What causes mange in dogs?

Mange matters because it’s one of those problems that looks small at first—an itchy patch, a thinning coat—but can quickly affect an entire household, derail a new adoption, or lead to costly veterinary care if ignored. Recognizing the causes and early signs helps you protect your dog, other pets, and people in the home.

Mange and your dog — what’s at stake

New puppies, rescue dogs, and animals from high-density settings like shelters or kennels are common situations where mange becomes a concern. I typically see cases where an excited adopter brings home what looks like a minor skin issue and then faces repeated vet visits, treatment costs, and emotional stress as the problem spreads or fails to resolve.

Beyond the emotional strain, untreated mange may lead to secondary bacterial or yeast infections that require antibiotics, pain control, and longer recovery—raising the financial stakes. For households with children, seniors, or immunocompromised people, there is also a zoonotic risk: some types of mites can temporarily irritate human skin, which adds a public-health dimension to what began as a pet problem.

What causes mange in dogs — the short version

Mange in dogs is caused by microscopic mites that live on or in the skin; the main culprits are Sarcoptes (sarcoptic mange), Demodex (demodectic mange), and less commonly Cheyletiella, and each behaves differently in how it spreads and how the body reacts.

Sarcoptes mites are highly contagious from dog to dog and may cause intense itching and visible lesions within weeks, while Demodex mites normally live on most dogs in small numbers and may cause problems when they overgrow—often linked to immature or suppressed immune systems. Typical clinical outcomes include strong itching, hair loss in patches or generalized thinning, and vulnerability to bacterial or yeast overgrowth when the skin barrier is compromised.

How microscopic mites damage a dog’s skin

Mites interact with the skin in ways that provoke both direct damage and an immune reaction. Sarcoptes mites tend to burrow into the outer layers of the skin to lay eggs and feed, which directly irritates nerve endings and disrupts the skin’s surface. Demodex mites live deeper in hair follicles and sebaceous glands; in low numbers they may be harmless, but if they multiply they can clog follicles and disrupt normal hair and oil production.

The immune system’s response to mite proteins and secretions is a large part of the clinical picture. In some dogs, the response is disproportionately intense, producing inflammation, redness, and extreme itch. Repeated scratching and rubbing further damage the skin barrier, creating openings where bacteria and yeast can invade—this is why many dogs with mange have secondary pustules, crusting, and a strong odor.

Lifecycle differences matter for control: Sarcoptes has a short life cycle with eggs, larvae, and adults on the host surface, which helps explain rapid spread and dramatic itching; Demodex spends most of its life in follicles and is less contagious, so treatment strategies and expectations can differ.

Who’s most at risk: situations and factors that increase mange

Puppies and young dogs are often at higher risk of demodectic mange because their immune systems are still maturing; I also see demodex flare when an adult dog’s immunity is suppressed by illness, steroids, or other stressors. In contrast, sarcoptic mange can affect dogs of any age because of its ease of transmission.

High-density environments—shelters, boarding facilities, dog parks after close contact—are settings where sarcoptic mites are more likely to pass from animal to animal. A single undiagnosed, itchy dog in a kennel can seed multiple cases quickly if isolation and sanitation aren’t in place.

Additional triggers that may increase the chance of mange becoming a problem include chronic stress, poor nutrition, concurrent illnesses (like hormonal or metabolic disease), and heavy parasite burdens that tax the immune system. Those factors may not cause mites to appear, but they can contribute to overgrowth or more severe disease once mites are present.

Red flags: symptoms that warrant immediate vet attention

Persistent, intense itching that does not respond to basic flea control is a classic red flag for sarcoptic mange; hair loss that begins around the ears, elbows, and face and spreads rapidly should prompt a prompt veterinary evaluation. Demodectic mange often shows as localized patches of hair loss, but generalized forms can be severe and painful.

Look for crusting, scabbing, pustules, and a foul or yeasty smell—these suggest secondary infection that often requires antibiotics in addition to mite-directed therapy. Systemic signs such as lethargy, fever, or loss of appetite are further causes for immediate veterinary attention. If household members report transient, intensely itchy rashes where they touched the dog, mention that to your vet because sarcoptic mites can provoke brief human irritation even though they don’t complete a life cycle on people.

If you suspect mange: immediate steps for dog owners

1. Isolate the affected dog from other animals and limit close human contact until you have a veterinary plan—this helps reduce spread and protects vulnerable household members.
2. Schedule a veterinary exam promptly. Your veterinarian will likely perform skin scrapings, sometimes repeated or deeper scrapes, and may consider cytology or other tests to look for bacteria, yeast, or mites. Because Demodex can be hard to find on a single scraping, expect the vet to consider the whole clinical picture.
3. Follow the prescribed treatment exactly and complete the full course—even if signs improve quickly—because mites can persist and recrudesce if therapy is stopped too soon. Treatments may include topical medicines, oral antiparasitics, medicated baths, and management of secondary infections.
4. Keep a photographic record and notes on symptoms (timing, areas affected, any new signs). I advise owners to photograph lesions weekly; this helps your vet judge progress and decide whether additional diagnostics or a change in therapy is needed.

Household cleanup and prevention — bedding, grooming, and sanitation

• Wash all bedding, blankets, soft toys, and the dog’s clothing in the hottest water safe for the fabric and dry on high heat when possible. Heat helps kill mites and eggs that are off the dog.
• Vacuum floors, rugs, upholstery, and car seats thoroughly and frequently; focus on crevices and under cushions where fur and debris collect. Discard vacuum bags or empty canisters away from living areas.
• Limit contact between the infected dog and vulnerable animals (puppies, elderly pets, immunocompromised animals) until your vet clears the household. Your veterinarian may recommend treating cohabiting pets preventively depending on the type of mange and the risk assessment.

Treatment essentials: supplies and products vets commonly use

• Veterinarian-recommended medicated shampoos, topical spot-on treatments, or systemic medications—only use products your vet prescribes, since strength and safety differ between formulations.
• Disposable gloves and towels for bathing and handling the affected dog, plus a set of dedicated grooming brushes that can be cleaned or disposed of to avoid cross-contamination.
• A fine-tooth comb can help you monitor for scales, crusts, and debris; a simple digital thermometer and a camera or smartphone for documenting lesions are also useful tools during treatment and follow-up.

Recovery timeline and next steps if your dog isn’t improving

With appropriate diagnosis and sustained treatment, sarcoptic mange is often rapidly controlled and highly treatable; itch may begin to improve within days and lesions within a couple of weeks, though full hair regrowth can take longer. Demodectic mange can be more variable—localized cases in young dogs often resolve as the immune system matures, while generalized or adult-onset forms may require longer courses and investigation for underlying causes.

If there’s little improvement within the timeframe your veterinarian sets, or if the dog develops new systemic signs, worsening odor, or spreading skin damage, return to your vet for re-evaluation. Additional diagnostics to look for bacterial cultures, hormonal issues, or immune suppression may be helpful. I find that owners who keep clear records and photos make it easier to find the right next step when a case is stubborn.

Sources and further reading

• Merck Veterinary Manual: “Sarcoptic Mange (Scabies) in Dogs”
• Merck Veterinary Manual: “Demodicosis (Demodectic Mange) in Dogs”
• American Veterinary Medical Association (AVMA): “Sarcoptic Mange in Dogs — Client Information”
• Centers for Disease Control and Prevention (CDC): “Scabies — Sarcoptes scabiei and Zoonotic Scabies”
• Cornell University College of Veterinary Medicine: “Sarcoptic Mange (Scabies) in Dogs — Factsheet”