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Black Skin in Dogs (Hyperpigmentation)

By the Dog Health Handbook team · Updated · Fact-checked against current veterinary references (see sources)

Key takeaways

  • Black skin is a reaction, not a disease.
  • Common causes: allergies, yeast, friction and hormone disease.
  • Alopecia X is also called black skin disease.
  • A raised or bleeding dark lump should be checked for melanoma.
  • Darkening fades slowly once the cause is treated.

Table of Contents

Research Causes Appearance Melanoma Diagnosis Treatment FAQ Sources

Skin Infections and Coat Problems Quicklinks

Skin Infections Pyoderma (Staph) Yeast Infections Pimples and Bumps Dry Skin Dandruff Seborrhea Hair Loss Black Skin

Black skin in dogs (hyperpigmentation) is a darkening, and often thickening, of the skin. It's a reaction to another problem, not a disease in itself.1,2 Merck notes that "the presence of secondary hyperpigmentation always suggests an underlying disease."1 The most common triggers are chronic allergies, yeast (Malassezia) and staph infections, friction in skin folds or from obesity, and hormone diseases such as hypothyroidism and Cushing's disease.2 Darkened skin with hair loss in Pomeranians and other plush-coated breeds may be alopecia X, also called "black skin disease."3 A rare inherited form, primary acanthosis nigricans, occurs almost only in Dachshunds.2 Most secondary darkening fades once the cause is treated, though it can take months.1,2 A raised, growing or bleeding dark lump is different and should be checked for melanoma.4,5

See your vet if your dog has:

  • A raised, growing, ulcerated or bleeding dark lump, or a dark spot on the lips, in the mouth or at a nail bed4
  • A swollen toe or a lost nail in an older dog4
  • Dark skin with itching, odor, greasy skin or red edges, which can mean infection1,2
  • Darkening skin with hair loss, weight gain, tiredness or increased thirst2,6

What the Research Says

  • Allergy alone can darken skin. In a 2022 experimental study, applying house dust mite allergen to dogs' skin caused redness, darkening and thickening.7
  • Yeast is often involved. A 2025 study found Malassezia yeast on cytology in 47 dogs with signs including darkened, thickened skin.8
  • Skin folds matter. In a 2022 UK study of more than 900,000 dogs, English Bulldogs were about 49 times more likely than crossbreeds to have skin-fold dermatitis, and French Bulldogs and Pugs were also at high risk.9
  • Hormone tumors can cause it. In a 2023 report of 7 dogs with Sertoli cell testicle tumors, hair loss and darkened skin resolved within 2 months after surgery.10

Causes of Black Skin

  • Allergies: atopic dermatitis, food allergy and contact allergy, often on the belly, armpits and legs2,11
  • Yeast and staph infections2,12
  • Friction: skin folds, obesity and body shape2
  • Hypothyroidism: darkened skin with non-itchy hair loss and a dull coat13
  • Cushing's disease and sex hormone problems2,10
  • Alopecia X: hair loss with dark skin in Pomeranians, Chow Chows, Keeshonds, Siberian Huskies and other plush-coated breeds3,6
  • Seasonal flank alopecia: dark, hairless flanks in Boxers, Bulldogs and Airedales, mostly in winter14
  • Scaling disorders (seborrhea)2,15
  • Primary acanthosis nigricans: an inherited form in Dachshunds, starting by about 1 year of age in the armpits or groin2

What It Looks Like

Darkening often starts as lacy or patchy areas and can progress to thick, leathery, hairless skin.2 Merck describes it as light-brown-to-black, "velvety, rough areas of thickened, often hairless skin," most often on the legs and groin. Red edges can mean a bacterial or yeast infection.1 Darkening linked to hormone disease is usually not itchy.2

Is It Melanoma?

