Skin Diseases in Dogs
BACTERIAL SKIN INFECTIONS
(PYODERMAS)Causes
– Staphylococci (‘Staph bacteria’) are the most
common organisms found in bacterial skin diseases (pyoderma’s) in dogs.
Fortunately, these bacteria (S. intermedius) are not contagious to humans or
other pets.Signs
– Commonly itchy, yellow pustules are often observed
early in the disease, and the dog’s skin can be reddened and ulcerated. Dry,
crusted areas appear as the condition advances, along with loss of hair in the
affected areas (lesions) and an odour.
All areas of a dog’s body may be
involved, but most cases are confined to the trunk. The chin is one area
commonly affected. Called chin acne, this condition is actually a deep bacterial
infection. Obese dogs and dogs of the pug-nosed breeds are frequently affected
by pyoderma in the skin folds on their face, lips and vulva.
Other areas
where pyoderma may occur include between the toes and on the calluses of the
elbows that mostly affects the abdominal area in young puppies.
Diagnosis
– This is usually made from the case history and appearance
and location of the lesions. In some cases, it may be necessary to culture the
skin (grow the bacteria) and conduct sensitivity tests to determine which
antibiotic will be effective in treatment. Most bacterial skin infections in
dogs are secondary to another disease such as parasitism, allergies, endocrine
(hormonal) disorders or abnormalities in the immune system. Therefore, in
recurrent cases, it is important to search for underlying causes. It may be
necessary to do blood tests, allergy tests or skin biopsies to achieve a
complete diagnosis.
Treatment
– Initial treatments may entail removal
of the hair in and around the lesions, washing of the whole dog with antibiotic
shampoos such as benzoyl peroxide, careful drying and the application of an
antibiotic ointment to local lesions, in most cases, antibiotics will also be
administered orally for 3-4 weeks. Bandages or a protective collar which
prevents the dog from mutilating the lesions may be applied.
Some pyoderma
involving skin folds can require corrective surgery. In recurrent cases where
testing reveals no definable underlying cause, special staphylococcal vaccines
as an alternative to long-term antibiotic treatment can be tried.
It may
be necessary to continue treatments such as antiseptic shampooing, antibiotic
ointment applications and giving antibiotics orally at home. While most cases
respond to treatment, recurrences of pyoderma are common, particularly if
treatment recommendations and follow-up visits to your veterinarian are
neglected. Glucocorticoid steroids cannot be administered.
Fungal Skin Infections (Ringworm)
Cause
– The
fungal skin infections of dogs are caused primarily be two species of fungi:
Microsporum and Trichophyton. The skin diseases resulting from these fungi are
commonly called ‘ringworm.’
Signs
– Ringworm is seen most commonly in
young dogs. The fungi live in dead skin tissues, hairs and nails. Hair loss,
usually in circular patches, may appear. If infected, the center of the patches
may have a dry, crusty appearance. The head and legs are most commonly affected
by ringworm, although the disease may spread over other parts of the dog’s body
if not treated. Dogs may scratch the lesions.
Diagnosis
– The
appearance of the lesions, the history of their development and the age of the
dog are all helpful in diagnosing ringworm. A Wood’s Lamp Test (ultraviolet
light) can be used to help diagnose the Microsporum species only. A definite
diagnosis can be obtained through a fungal culture — grow the fungi found on
the affected hairs.
Treatment
– The hair around the lesions is
clipped, and special fungicidal shampoos or rinses are used for bathing the dog.
Topical lime sulfur and mandatory systemics should be administered.
Public Health Aspects of Ringworm – Ringworm is contagious to humans,
particularly to children and to other household pets. Infected dogs should be
kept away from children and other dogs and cats until the infection is cures –
which can be as long as 2-3 months or more after the treatment begins. Adults
should be careful to wash their hands thoroughly after handling an infected dog.
If treated early, ringworm is readily controlled in humans. Other household pets
should also be examined for ringworm.
Allergic Skin
Diseases
Allergies in dogs are common. Signs such as itchy skin,
nasal and eye discharges and sneezing, and/or digestive upsets and/or skin
lesions may indicate an allergy is present. Many skin diseases seen in dogs are
caused by an allergy.
