serves as an introduction and suggest where to look to find the cause of a problem.
The itchy skin diseases in the first part are characterized by constant scratching, biting at the skin, and rubbing up against objects to relieve the itch.
The next two parts list diseases characterized by hair loss with few if any other signs. Hair loss can mean impaired growth of new hair. It may involve the entire coat, or you may see patches of hair loss on certain parts of the body. In general, hair loss caused by hormonal diseases is symmetric (the same on both sides of the body), while that caused by parasites and other causes is asymmetric.
The fourth part lists diseases in which the predominant sign is skin infection or pyoderma. Pyoderma is characterized by pus, infected sores, scabs, ulcers of the skin, papules, pustules, furuncles, boils, and skin abscesses. The skin infection is often secondary to some other skin disease, particularly an itchy skin disease that causes the dog to attack her own skin.
The part after that lists autoimmune and immune-mediated skin diseases, characterized by blebs. Blebs, also called vesicles, are blisters that contain clear fluid. Large ones are called bullae. All tend to progress through rubbing, biting, and scratching, eventually producing skin erosions, ulcers, and crusts. Look for these changes to appear first on the face, nose, muzzle, and ears.
During the course of grooming, playing with, or handling your dog, you may discover a lump or bump on or beneath the skin. To learn what it may be, see the last part on lumps or bumps on or beneath the skin. Tumors and Cancers, contains more information on this.
Itchy Skin Diseases in dogs
Allergic contact dermatitis: Same as contact dermatitis, but rash may spread beyond the area of contact. Requires repeated or continuous exposure to allergen (such as wearing a flea collar).
Canine atopy: Severe itching that occurs in young dogs and begins in late summer and fall. Caused by seasonal pollens. Occurs in mixed breeds as well as purebreds. Common. Tends to get worse each year. May start with face rubbing and foot chewing.
Chiggers: Itching and severe skin irritation between the toes and around the ears and mouth. Look for barely visible red, yellow, or orange chiggers.
Contact dermatitis: Red, itchy bumps and inflamed skin at the site of contact with a chemical, detergent, paint. or other irritant. Primarily affects feet and hairless parts of the body. Can also be caused by rubber or plastic food dishes, with hair loss on the nose.
Damp hay itch (pelodera): Red pimplelike bumps on skin. Severe itching. Occurs in dogs bedded on damp hay and similar grass. Caused by a parasite.
Flea allergy dermatitis: Red, itchy pimplelike bumps over the base of the tail, back of rear legs, and inner thighs. Scratching continues after fleas have been killed.
Fleas: Itching and scratching along the back, and around the tail and hindquarters. Look for fleas, or black and white gritty specks in hair (flea feces and eggs).
Fly-bite dermatitis: Painful bites at tips of erect ears and bent surfaces of floppy ears. Bites become scabbed and crusty black, and bleed easily.
Food allergy dermatitis: Nonseasonal itching with reddened skin, papules, pustules, and wheals. Found over the ears, rump, back of the legs, and undersurface of the body. Sometimes confined just to the ears with moist, weeping redness.
Grubs/Cuterebra: Inch-long fly larvae that form cystlike lumps beneath the skin with a hole in the center for the insect to breathe. Often found beneath the chin, by the ears, or along the abdomen.
Lice: Two-millimeter-long insects, or white grains of “sand” (nits) attached to the hair. Not common. Found in dogs with matted coats. May have bare spots where hair has been rubbed off.
Lick granuloma (acral pruritic dermatitis): Red, shiny skin ulcer caused by continuous licking at wrist or ankle. Mainly in large, short-coated breeds.
Maggots: Soft-bodied, legless fly larvae found in damp matted fur or wounds that aren’t kept clean.
Scabies (sarcoptic mange): Intense itching. Small red spots that look like insect bites on the skin of the ears, elbows, and hocks. Typical crusty ear tips.
Ticks: Large or very small insects attached to the skin. May swell up to the size of a pea. Found beneath the ear flaps and where hair is thin. May or may not induce itching.
Walking dandruff (cheyletiella mange): Occurs in puppies 2 to 12 weeks of age. Large amounts of dry, scaly, flaky skin over the neck and back. Itching is variable.
Hormone-Related Diseases with Hair Loss in dogs
Cortisone excess: Symmetric hair loss over trunk and body. Abdomen is pot-bellied and pendulous. Seen with Cushing’s syndrome. In some cases, the dog is taking steroids.
