Fungal Infections in Dogs (Dermatomycosis): Symptoms, Diagnosis and Treatment

Fungal infections in dogs, known in veterinary terms as dermatomycosis, are infections of the skin, the coat and, less often, the claws by fungi. In everyday speech they are all simply called “fungus”, but two separate conditions stand out in dogs: dermatophytosis (ringworm), which is contagious, and Malassezia infection, which develops when a yeast that already lives on the dog’s skin overgrows. The two differ in cause, contagiousness and treatment.

This distinction matters especially for owners of the English Staffordshire Bull Terrier (Staffordshire Bull Terrier), known in Turkey as the English Staff. The breed has sensitive skin, and allergies, demodicosis and the colour dilution alopecia seen in blue dogs can easily be mistaken for a fungal infection. We summarise the breed’s overall health profile in our English Staffy guide. In this article we explain how fungal infections are recognised, which tests your vet relies on and what you need to do at home. Diagnosis and treatment are always decided by your vet.

What Is Dermatomycosis? The Two Main Types of Fungal Infection in Dogs

Dermatomycosis is a general term for fungal infections of the skin. In Turkish sources it is often used as a synonym for dermatophytosis, but in practice the skin fungi seen in dogs fall into two groups:

	Dermatophytosis (ringworm)	Malassezia (yeast)
Cause	Microsporum canis, Trichophyton species, the soil-dwelling Nannizzia gypsea	Malassezia pachydermatis, which is also found on normal skin
How does it start?	Contact with an infected animal, person or object	Overgrowth on a background such as allergy, hormonal disease or skin folds
Typical appearance	Hairless patches, broken hairs, scaling, crusts	Greasy, smelly, red skin; the ears and the skin between the toes are involved
Itching	Usually mild, but variable	Usually marked
Contagiousness	Spreads to other animals and to people	Not considered contagious in practice
Treatment focus	The dog and the home together	The yeast and the underlying cause together

Dermatophytosis (Ringworm): The Contagious Fungus

Dermatophytes are fungi that feed on the keratin in hair and in the outer layer of the skin. The main culprits in dogs are Microsporum canis, Trichophyton mentagrophytes and Nannizzia gypsea, a soil fungus formerly called Microsporum gypseum. Infection usually spreads through direct contact with an infected animal; objects such as combs, bedding and collars can also carry the spores. Spores can survive on objects and carpets for up to 18 months.

Not every contact leads to infection. The risk rises in puppies, in dogs under stress or kept in crowded conditions, in dogs that dig in soil and in animals with weakened immunity. According to the Merck Veterinary Manual, the infection can clear on its own within 6-12 weeks in a healthy animal; it is still treated because it can spread to the environment and to people during that time.

Malassezia (Yeast): A Sign of an Underlying Problem

Malassezia pachydermatis is a yeast normally found on the skin of healthy dogs, especially around the mouth and between the toes. The trouble starts when the skin barrier breaks down and the yeast overgrows. The most common backgrounds are allergic skin disease (especially atopic dermatitis), hormonal diseases such as hypothyroidism, skin folds and warm, humid weather.

That is why Malassezia is usually not a disease on its own but a sign of another problem. If the underlying cause is not controlled, it comes back soon after treatment ends. It rarely spreads to healthy people; however, rare infections have been reported in people with severely weakened immunity, so hand hygiene still matters.

Deep (Systemic) Fungal Infections

Much less often, some fungi can settle in the nasal cavity, the lungs or other organs through spores inhaled from soil. These conditions are different from skin fungus and may show general signs such as coughing, fever, loss of appetite, weight loss, eye problems or lameness. Nasal aspergillosis, for example, can cause bloody nasal discharge, sneezing and nosebleeds; we cover it alongside other causes in our article on nosebleeds in dogs. If you see these signs, contact your vet without delay.

Symptoms of Fungal Infections in Dogs

Signs of Dermatophytosis

• One or more hairless patches, round or irregular in outline. The centre of a patch may heal and start to regrow hair.
• Fragile, broken hairs that come out easily.
• Scaling, dandruff, crusting and redness.
• Itching is usually mild, but it can be marked in some dogs.
• Less often, roughened and breaking claws; in dogs that dig, a swollen lesion on the nose (kerion).