Causes
– An allergy is a hypersensitivity
reaction to allergy-causing substances known as ‘allergens’ or ‘antigens.’ Dogs
(like people) can develop allergies at any age, and the signs can appear quite
suddenly.
The most common allergy dogs develop is the flea saliva. The
presence of a single flea on these allergic dogs causes intense itching. These
allergies are seasonal in climate zones where fleas are eliminated by the cold
in winter months — and a year-round problem in warmer climates.
Atopy
(atopic dermatitis, allergic inhalant dermatitis) is a pruritic (itchy) skin
disease dogs develop in response to inhaled particles such as house dust, molds
and pollens. This common form of allergy usually starts at a relatively young
age. Rarely, dogs can be allergic to chemicals contained in soaps, waxes,
carpets and flea collars. This type of hypersensitivity is known as a ‘contact
allergy.’ Also, some dogs are allergic to insect bites and stings. Food
allergies usually case diarrhea and/or skin lesions.
Signs
– Itching
is the primary sign of allergic skin diseases in dogs. The affected skin may
appear normal, or red and moist in patches called ‘hot spots.’ Pus and dried
crusts are apparent if a bacterial infection is also present. The dog tends to
constantly scratch and lick affected areas. Initially, flea allergies are most
evident over the dog’s back and near the tail. A dog’s face, feet, chest, and
abdomen are more often affected by pollen and dust-type allergies. Contact
allergies are seen mostly on the hairless areas of the abdomen and on the
bottoms of the feet.
Diagnosis
– The dog’s case history helps with
the diagnosis. The intense itching and location of the lesions are also helpful
in diagnosing the type of allergy present. Response to treatment (flea control)
is often used as a method of diagnosis of flea allergy. Trials of special
hypoallergenic diets are used to diagnose food allergy. Allergy testing is used
to help choose immunotherapy. Blood tests are also available to diagnose
allergies, but their use is more controversial. Ask your veterinarian for his or
her current recommendations.
Treatment
– Allergies can be controlled
in most cases, with few ‘cured.’ Antihistamines and corticosteroids may be used
by your veterinarian to give your dog relief from the intense itching. In most
cases this will stop the self-mutilation. The owner will be instructed to give
corticosteroid tablets in decreasing dosages for a few months. Corticosteroids
are potent drugs and should not be used carelessly or for long periods of time.
The main objective in controlling flea allergies in dogs is to kill the fleas on
the dog and in the dog’s environment.
Another approach to allergy control is
hyposensitization (immunotherapy). In this procedure, a correct diagnosis by
intradermal or blood testing is necessary. The dog is then given injections of
small but increasing doses of the allergy-causing substance at varying intervals
for up to 12 months. Lifelong response may take up to 12 months.
Parasitic Skin Diseases
Cause
– Fleas are the
most common parasitic skin disease found in dogs. Mange is another type of skin
disease which is caused by mites. There are two severe types of mange: sarcoptic
mange and demodectic mange.
- Ear mites, lice, and ticks are other
parasites that affect dogs. Their presence irritates the dog, leading to
self-mutilation.
Signs
– Sarcoptic mange causes intense itching, loss
of hair and crusting of the skin. A dog’s ears, front legs, chest and abdomen
are most often affected by sarcoptic mange.
- Demodectic mange can cause
itching. The skin is reddened and scaly, and hair loss occurs in round patches
resembling ‘ringworm.’ The face and front legs are most commonly affected,
although some cases may be generalized. Generalized demodectic mange is often a
sign of underlying internal disease or a hereditary problem.
- Ear mites
cause severe irritation in the ears. Often, an affected dog will scratch the
hair off the back of its ears. Ticks, lice and fleas may transmit other
diseases, in addition to causing irritation.
Diagnosis
– Mange is
often suspected on the basis of the case history and the appearance and location
of the lesions. A skin scraping test is always performed to aid in identifying
parasites. Ear mites, which are barely visible to the naked eye, appear as small
white objects. The black debris commonly seen in the ears of dogs with ear mites
is a combination of dried blood, normal ear wax and discharges from
inflammation. Lice, fleas and ticks can also be seen by close examination of the
dog’s skin.