Growth hormone-responsive alopecia: Bilaterally symmetric hair loss, mainly in male dogs. Begins around puberty. More prevalent in certain breeds, including Chow Chows, Keeshonds, Pomeranians, Miniature Poodles, Airedales, and Boxers.
Hyperestrogenism (estrogen excess): Occurs in females and males. Bilateral symmetric hair loss in perineum and around genitals. Enlarged vulva and clitoris; in males, pendulous prepuce.
Hypoestrogenism (estrogen deficiency): Occurs in older spayed females. Scanty hair growth and thinning coat, initially around vulva and later over entire body. Skin is smooth and soft, like a baby’s.
Hypothyroidism: Most common cause of bilaterally symmetric hair loss without itching. Coat is thin, scanty, and falls out easily. Involves the neck beneath the chin to the brisket, sides of body, backs of thighs, and top of tail.
Other Diseases with Hair Loss in dogs
Acanthosis nigrans: Mainly in Dachshunds. Hair loss begins in armpit folds and on ears. Black, thick, greasy, rancid-smelling skin.
Color mutant alopecia (blue Doberman syndrome): Loss of hair over the body, giving a moth-eaten look. Papules and pustules may appear in areas of hair loss. Also affects other breeds.
Demodectic mange: Localized—Occurs in puppies. Hair loss around eyelids, lips, and corners of mouth, occasionally on the legs or trunk, giving a moth-eaten look. Fewer than five patches, up to 1 inch (25 mm) in diameter. Generalized—Numerous patches that enlarge and coalesce. Severe skin problem complicated by pyoderma. Primarily affects young adults. Generalized form is associated with immune deficiencies.
Nasal solar dermatitis (Collie nose): Loss of hair at junction of nose and muzzle. Can lead to severe ulceration. Affects dogs with lightly pigmented noses. May be part of an autoimmune problem.
Pressure sore (Callus): Gray, hairless, thickened pad of wrinkled skin, usually over elbows but may involve other pressure points. Caused by lying on hard surfaces. Mostly seen in large and giant breeds.
Ringworm: A fungal infection. Scaly, crusty circular patches 1⁄2 to 2 inches (12 to 50 mm) across. Patches show central hair loss with a red ring at the periphery. Some cases show widespread involvement.
Sebaceous adenitis: Seen mainly in Standard Poodles, but does occur in other breeds, including Akitas. Symmetrical loss of hair over face, head, neck, and back. Dandrufflike scales and hair follicle infection can develop.
Seborrhea: Dry type—Similar to heavy dandruff. Greasy type—Yellow-brown greasy scales that adhere to hair shafts; rancid odor. May occur secondary to other skin problems.
Vitiligo: Some hair loss, but mostly pigment loss that causes hair to change color. Mostly seen on the face and head. Seen most often in Rottweilers and Belgian Tervuren.
Zinc-responsive dermatosis: Crusty, scaly skin with hair loss over the face, nose, elbows, and hocks. Cracked feet. Caused by zinc deficiency. Arctic or Northern breeds are most susceptible.
Skin Diseases with Pus Drainage
Actinomycosis and nocardiosis: Uncommon skin infections with abscesses and draining sinus tracts that discharge pus and respond slowly to treatment.
Acute moist dermatitis (hot spots): Rapidly advancing patches of inflamed skin from which the hair falls out. The skin is covered with a wet exudate of pus. Progresses through self-chewing and results in pyoderma. Often occurs under ear flaps of dogs with drop ears, such as Newfoundlands and Golden Retrievers. May be associated with an underlying skin disease, but can also occur in hot, humid weather if dogs swim or are bathed and don’t dry thoroughly.
Cellulitis or abscess: Painful, warm, reddened skin or pockets of pus beneath the skin. Look for a cause, such as a foreign body, bite wound, or self-trauma from irrita- tive skin disease.
Folliculitis (hair pore infection): Hair shaft protrudes through the center of a pus- tule. Superficial—Similar to impetigo, but extends to involve armpit folds and chest. Deep—Pustules become larger and firmer. Pus, crusts, and draining tracts in the skin.
Impetigo: Pustules and thin brown crust on hairless skin of abdomen and groin. Occurs in young puppies. May also be called puppy acne.
Interdigital cysts: A swelling between the toes that may open and drain pus.
