Demodectic mange in dogs (also called demodicosis or "red mange") is caused by a tiny mite that almost every dog already carries. It shows up as patches of thin hair or bald skin, most often in puppies, and French Bulldogs get it more than most breeds. The reassuring part: it is not contagious to people or other healthy dogs, and modern treatment works very well.
Is demodectic mange contagious to humans?
No. This is the first question most owners ask, and the answer is reassuring. Demodex mites live inside the hair follicles of almost all dogs without causing trouble. Puppies pick them up from their mother while nursing, within the first 72 hours of life.[1] The disease is not an infection your dog "caught." It is an overgrowth that happens when the immune system can't keep the mites under control.
VCA states that demodectic mange is not contagious to other animals or to people, and that a healthy dog is not at risk from contact with an affected one.[2] You don't need to keep your puppy away from the family or from your other dog.
Don't confuse it with sarcoptic mange (scabies). That is a different mite and a different disease, and sarcoptic mange is contagious, including to people.[2] Your vet can tell them apart, for example with deep skin scrapings.[2]
Demodectic mange symptoms: what it looks like
Vets describe two forms:
| Form | What you see | What usually happens |
|---|---|---|
| Localized | 1 to 5 small, well-defined patches of hair loss with red, scaly skin, mainly around the lips, around the eyes and on the front legs. Itching is mild or absent.[1] | Most common in young dogs, especially those under 6 months. Often clears without treatment in 6 to 8 weeks.[4] |
| Generalized | Many bald areas, inflamed skin, crusts and often a secondary bacterial skin infection, which can itch and smell. | Needs treatment. The juvenile form usually appears between about 2 and 18 months of age.[4] |
A useful clue: demodectic mange usually does not itch unless a secondary infection is present.[2] If your dog is scratching hard, your vet will also look for fleas, allergies or sarcoptic mange. In blue or fawn Frenchies, thinning hair can also come from a genetic coat condition; see our guide to blue French Bulldog hair loss.
Why French Bulldogs are prone to it
A Royal Veterinary College study looked at UK primary-care vet records from 2013. Juvenile-onset demodicosis (before age 2) affected 0.48% of all dogs. In French Bulldogs the figure was 1.88%, about 5 times the odds of mixed breeds. None of the 295 adult French Bulldogs in the study developed adult-onset disease.[3]
Other bull-type breeds also ranked high. The English Bulldog had the highest prevalence of any breed (3.56%), and Pugs had figures close to Frenchies. The authors suggest these related breeds may share a genetic basis, but they present this as a hypothesis, not a proven fact.[3]
In practice: if you have a Frenchie puppy, check the face and front legs during your regular handling sessions, and show any bald patch to your vet early.
Demodectic mange in adult dogs
When demodectic mange appears for the first time in an adult dog (usually after age 4), it is a signal to look for an underlying problem.[4] The Merck Veterinary Manual links adult-onset cases with conditions that weaken immunity, such as:[1]
- Hypothyroidism
- Cushing's disease (hyperadrenocorticism)
- Diabetes
- Some cancers
In many dogs no cause is ever found.[1] Long-term steroid treatment can also trigger it, so the European parasite council (ESCCAP) advises avoiding steroids in these dogs.[4] Expect your vet to suggest blood tests alongside the skin treatment.
Demodectic mange in dogs: treatment
Diagnosis comes first. Your vet takes deep skin scrapings and looks for mites under the microscope; occasionally a biopsy is needed.[2]
- Isoxazolines are now the treatment of choice for generalized disease. These are the same active ingredients found in many oral flea and tick products (afoxolaner, fluralaner, sarolaner, lotilaner). Your vet chooses the product and schedule.[1][2]
- Dips and shampoos: amitraz dips and benzoyl peroxide shampoos are used much less than before.[2] A medicated shampoo may still help with secondary skin infection, but it is not the cure.
- How long: treatment continues until the skin looks normal and at least two skin scrapings in a row, one month apart, are negative.[1] A dog is considered cured only if there is no relapse within 12 months after treatment ends.[4]
- Relapses can happen up to about 12 to 18 months of age.[2]
Is there a treatment at home? Not one that works on its own. Oils, vinegar or sulfur products found online don't reach mites deep in the follicles and can irritate the skin. What you can do at home is give the prescribed medicine on schedule, keep follow-up scraping appointments, and keep your puppy well fed and low-stress.
What it means for breeding and buying a puppy
Veterinary sources agree that dogs with juvenile generalized demodectic mange should not be bred. Merck calls this the only preventive measure available.[1] VCA goes further and advises not breeding the parents of an affected dog again.[2]
If you are choosing a Frenchie puppy, it is fair to ask the breeder whether previous litters had demodectic mange. Our French Bulldog breeder health tests guide and puppy health checklist cover what else to ask.
Sources and references
- Dryden MW. Mange in Dogs and Cats [Internet]. Merck Veterinary Manual; 2023 Mar [updated 2025 May; cited 2026 Nov 3].
- Weir M, Panning A, Ward E. Demodicosis (Demodectic Mange) in Dogs [Internet]. VCA Animal Hospitals; [date unknown] [updated 2026 Jun 12; cited 2026 Nov 3].
- O'Neill DG, Turgoose E, Church DB, Brodbelt DC, Hendricks A. Juvenile-onset and adult-onset demodicosis in dogs in the UK: prevalence and breed associations. Journal of Small Animal Practice. 2020;61(1):32-41. doi:10.1111/jsap.13067.
- European Scientific Counsel Companion Animal Parasites. Control of Ectoparasites in Dogs and Cats. ESCCAP Guideline 03, Seventh Edition [Internet]. ESCCAP; 2022 Jan [cited 2026 Nov 3].