Treatment
– Mange is treated by clipping the affected
areas and washing them with an antiseptic. Antimite dips are often necessary and
may be used weekly or biweekly for several months. Shampoos can be sued before
each dip. The dog’s eyes should be protected with mineral oil or eye ointment
and the ears plugged with cotton before dipping. Most cases of mange respond
well to this treatment. Antibiotics can be administered in cases of mange where
infection may be present.
Ear mites can be readily treated Initially,
your veterinarian may recommend a thorough cleaning of the dog’s ears while the
animal is sedated. This treatment can be followed up with home treatments using
special solutions or ointments to kill the mites and prevent infections in
addition, insecticidal dips, sprays, powders or shampoos are often used.
Lice, ticks and fleas must be killed on the dog and in the dog’s
environment with insecticides. Dips, shampoos, flea collars, sprays, powders,
foams and foggers containing insecticides are available from your veterinarian
to help control these parasites.
Hormonal Skin
Diseases
Skin diseases caused by hormonal abnormalities in dogs are
difficult to diagnose. The thyroid gland, adrenal glands, pituitary gland,
testicles and ovaries all produce hormones. If excessive (‘hyper’) or deficient
(‘hypo’), these hormones produce changes in the skin and hair coat. Most
hormonal problems that affect the skin produce hair loss that is evenly
distributed on each side of the dog’s body. The skin may be thicker or thinner
than normal, and there may be changes in the color of the skin or hair coat.
These diseases usually are not itchy.
When any of the hormone-producing
glands malfunction, they affect other body functions besides the skin. Hormonal
skin diseases in dogs can be much more serious than a ‘skin problem.’
Some causes of hormonal skin disease, such as hypothyroidism and adrenal
gland problems, can be diagnosed by special blood tests and effectively treated.
Others may be more difficult to diagnose and treat. Skin changes related to the
sex hormones can be successfully treated with surgical neutering, if this has
not been performed previously.
Condition : Atopy
(Allergic Inhalant Dermatitis)
Description : Allergic reaction by the
animal to something it inhales such as pollen, house dust mites and
mould
Symptoms : Licking of feet, inflamed ears, itching, redness,
sometimes development of infection or hot spots
Diagnosis :
Intradermal or serologic (blood) testing for allergies
Treatment :
Reduce exposure to allergen (what the pet is allergic to), shampoos, fatty
acid supplements, steroids, antihistamines,
immunotherapy
Condition : Food Allergies
Description :
Allergic reaction to something in the diet
Symptoms : Licking of
feet, inflamed ears, itching, redness, sometimes development of infection or hot
spots
Diagnosis : Food elimination trials
Treatment : Change
in diet
Condition : Allergic and Irritant (Contact
Dermatitis)
Description : Reaction of the pet’s skin to something it
had contact with such as wool or plastics
Symptoms : Red skin and
small bumps or blisters on the areas of skin that are sparsely haired and
directly exposed to the offending substance, itching
Diagnosis : Patch
test, exclusion trials
Treatment : Restrict exposure to the allergen
or contact irritant in the pet’s environment, steroids,
antihistamines
Condition : Flea Allergy Dermatitis (Flea
Bite Hypersensitivity)
Description : Severe reaction by the animal to
the saliva of the flea
Symptoms : Intense itching, redness, hair loss;
sometimes development of infection or hot spots
Diagnosis : Presence
of fleas; reaction to intradermal testing
Treatment : Flea Control in
the environment and on the pet; steroids and antihistamines for the
itching
Condition : Sarcoptic Mange
Description
: Infection with the Sarcoptes mite
Symptoms : Intense itching and
self-trauma
Diagnosis : Skin scraping and microscopic examination -
the mite is often very difficult to find
Treatment : Amitraz (Mitaban)
dips (off-label use*); ivermectin (off-label
use*)
Condition : Demodectic Mange in Dogs (Red
Mange)
Description : Infection with the Demodex mite – occurs when the
immune system is deficient
Symptoms : Hair loss, scaliness, redness,
pustules, ulcers, sometimes itching
Diagnosis : Skin scraping and
microscopic examination
NO Steroids!