Mycetoma: Painful swelling at the site of a puncture wound, usually on the legs or feet. Pus drains through sinus tracts deep in the mass. Usually caused by a fungus, but can be bacterial.
Puppy acne: Purplish red bumps on the chin and lower lip. Not painful. Also called impetigo.
Puppy strangles (juvenile pyoderma): Painful swelling of the face (lips, eyelids, ears), followed by rapid appearance of pustules and draining sores. Swollen lymph nodes around the head and neck. Occurs in puppies under 4 months of age.
Skin fold pyoderma (skin wrinkle infection): Red, inflamed skin with a foul odor in a lip fold, nose fold, vulvar fold, or tail fold.
Autoimmune and Immune-Mediated Skin Diseases in dogs
Bullous pemphigoid: Similar to pemphigus vulgaris, but usually begins at the junc- tion of the skin and the mucous membranes. The mouth is commonly involved.
Discoid lupus erythematosus: Affects the flat surface of the nose. Ulceration and depigmentation are characteristic.
Erythema multiforme: Acute eruption of the skin and mucous membranes. Often caused by drugs. Characteristic targetlike eruptions with red rims and blanching at the center.
Pemphigus erythematosus: Similar to pemphigus foliaceus, but restricted to the face, head, and foot pads.
Pemphigus foliaceus: Red skin patches (macules) that progress rapidly to pustules and then to dry yellow crusts. Usually limited to the face (nose, muzzle, around the eyes and ears). Crusts adhere to underlying skin and hair. Often becomes generalized. Depigmentation seen in late stages. The feet can become thickened and cracked. Occasionally only the foot pads are involved.
Pemphigus vegetans: Flat-topped pustules involving skin folds. Heals with wartlike growths.
Pemphigus vulgaris: Vesicles and bullae that ulcerate and form thick crusts. Usually found around the lips and in the mouth, but may be generalized. Ulceration of foot pads and shedding of nails are common.
Nodular panniculitis: Multiple lumps (like marbles beneath the skin) over the back and along the sides. Lumps open and drain, then heal by scarring.
Systemic lupus erythematosus: Skin involvement similar to pemphigus foliaceus. First sign may be wandering lameness. Ulceration of foot pads is common.
Toxic epidermal necrolysis: Severe, painful skin disease. Blebs and ulcers involve the skin, mucous membranes, and foot pads. Large sections of skin are shed as in a burn injury.
Lumps and Bumps on or Beneath the Skin in dogs
Abscess: A painful collection of pus at the site of a bite or puncture wound.
Basal cell tumor: Solitary nodule, usually on a narrow base or stalk. Round, normally hairless, and may be ulcerated. Found on the head, neck, and shoulders of older dogs.
Ceruminous gland adenoma: A pinkish-white dome-shaped growth in the ear canal less than 1 centimeter in size. May become ulcerated and infected.
Epidermal inclusion cyst: A firm lump beneath the skin. May discharge cheesy material and become infected.
Hematoma: A collection of clotted blood beneath the skin; often involves the ear flaps.
Histiocytoma: Rapidly growing dome-shaped (buttonlike) growth found anywhere
on the body, usually in young adults.
Lipoma: Smooth round or oblong growth beneath the skin; feels somewhat soft.
Mast cell tumor: Solitary or multiple growths usually found on the trunk, perineum, and legs. More prevalent in certain breeds, including Boxers, Golden Retrievers, Bulldogs, and Boston Terriers.
Melanoma: A brown or black pigmented nodule found in areas of dark skin. Growths in mouth and nailbeds usually are malignant.
Perianal gland tumor: A solitary or multinodular growth in the perineum around the anus. Occurs most often in older intact males.
Sebaceous adenoma: Also called sebaceous cyst. Smooth, pink, wartlike growth less than 1 inch (2.5 cm) in diameter. Most common on the eyelids and limbs. Occurs in older individuals (average age 10). Very common in Poodles and Cocker Spaniels.
Skin papillomas: These grow out from the skin and may look like a wart. Not painful or dangerous
Soft-tissue sarcomas: Ill-defined or well-demarcated masses of varying size and location. Often slow growing.
Squamous cell carcinoma: A nonhealing gray or reddish-looking ulcer found on the belly, scrotum, feet, legs, lips, or nose. May resemble a cauliflowerlike growth.
Transmissible venereal tumors: Ulcerated, often multiple cauliflower-like growths on the genitalia of both sexes.