Cat scratching it's head.


Pyoderma literally means skin infection with the formation of pus. This can occur in all pets and is uncomfortable and irritating. The cause can be simple, for example a bite or scratch or more complicated and signify hidden disease.

What causes pyoderma?

All skin is covered in a layer of bacteria. Healthy skin acts as a physical barrier to stop these bacteria entering the skin. Skin also has an effective immune system to manage any bacteria that enter the skin layers. Pyoderma occurs when the bacteria enter the skin and overwhelm the protective measures and cause infection.

There are many possible causes of pyoderma ranging from the very simple to more complex:


A sharp object, splinter, bite wound or scratch can penetrate the skin allowing entry of bacteria. Burns strip away protective upper layers of skin, in older or poorly mobile animals skin can be burnt by urine scalding. Pressure sores can also become infected in immobile animals. Dirty, matted coats can create areas of skin trauma and overgrowth of bacteria. Skin folds and other areas where haired skin chafes, such as the between the toes, can cause microtrauma to the skin.


Any animal with a condition that causes itching is likely to cause wounds by scratching, biting or rubbing against objects. Many conditions cause itching.

  • Parasites – most commonly, flea or mite infestations.
  • Fungi – ‘ringworm’ is the most common fungal infection in pets.
  • Allergies – usually fleas, food or allergens in the air such as pollens, house dust mites.
  • Anal gland impaction
  • Ear disease


Malnutrition affects the ability of the skin to form a protective barrier. A balanced diet with adequate calories is important for skin health. Low levels of specific nutrients, for example, Zinc deficiency can also cause skin ulceration.

Diseases affecting hormonal balance such as an underactive thyroid and Cushings disease also result in skin disease

Autoimmune disease occurs when the animal’s own immune system damages an organ. The skin can be a target for autoimmune disease often resulting in pyoderma.

Suppression of the immune system with drugs such as chemotherapy drugs or steroids can affect the immune function of the skin. Long term illness such as cancer, liver disease, kidney disease, chronic viral infections can also compromise skin health.

Young animals

The immune system of young animals is not as well developed as in the adult. Their skin is also thinner. For example in puppies pyoderma (sometimes called impetigo) can spread more quickly and cause more severe disease than in the adult dog.

What does pyoderma look like?

There is a vast spectrum of signs of pyoderma, from a ‘hot spot’ to generalised hair loss and scaling. A hot spot is a small area of inflammation, it may look like ulcer which appears almost overnight. Animals do this when a condition is extremely itchy. It is an area of self-trauma. This is often seen with anal gland disease, fleas or ear disease.

In other cases, the skin appears red and inflamed. This is often seen most clearly where skin is poorly haired and thin, so on the belly, groin or in the ‘armpits’. A rash or pustules (pimples) may be seen. There is often hair loss or the hair is sticky as the skin crusts at the base of the hairs. There may be skin ulcers, craters of skin loss, varying in depth and a foul smell on the skin.

What can you do if your pet has pyoderma?

If a small area of skin is broken by a simple injury then clipping the hair away and cleaning twice daily with a weak salt solution will be sufficient. However, if your dog is scratching and uncomfortable or a large area is affected or you see pustules or smell pus, then visit your vet.

Superficial pyoderma

As we have seen pyoderma can occur for simple reasons. In these cases after your vet examines your dog they may choose to use a topical antibacterial gel, cream or shampoo. These cases are usually called superficial pyoderma as they affect only the top layers of skin. Sometimes other treatments are required, parasite treatments, medications to stop the itch-scratch cycle (anti-itch drugs) or antibiotic tablets. Superficial pyoderma should resolve in 2-3 weeks.

Deep pyoderma

If your pet has a deep pyoderma or your vet suspects an underlying condition causing the pyoderma then investigations may be required. Usually a bacteria called Staphylococcus causes pyoderma but sometimes other bacteria are involved. A tape strip test can be used to initially identify the presence and type of bacteria. Your vet may also send samples for culture to the laboratory. This means that the correct antibiotic can be used. Yeast infection is often identified at this time and may require treatment. A skin scrape can be used to identify parasites. Samples of hair and skin can be sent to the laboratory to check for fungal infection.

Complicated deep pyoderma

If no obvious cause is found then a skin biopsy and blood tests may be needed to rule out underlying disease or allergy.

Deep pyoderma will need a long course of antibiotics, these can be oral medication and shampoos or gels as well. Your vet may suggest a dermatology diet or a diet designed to remove foods your pet may be allergic to. Dietary supplements, such as omega 3/6 fatty acids may be recommended. Just as in superficial pyoderma, parasite control, anti-itch medication and other medications for underlying conditions may be required.

Pyoderma can be a frustrating condition for you and your pet but with perseverance and the correct care most cases will resolve completely.