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Demodicosis is the overgrowth of a mite (Demodex canis) found within the hair follicles. Mites are passed from the mother to the puppy within the first few days of birth and the presence of very low numbers  on dogs is normal.

Clinical disease (demodicosis) occurs when the number of mites increases to excessive and harmful levels, due to the dog’s immune system being unable to control the mites  allowing overgrowth.

There are two forms of demodicosis:

-       Juvenile-onset demodicosis, where the immune system of growing or young adult dogs seems to be unable to identify the mites as foreign, with a genetic predisposition present.

-       Adult-onset demodicosis, where the overgrowth is frequently associated with a poor or compromised immune system. This can result from underlying conditions such as Cushing’s disease, hypothyroidism, immunosuppressive drugs, or cancer.

Clinical Signs

Mite overgrowth destroys the hair follicles leading to hair loss. Bacteria and yeasts can invade the skin via the holes produced by this hair loss (folliculitis) leading to secondary infections with scabs and spots.

 The disease is termed localized when hair loss occurs only in isolated, patchy areas. Localised demodicosis is rarely itchy.

With generalized demodicosis, hair loss and lesions may occur all over the body and be extensive.  Blackheads, pimples, red bumps, and bleeding areas may be present.  Scabs often indicate secondary infection, which can cause itchiness.


Diagnosis is based on finding Demodex canis mites in samples taken from the skin.  Samples are taken by scraping the skin or plucking hairs and examined under the microscope.  Other laboratory tests may be indicated in dogs with adult-onset demodicosis in case of underlying disease.


Many cases of localized demodicosis will resolve on their own, once the dog’s immune system becomes competent and require only monitoring.  However it is important to watch for new areas of hair loss as it may progress to a generalized form and require treatment.

For dogs with generalized demodicosis of juvenile onset, all secondary bacterial infections are treated, and efforts are made to improve the overall health of the animal.   Measures include deworming, vaccinations, nutrition, and desexing.

In cases of adult-onset generalized demodicosis, all secondary bacterial infections are treated.  Sometimes infections are so severe that they must be treated first.  An underlying cause must also be addressed. 

There are medications used in canine demodecosis that are not licensed for use but are well-documented and can be very effective. In more serious cases they may be required for effective resolution and cure. Careful discussion with your vet is required to decide if these may be needed.

Successful management of demodicosis can be difficult.  Localised cases are rechecked every few weeks until the dog outgrows the disease.  Dogs with juvenile-onset generalized disease are usually rechecked monthly until secondary infections are resolved, then every 4-8 weeks throughout the course of therapy which may last for up to 4 months.

Some animals with generalized disease are not cured and must be treated periodically for life to control the lesions.

Prognosis is very good for puppies with localized demodicosis and 85% of dogs with juvenile-onset generalized demodicosis can be cured. 

Resolution of adult-onset cases varies based on the overall health of the animal and the presence of any underlying diseases.