The “ring” appearance is not a must. Dermatophytosis can mimic allergy, bacterial skin infection or demodicosis; it cannot be diagnosed just by looking at it.

Signs of Malassezia

• Greasy, sticky skin and a brown or blackish discharge that mats the hair.
• A sour or musty smell.
• Marked itching and redness; hair loss from constant licking and scratching.
• Darkened, thickened skin in long-standing cases.
• Brown, waxy debris in the ears and inflammation of the outer ear.
• Redness between the toes, brown debris at the base of the claws and reddish-brown discolouration of the claws.

The armpits, groin, underside of the neck and skin folds are also commonly affected.

Fungus, Allergy or Something Else in an English Staffy?

Skin problems are the most common issue English Staffy owners face. When itching, redness and hair loss appear, “fungus” is the first thing that comes to mind, but other conditions that look the same are also common in this breed. Applying antifungal cream for months on a wrong guess wastes time and lets the real problem grow.

Condition	Clues that set it apart from a fungal infection	What the vet will check
Allergy (atopic dermatitis, food allergy)	Itching dominates; paw licking, ears, armpits and belly involved	Ruling out other causes, elimination diet
Demodicosis	Hairless patches in young dogs, especially on the face and front legs	Deep skin scraping, trichogram
Colour dilution alopecia (CDA)	Permanent thinning only in blue (dilute) areas, starting along the back	Trichogram, skin biopsy
Hypothyroidism	Symmetrical hair loss, lethargy, unexplained weight gain	Blood tests
Bacterial skin infection (pyoderma)	Pimple-like bumps, ring-shaped crusting	Cytology, bacterial culture if needed

These conditions can also occur together. Yeast and bacterial infections often accompany allergies; treating the yeast works, but the problem returns unless the allergy is brought under control. We explain allergy signs and management in our article on English Staffies and allergies. For hair loss in blue dogs, see our article on colour dilution alopecia (CDA), and for thyroid signs, see hypothyroidism in dogs.

How Does a Vet Diagnose a Fungal Infection?

No single test catches every case; vets usually combine several methods. During the examination your vet will also ask whether anyone at home has an itchy skin lesion and whether your dog has recently been in a shelter or a boarding facility, or in contact with a new animal.

• Wood’s lamp: A special ultraviolet lamp. Hairs infected with Microsporum canis glow apple green; other dermatophytes do not glow, so a negative result does not rule out a fungal infection.
• Trichogram (hair microscopy): Hairs taken from the lesion are examined under a microscope; fungal spores may be visible on infected hairs.
• Fungal culture: Hair and scale samples are placed on a special culture medium. Results take from a few days to three weeks; culture identifies the fungal species and is also used to monitor treatment.
• PCR: Detects fungal DNA quickly but cannot tell live spores from dead ones, so it can still be positive after treatment.
• Cytology: A sample taken from the skin with tape or a glass slide is checked for the number of Malassezia. It is the most practical way to diagnose yeast.
• Skin scrapings, biopsy and blood tests: These may be requested to rule out demodicosis, investigate unusual lesions or look for underlying causes such as allergy or hormonal disease.

Applying cream, using a medicated shampoo or giving leftover medication at home before the appointment can distort test results. Instead, take dated photos of the lesions; this helps your vet assess how things are progressing.

How Are Fungal Infections in Dogs Treated?

The treatment plan, medication and duration are decided by your vet, so we do not give drug names or doses here. Understanding the general approach helps you see why treatment should not be stopped halfway.

Treating Dermatophytosis

A two-pronged approach is usually used. An antifungal shampoo or rinse applied to the whole body clears spores from the coat and reduces spread, while an oral antifungal medication treats the infection in the hair follicles. Applying cream only to the lesion is usually not enough and makes relapse more likely.

Treatment usually lasts at least 4-6 weeks, sometimes longer. Lesions disappearing does not mean treatment is over; your vet ends treatment when a follow-up culture or PCR test comes back negative. Some oral antifungal medications can have side effects, so interim check-ups may be requested. Clipping the coat is not needed in every case; if it is, it should be done on your vet’s advice and without irritating the skin.

