Dog Bacterial Skin Infections [With Pictures & Vet Advice]

Canine skin disease is a common problem that can affect any breed. Most dog lovers have had some experience caring for dogs with red, itchy skin. While all dogs are vulnerable to canine skin disease, some breeds are more susceptible.

For example, Shar Peis and French Bulldogs are prone to infections in their skin folds. Labradors and Golden Retrievers attract hot spots, while Basset hounds are prime real estate for yeast and bacterial growth.  Dermatological problems can be very frustrating. Not only is your pooch uncomfortable, but the necessary treatments can often be prolonged.

Working as a veterinary technician in a busy veterinary hospital, I’ve treated many dogs suffering from itchy, painful skin. From what I have seen, the surest path to resolving the problem is to obtain an accurate diagnosis right from the start.   

Symptoms of bacterial skin disease

The majority of canine skin infections are bacterial. They are usually secondary to another disease process. Here are some of the main symptoms to watch out for that many indicate bacterial skin infection (also known as pyodermas):

1. Redness, pustules, or papules
2. Crusty lesions or flaky skin
3. Swelling, oozing or draining of a blood-tinged fluid or pus
4. Small red bumps

The picture below shows a red, circular lesion that is quite inflamed (staphylococcus bacterial infection). This is sometimes called a ‘bullseye’ lesion:

With bacterial infections, there is usually inflammation of the hair follicle called folliculitis. This can lead to the build-up of crusts (scabs form). There may be small bumps (papules), raised hairs (tufted papules) and hair loss. Learn more about Folliculitis.

The picture below shows several pustules and inflamed red skin from a bacterial skin infection.

Skin infections can lead to skin irritation that may result in hyperpigmentation and black spots on a dog’s skin. As hyperpigmentation results from chronic irritation, these spots will lie flat as part of the skin and will not have a mass-like appearance.

Bacterial skin infections (usually Staphylococcus sp.) cause black spots on the skin in the same manner as injuries, as the infection damages the skin’s barrier. This damage is a result of the inflammation present secondary to the infection.

When the infection clears in response to treatment, the spots should fade as well. It is normal to see black spots remain much longer after the infection is resolved. The circular sores associated with bacterial infections are referred to as epidermal collarettes. As these sores resolve, the skin becomes hyperpigmented.

Some of these signs are shared by other diseases, like certain immune disorders and neoplasias. Your veterinarian will be able to determine the true cause of the symptoms using their experience and diagnostic tools.

Four Common causes of bacterial skin infections in dogs

Any illness that weakens your dog’s immune system increases the chance of a bacterial skin infection.  The following interfere with the skin’s health in a more direct way:

1. Cushing’s Disease

Cushing’s Disease decreases the amount of normal collagen found in the skin, causing the skin to become weak and thin with extra folds. The skin may develop dark lesions as well as small raised bumps. Unfortunately, this makes the dog a prime candidate for a secondary bacterial infection. View pictures of dogs with Cushing’s disease. 

2. Hypothyroidism

Hypothyroidism decreases the activity of certain enzymes resulting in changes to the natural skin barriers. The skin develops a darker pigment, there are areas of hair loss and the skin becomes more susceptible to bacterial infection.

3. Flea bite dermatitis

Flea bite dermatitis is an allergic reaction to flea saliva. Your dog will develop itchy skin with hair loss starting on the back and extending to the base of the tail.  If left untreated it can progress forward up to the neck and head. Your dog’s licking and chewing the itchy skin causes scabs and red bumps, leaving the skin vulnerable to secondary bacterial infection.

4. Sarcoptic scabies and demodex

Sarcoptic scabies and demodex are two parasitic mites that can infect a dog’s skin. Demodex is a natural inhabitant of dog skin and only becomes an issue when a dog’s immune system is compromised. On the other hand, scabies is spread from dog to dog. 

Both of these infections cause great damage to the skin and increase the chance of a bacterial infection setting in. An infection of scabies or demodex is commonly called “mange”.  You will see hair loss and red, scaly skin. 

Note: Sarcoptic mange or “scabies” is contagious to people.

More types and causes of bacterial skin infections

Pyodermas can be classified by the depth of tissue affected. Allergies, immune disorders, and some cancers often underly a bacterial infection.

Surface pyoderma

Only the outermost layer of skin, the epidermis is affected. “Hot spots” or acute moist dermatitis and skin fold pyoderma are examples of a surface pyoderma.

Hot spots

Canine “hot spots” are self-induced. When a dog scratches and chews at an itch they may cause small breaks in the skin. As they continue to chew the nerves become inflamed and cause more itching which leads to more chewing.  

A hot spot can start as a tiny red spot and very quickly become a large red lesion infected with bacteria.  Often they ooze blood-tinged fluid.    

The initial itch can be due to fleas, insect bites, allergies, anal sac impaction, or matted fur that pulls at the skin and causes an itch. Additionally, boredom or anxiety can make a dog chew or lick incessantly causing a hot spot.

Skin fold pyoderma (intertrigo)

The friction caused by skin rubbing against skin causes inflammation. The area becomes moist and therefore an ideal place for bacteria to grow. Yeast also likes this environment and is often an additional pathogen (disease-causing organism).  

Skin fold pyoderma appears as reddened skin with discharge. There may be a foul odor. The skin folds may need to be spread open to see the inflammation.

Superficial pyoderma

The outer layer of the skin, the epidermis is affected along with the hair follicles. Hair loss, redness, crusty lesions and bumps may be seen. Puppy pyoderma and folliculitis are examples of superficial pyodermas.

