If Your Dog Keeps Scratching — A Guide to Demodicosis Symptoms, Transmission, and Treatment

Infection/ParasitesDiseasesMeongsiljang Veterinary Advisory Board

Canine demodicosis is a parasitic skin disease caused by an overgrowth of Demodex mites. While the localized form may resolve on its own, the generalized form requires consistent treatment, and early detection is key to a full recovery.

What Is Canine Demodicosis?

Checking for hair loss in areas affected by canine demodicosis

Canine demodicosis is a parasitic skin disease caused by the overgrowth of Demodex canis mites in hair follicles, leading to hair loss and skin inflammation. Demodex mites are normally present in a dog's hair follicles and sebaceous glands, typically transmitted from mother to puppy through direct contact at birth, where they quietly reside in the follicles. However, if the dog's immune system weakens or if there is a genetic predisposition, the mites can multiply excessively, causing symptoms such as hair loss and skin inflammation. Localized demodicosis, where lesions are confined to a few areas, often resolves on its own without treatment. But if the lesions spread, it can progress to generalized demodicosis, which requires much longer treatment, making early diagnosis crucial.

Transmission Routes and Causes

Demodex mites are primarily transmitted to newborn puppies through direct contact with their mother, including nursing, during the early weeks of life. Once transferred, these mites remain dormant within the hair follicles until the puppy’s immune system weakens, at which point they begin to overpopulate.

Genetic predisposition: Genetic immune deficiencies related to demodicosis have been reported, making certain breeds such as Bulldogs and Shar-Peis more susceptible to developing the condition.

Young age: The localized form typically occurs in young puppies, with onset usually occurring between 3 and 8 months of age.

Immunosuppressed state: In adult dogs, the generalized form may develop secondarily if they have concurrent illnesses or are undergoing immunosuppressive treatments, such as allergy or cancer therapy. In these cases, it is crucial to identify any underlying conditions.

Symptom Checklist: Localized vs. Generalized Forms

Localized Symptoms

Hair Loss: Several circular or patchy areas of hair loss may appear on the face, front legs, paws, and other regions.

Scaling and Flaking: The skin in hairless areas becomes dry and develops scales (dandruff).

Mild Erythema: The skin may appear slightly red, but itching is absent or mild.

Systemic Symptoms

Generalized Hair Loss: Hair loss spreads widely across multiple areas, including the face, trunk, and legs.

Skin Changes: The skin thickens and develops hyperpigmentation; in chronic cases, it may take on a slate-gray hue.

Purulent Lesions: Secondary bacterial infections can cause deep folliculitis, pus, crusting, and a strong odor.

Comparison of Symptoms Between Localized and Generalized Demodicosis

Signs That Require Immediate Veterinary Attention

If hair loss suddenly spreads rapidly to multiple areas, or if pus or discharge appears on the skin, or if there is a strong foul odor, you should visit a veterinary clinic immediately. When severe generalized demodicosis is accompanied by secondary bacterial infections (such as pyoderma or deep folliculitis), the overall condition can deteriorate significantly, with symptoms including hemorrhagic discharge, thick crusts, and enlarged lymph nodes. In the past, such severe generalized cases could progress to the point where euthanasia was considered, making prompt treatment essential.

Diagnosis — Skin Scraping Test

Demodicosis is confirmed through a skin scraping test. A veterinarian uses medical instruments to deeply scrape the skin and examines the Demodex mites under a microscope to assess their number and developmental stage. If a large number of immature stages, such as larvae and eggs, are found in addition to adults, it is considered an active infection. If mites from deep hair follicles are difficult to extract, the skin may be manually squeezed to push them out, or additional tests such as adhesive tape testing or a skin biopsy may be performed. In breeds like the Shar-Pei, where extracting mites is particularly challenging, a biopsy may be necessary. Treatment progress is monitored through follow-up tests, typically continuing until two consecutive negative results are obtained at two- to three-month intervals.

Treatment — Localized vs. Generalized Forms

Localized Form Treatment: The localized form often improves on its own without specific treatment, so we typically monitor the condition and schedule regular follow-up exams. However, if the lesions begin to spread systemically, more aggressive treatment becomes necessary.

Systemic Form Treatment: Isoxazoline-class medications (afoxolaner, fluralaner, sarolaner, and lotilaner) are currently recognized as the most effective treatments. They have replaced older drugs like ivermectin and amitraz (amitraz is rarely used today). If a secondary bacterial infection is present, antibiotics may be prescribed alongside the primary treatment.

Treatment Duration: Treatment should not be stopped until two consecutive skin scraping tests come back negative. This process usually takes 3 to 6 months.

Isoxazoline medication treatment for canine demodicosis

Home Care Tips

Alongside medical treatment, there are several care steps you can consistently follow at home.

Nutritional Support: Feeding a diet or supplement rich in omega-3 fatty acids can help restore the skin barrier.

Stress Reduction: Stress weakens the immune system and can worsen symptoms, so maintaining a consistent daily routine and providing appropriate exercise is essential.

Medicated Shampoo Care: Use veterinarian-prescribed shampoos regularly as directed, and ensure your pet is thoroughly dried after bathing.

Limit Contact with Other Pets: For safety, minimize direct contact with other animals during treatment, especially with puppies or senior dogs who may have weaker immune systems.

Medicated shampoo for home management of canine demodicosis

High-Risk Breeds and Prevention of Recurrence

Breeds such as Bulldogs, Shar-Peis, Dachshunds, and Dobermans have been reported to have a genetic susceptibility to demodicosis, so it is important to closely monitor their skin condition from a young age and schedule regular veterinary check-ups. Treatment options must always be selected in consultation with a veterinarian; particular caution is needed with ivermectin and similar medications previously used, as they carry risks of neurotoxicity and retinal damage in Collie-type breeds. Additionally, if a full-body form of the condition develops in an adult dog, it may indicate an underlying condition such as Cushing’s disease. Therefore, the key to management is identifying the root cause through blood, biochemical, and hormonal tests, and addressing it accordingly.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can demodicosis be transmitted to humans?

Demodex mites in dogs are not transmitted to humans. The species of Demodex that infest dogs and those that infest humans are different, so cross-infection is extremely rare. You can care for your child with peace of mind.

Should I take my pet to the vet for localized demodicosis?

It’s important to first get a veterinary diagnosis to confirm that the condition is localized. If there’s no improvement within 2–3 months, or if the lesions increase in number, a follow-up visit is essential. Left untreated, the condition can progress to a systemic form.

Is it okay for my dog to play with other dogs during treatment?

Although the risk of liver disease transmission to adult dogs is low, it’s safest to limit direct contact with puppies or senior dogs with weakened immune systems until treatment is complete.

Can generalized demodicosis be cured?

With consistent treatment, a full cure is possible. However, since the condition can recur when the immune system is compromised, it’s important to manage any underlying health issues as well. Stopping treatment prematurely significantly increases the risk of relapse.

Are isoxazoline-class medications the same as heartworm preventatives?

They’re different. Isoxazolines are a separate class of medications used to treat ticks and fleas. Since their active ingredients differ from those in heartworm preventatives, your veterinarian will prescribe them separately for demodicosis treatment.

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References

[1] Mueller RS, Treatment protocols for demodicosis: an evidence-based review, Veterinary Dermatology, 2004

[2] Scott DW, Miller WH, Griffin CE, Small Animal Dermatology, 6th Ed, W.B. Saunders, 2001

[3] Mecklenburg L et al, Hair Loss Disorders in Domestic Animals, Blackwell Publishing, 2009

[4] Beale K, Canine demodicosis, Clinical Techniques in Small Animal Practice, 2006