Treating Malassezia

In mild cases, antiseptic and antifungal shampoos that work against yeast, together with suitable ear products, are often enough. In widespread cases, or those that do not respond to topical treatment, oral medication may be added. The deciding factor is finding the underlying cause: any treatment given without managing the allergy, hormonal disease or skin folds will only be temporary.

Creams sold for people, or the vinegar and oil remedies suggested online, are no substitute for the treatment your vet recommends; they can irritate the skin and delay a correct diagnosis.

Can Dogs Pass Fungal Infections to People? Hygiene and Cleaning at Home

Dermatophytosis is a zoonotic disease, meaning it can pass from dogs to people. Young children and people with weakened immunity are at greater risk. In people it usually appears as itchy, red, scaly ring-shaped lesions with raised edges, and it is easily treated. If such a lesion appears on someone at home, that person should see a doctor and the dog should be taken to the vet.

Malassezia poses practically no risk to healthy people. Even so, washing your hands after touching your dog is a good habit, especially if there is a baby or someone with weakened immunity at home. While your dog is being treated for dermatophytosis, pay attention to the following at home:

1. Keep your dog in one or two easy-to-clean rooms during treatment. But do not leave them completely alone for long periods; especially in puppies, this can lead to behaviour problems.
2. Wear gloves when caring for your dog, then wash your hands thoroughly.
3. Clean mechanically first: pick up hair and scales with a vacuum cleaner and a damp cloth, and wash surfaces with detergent. Then use a disinfectant whose label states that it is effective against fungi.
4. Wash beds, blankets and towels in the washing machine; shampoo or steam clean carpets.
5. Clean or replace combs, brushes, collars and food bowls.
6. Have the other cats and dogs in your household checked by a vet as well. Some animals can carry the fungus without showing any signs.
7. Keep cleaning regularly until your vet says treatment is complete.

When Should You See a Vet?

When you notice a change in the skin, an early examination always makes treatment easier than waiting. Do not put off an appointment if:

• You notice hairless patches, broken hairs or crusting.
• A ring-shaped lesion has appeared on a person or another animal at home.
• The skin is greasy and smells bad, or brown debris is building up in the ears.
• The itching is severe enough to disturb your dog’s sleep, or your dog licks their paws constantly.
• The same problem returns soon after treatment ends.
• A skin problem started shortly after you brought home a new puppy. In that case, also read the steps to take if you bought a sick puppy.
• Skin signs are accompanied by lethargy, loss of appetite, coughing or nasal discharge. In this case, go without waiting.

Frequently Asked Questions

Do Fungal Infections in Dogs Go Away on Their Own?

In a healthy dog, dermatophytosis can clear on its own within 6-12 weeks. However, it is treated because it can spread to the home, to other animals and to people during that time. Malassezia, on the other hand, does not clear on its own as long as the underlying cause persists.

Can I Catch a Fungal Infection from My Dog?

Dermatophytosis (ringworm) can spread to people; children and people with weakened immunity are particularly at risk. Malassezia practically does not spread to healthy people. In either case, wash your hands after touching your dog.

How Long Does Treatment Take?

For dermatophytosis it usually takes at least 4-6 weeks, sometimes several months, and the decision to stop is based on follow-up tests rather than appearance. For Malassezia the first course may be shorter, but the problem returns if the underlying cause is not managed.

When Can a Dog with a Fungal Infection Meet Other Dogs Again?

With intensive treatment, a dog with dermatophytosis stays contagious for about three weeks, and for longer with fewer precautions. Ask your vet before taking your dog to the park, a boarding facility or a groomer. Malassezia usually does not require such restrictions.

Are English Staffies Prone to Fungal Infections?

With dermatophytosis, the risk depends more on age, environment and contact than on breed. What stands out in the English Staff is a skin barrier weakened by the breed’s tendency to allergies, and the recurring yeast and bacterial infections that follow. We list the breed’s other predispositions in our article on Staffordshire Bull Terrier health issues.

A fungal infection in dogs is not a single disease: contagious dermatophytosis and Malassezia, which keeps returning in the shadow of allergy, call for different approaches. In a breed with skin as sensitive as the English Staffy’s, the right step is to let your vet reach a diagnosis with tests rather than guessing from the skin, to complete the treatment and to include your home in it as well.