Benign pigmented growths (melanocytomas) are diagnosed much more often than malignant melanoma. Melanocytomas are usually single, pigmented spots or growths, mostly on the head and front legs.4 Malignant melanomas are most common on the lips, in the mouth and at the nail beds, and often look raised and ulcerated. A swollen toe in an older dog can be a warning sign.4 Any dark lump should be checked with a needle sample.16,5

Diagnosis

Vets use skin scrapings for mites, cytology and cultures for bacteria and yeast, and allergy testing or diet trials.1,2 Because darkening caused by hormone disease isn't usually itchy, older dogs with non-itchy black skin should be screened for thyroid and adrenal disease.2 A biopsy may be done in unusual cases.1

Treatment

  • Treat the cause, such as allergy, infection or hormone disease.2,1
  • Treat yeast and bacteria with medicated shampoos and sprays, and with antifungal or antibiotic pills when needed.2
  • Reduce friction with weight loss and emollients.2

Most darkening fades once the cause is controlled, though slowly, and some lacy pigment may remain. Primary acanthosis nigricans in Dachshunds can't be cured, but it may stay cosmetic.2

Frequently Asked Questions

Why is my dog's skin turning black?

Usually because of chronic allergy, infection, friction or hormone disease.

Will my dog's black skin go away?

Often, once the cause is treated, but it can take months.

Is black skin on dogs serious?

The darkening itself isn't, but it's a sign of an underlying problem that needs attention.

Why is my dog's belly turning black?

Allergies, yeast and friction are common causes. Hormone disease is possible in older dogs.

What is black skin disease?

A common name for alopecia X, a non-itchy hair loss with dark skin in plush-coated breeds.

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Sources and further reading

This article was rewritten and fact-checked on October 23, 2026 against current veterinary references and specialist guidelines:

  1. Moriello KA. Hyperpigmentation (Acanthosis Nigricans) in Dogs. Merck Veterinary Manual (pet owner version), updated September 2024.
  2. Moriello KA. Primary Acanthosis Nigricans and Postinflammatory Hyperpigmentation in Dogs. Merck Veterinary Manual, updated January 2025.
  3. Barnes C. Alopecia X in Dogs. VCA Animal Hospitals, updated September 2026.
  4. Villalobos AE. Tumors of Melanocytic Origin in Animals. Merck Veterinary Manual, updated November 2024.
  5. MSPCA-Angell. Lumps and Bumps: When to Be Concerned. MSPCA-Angell, February 2026.
  6. Apostolopoulos N. Understanding and Treating Canine Alopecic Dermatoses. Today's Veterinary Practice, March/April 2025.
  7. Kim, Kim. Establishing an experimental model for canine atopic dermatitis through epicutaneous application of Dermatophagoides farinae. Frontiers in Veterinary Science, 2022.
  8. Abhijith, Ravishankar, Rajasekhar, et al. Isolation and molecular characterisation of Malassezia pachydermatis from dogs in Kerala. Journal of Veterinary and Animal Sciences, 2025.
  9. O'Neill DG, et al. Ironing out the wrinkles and folds in the epidemiology of skin fold dermatitis in dog breeds in the UK. Scientific Reports, 2022.
  10. Gokulakrishnan, Rasool, Sarath, et al. Testicular tumor and associated clinical, hormonal and hematobiochemical symptoms and its successful surgical management in canines. Exploratory Animal and Medical Research, 2023.
  11. Hoff S. Atopic Dermatitis in Dogs. Merck Veterinary Manual, updated May 2026.
  12. Bond R, Morris DO, Guillot J, et al. Biology, diagnosis and treatment of Malassezia dermatitis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Veterinary Dermatology, 2020.
  13. Cornell Riney Canine Health Center. Hypothyroidism. Cornell University College of Veterinary Medicine.
  14. Torres SMF. Canine Flank Alopecia. In: Small and Large Animal Dermatology Handbook, Vol. 2. University of Minnesota Libraries Publishing, 2025.
  15. Heinrich NA. Seborrhea in Animals. Merck Veterinary Manual, updated May 2025.
  16. Warland J, Dobson J. Canine and Feline Skin Tumors. Veterinary Focus 21(3), 2011 (IVIS).

About this article

Last updated : fully rewritten using the Merck Veterinary Manual, VCA Animal Hospitals, an open veterinary dermatology textbook, IVIS and 2022 to 2026 research, plus International Veterinary Information Service (IVIS) proceedings and research published 2022 to 2026.

This page is for general information and is not a substitute for an exam by your veterinarian.