Treatment : Amitraz (Mitaban)
dips
Condition : Cheyletiella (Rabbit Fur Mite)
Mange
Description : Infection with the Cheyletiella
mite
Symptoms : Itching, scaliness
Diagnosis : Skin scraping
and microscopic examination – the mite is often very difficult to
find
Treatment : Permethrin (Dogs ONLY) or
Pyrethrin
Condition : Ringworm
Description :
Infection with several types of fungus
Symptoms : Hair loss,
scaliness, crusty areas, some itching
Diagnosis :
Culture
Treatment : Miconazole, lime sulfur dips; oral
griseofulvin or itraconazole
Condition : Yeast
Infection
Description : Infection with, most commonly, Malassezia;
usually follows some other underlying disease
Symptoms : Itching,
redness, sometimes oiliness
Diagnosis : Skin scraping/smear and
microscopic examination, culture
Treatment : Treat underlying disease;
oral ketoconazole; miconazole shampoos
Condition : Hot
Spots: Acute Moist Dermatitis
Description : Result from allergies,
flea bites, mange, anal gland disease, poor grooming, ear infections, plant awns
or burs, arthritis
Symptoms : Hair loss; red, moist, oozing skin;
constant licking or scratching
Diagnosis : Physical exam and
history
Treatment : Treat underlying condition; clean area; apply
Domeboro solution; topical and/or oral antibiotics and
steroids
Condition : Cutaneous
Lymphoma
Description : Rare type of skin cancer
Symptoms :
Itching, ulcers, nodules, redness
Diagnosis :
Biopsy
Treatment : Usually does not respond to
treatment
Condition : Lice
Description :
Infection with several species of lice
Symptoms : Variable;
itching, hair loss, crusts, rough hair coat
Diagnosis : Finding lice
or nits on skin or hair
Treatment : Permethrin (Dogs ONLY) or
Pyrethrin, ivermectin (off-label use*)
Condition :
Skin Fold Dermatitis
Description : Occurs where folds of skin touch
each other such as lips, vulva, face (in breeds like bulldogs)
Symptoms :
Redness, oozing, itching
Diagnosis : Physical exam;
microscopically examine smear for evidence of infection
Treatment :
Treat any infections; clean areas daily; surgical correction if
severe
Condition : Hookworms
Description :
Infection with the larvae (immature forms) of hookworms
Symptoms :
Red bumps, usually on feet, rough foot pads, abnormal nail growth,
itching
Diagnosis : Physical exam, history of poor
sanitation
Treatment : Treat for intestinal infection; move animal to
different environment
Condition :
Neurodermatitis:
Acral Lick Dermatitis
(Dogs)
Psychogenic
Dermatitis
(Cats)
Description : Self-licking in dogs and cats
results in self-trauma; possible causes include anxiety, boredom, stress (e.g.,
new member in household)
Symptoms : Acral Lick: red, hairless,
well-circumscribed lesion usually on forearm; cats: symmetrical hair loss,
sometimes ulcers, on abdomen, groin, along the back
Diagnosis :
Exclude other causes; history important
Treatment : Relieve
underlying cause e.g., anxiety;
Condition : Bacterial
Infection
Description : Often occurs as a result of another
condition
Symptoms : Redness, pustules, bumps, sometimes
itching
Diagnosis : Microscopic examination of smear;
culture
Treatment : Treat underlying condition; topical and/or oral
antibiotics
Condition : Ear Mites
Description :
Infection with Otodectes
Symptoms : Intense itching of ears,
redness, dark crumbly discharge in ears
Diagnosis : Direct visual or
microscopic examination of ear discharge
Treatment : Clean ears and
apply medication containing pyrethrin (Ear
Miticide)
Condition : Pelodera
Dermatitis
Description : Accidental infection with larvae from a
non-parasitic worm that lives in straw and other organic material
Symptoms
: Intense itching, redness
Diagnosis : Skin scraping and
microscopic examination
Treatment : Remove bedding; mild antibacterial
shampoo; steroids if necessary to control
itching
Condition : Chiggers (Harvest
mites)
Description : Seasonal disease caused by larvae of the
chigger
Symptoms : Itching, bumps usually on feet, abdomen, folds at
base of ears
Diagnosis : Visualization of mite larvae or microscopic
examination of skin scraping
Treatment : Permethrin (Dogs ONLY) or
Pyrethrin
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