Puppy pyoderma

This is one bacterial skin infection that doesn’t typically have an underlying disease involved. Puppies’ skin is sensitive and when it becomes irritated from things in the environment the bacteria that normally live on the surface of a dog’s skin cause an infection.

It usually occurs on sparsely haired areas such as the belly, armpits and groin. Puppy pyoderma appears as red bumps or lesions that are sometimes scaly and itchy.  

Folliculitis

A common ailment of dogs, folliculitis causes a moth eaten appearance to the hair coat along with redness and itching. Raised red bumps or pustules and flaking, crusty skin may be seen. Sometimes a foul odor may be noticed. Folliculitis is often seen secondary to allergies. View more pictures of folliculitis in dogs.

Deep pyoderma

In deep pyoderma, the deeper levels of the skin, the dermis and the subcutis are affected. This may start as superficial pyoderma and progress to a deep infection. In some cases, a deep pyoderma may arise on its own. It’s often secondary to a demodex infection.  

Redness, swelling, nodules, or fistulous tracts draining bloody fluid or pus may seen. There may be a foul odor. This is a painful condition, so prompt veterinarian care is necessary. 

There are different types of deep pyodermas, including furunculosis and lick granulomas. Furunculosis is when the deep layers of the skin closest to the hair follicles become infected or red and painful nodules are seen. These usually occur in between the toes, around the anus, and on the face.

Also known as acral lick dermatitis, lick granulomas cause a localized lesion that is red, bumpy, and raised. It starts with excessive licking of the same spot. The licking may come from an allergic itch or it could be behavioral. These granulomas usually occur on the wrist, ankles, hocks, or feet. They can become fairly large and unsightly, looking like a tumor.  

Diagnosing bacterial skin infections in dogs

Like any disease, obtaining a diagnosis starts with the clinical signs or symptoms. Your veterinarian is familiar with the different types of lesions affecting various areas of the body and this information aids in diagnoses. 

But because most skin infections have similar clinical signs, tissue sampling is important. Tissue samples can be obtained via impression smear, skin scraping, or fine needle aspirates.

The samples are examined microscopically and may be submitted for culture and sensitivity testing. Any bacteria cultured is then tested for its sensitivity to various antibiotics. This lets the doctors know which antibiotic will be the most effective for your dog.

Red, itchy skin! Do I need to take my dog to the vet?

Besides the most minor cases, it’s a good idea to have skin irritations checked by a vet. Skin disease can progress quickly, so it’s smart to check for any serious diseases that may be the underlying cause.

Here are some reasons your dog needs to be seen by a veterinarian immediately:

1. The skin disease is extensive, covering a large portion of your dog’s body
2. Your dog is showing other signs of illness such as trembling, vomiting, or not eating
3. If your dog’s skin is bleeding or oozing

Let your vet know the severity of the symptoms so that they will get you in to have your dog seen right away. Untreated skin infections can lead to systemic disease causing serious illness. Moreover, if your dog seems uncomfortable or in pain from constant itching and scratching, you may want to see a vet on an emergency basis to relieve the discomfort. 

If the affected area is small and the symptoms are mild, you can try treating your dog on your own with commercial products. There are many shampoos, ointments and all natural remedies for your dog’s itchy, inflamed skin. However, it’s a good idea to consult your veterinarian before using any “at home” treatment options so that they can recommend ones that are safe and effective. 

When attempting a home remedy monitor your dog closely. If the symptoms worsen or there is no improvement after a few days, you need to see a veterinarian. It’s imperative to get your dog on the right course of medications quickly to ensure a good outcome.

Treatment options

Surface pyodermas and some superficial pyodermas may resolve with daily bathing using a medicated shampoo prescribed by your veterinarian.  

Oral antibiotics are often necessary to cure bacterial skin infections. In addition, medicated shampoos, sprays, or ointments are normally prescribed. It may take three to four weeks to be rid of the infection.  Resistant cases may take eight to twelve weeks to cure. As the dog parent you must be diligent, bathing your dog as often as the vet prescribes.

It’s necessary for your vet to treat the underlying disease to fully rid your dog of the infection. The cost to treat your dog’s pyoderma varies depending on the severity of the infection and how quickly your dog responds to treatment. A mild infection may cost from $200 to $400 to treat. A serious infection could go much higher, costing from $500 to $1000.

These estimates include the exam fee, bloodwork, tissue sampling, cytology (microscopic evaluation of cells), culture and sensitivity, antibiotics, medicated shampoos and sprays. The underlying disease will also need to be addressed and that will involve further diagnostics and medications.

Zoonosis: can I catch my dog’s nasty skin infection?

The majority of canine bacterial skin infections are caused by Staphylococcus species, some of which are contagious to people. People with compromised immune systems should use care to not come into contact with the infected dog and the dog’s bedding. Healthy individuals should wash hands after handling the dog and perhaps temporarily forgo sharing the bed.

What can I do to prevent a bacterial skin infection in my dog?

Prevention of any disease starts with good nutrition and good hygiene. Regular bathing, keeping their ears clean and wiping skin folds daily goes a long way for skin health. Good grooming, trimming excess hairs of the feet and regular brushing to avoid mats is also important. Keeping up with flea and tick preventative is helpful as well.  

Regular exercise helps keep your dog mentally healthy and may keep them from the excessive licking and self mutilation that bored, anxious dogs engage in.