Belly rubs and petting are some of the best ways to bond with your dog, and they help you get familiar with your dog’s skin and coat. If you notice dark patches or changes in your dog’s skin color or texture, you might wonder what’s going on. Hyperpigmentation in dogs is common and can have several causes. Understanding what’s normal and when to see your veterinarian can help you keep your dog happy and healthy.

Understanding Your Dog’s Hyperpigmentation

Hyperpigmentation is the term used when a dog’s skin becomes darker and thickened. It can be localized (in one specific area), multifocal (in several localized areas), or generalized (all over).

The skin texture will be thicker and feel velvety or rough. The color can be light brown to black depending on the severity. The color change occurs due to the skin producing an increased skin pigment called melanin. It’s often noted on hairless folded skin areas such as the armpits, underbelly, groin, and inner thighs.

Hyperpigmentation is not a diagnosis or disease but rather a reaction or secondary change of the body to another condition.

What Are the Causes of Hyperpigmentation in Dogs?

Dogs of all breeds, ages, and coat types can be affected by hyperpigmentation. It can be primary or secondary.

Primary Hyperpigmentation

This is due to a primary disease such as a genetic disorder called Acanthosis Nigricans. It’s especially prevalent in Dachshunds, but any breed can be affected1. Typically, this type of hyperpigmentation is evident by the time a dog is one year of age and affects primarily the armpits and upper front legs.

Primary vs. Secondary Hyperpigmentation

Secondary Hyperpigmentation

This can result from any chronic or ongoing condition that causes trauma, inflammation, and/or friction to the skin.

Causes of secondary hyperpigmentation in dogs include:

• Skin allergies

• Skin infections

• Skin parasites that cause inflammation, such as demodicosis

• Chronic itching, licking, or biting of the skin

• Hormonal disorders like Cushing’s disease (hyperadrenocorticism) or hypothyroidism

• Systemic lupus erythematous (autoimmune disease)

• Malassezia dermatitis, a yeast infection of the skin

• Medications

• Psychological issues that lead to self-trauma such as acral lick granulomas

• UV exposure

Any breed can be affected by secondary hyperpigmentation, but it is more prevalent in breeds prone to allergies, skin infections, hormonal imbalances, and obesity.

The skin of hairless breeds, like the Chinese Crested or Mexican Hairless, tends to be darker naturally since it’s exposed to the elements and less protected than breeds with thicker coats. Sun avoidance and protection is important for hairless dogs, or for those who like to sunbathe to prevent skin irritation and the development of skin cancer.

Diagnosing Hyperpigmentation in Dogs

Hyperpigmentation treatment depends on identifying the underlying cause. To make a diagnosis, your veterinarian will need a detailed medical history of your dog. They may ask:

• What other signs have you noticed?

• How long have the signs been present?

• When do they occur most often?

• What other changes have you noticed?

• Any environmental changes?

• What food/treats (protein source) does your dog eat?

• Is your dog on any medications or supplements?

They will also perform a full physical examination of your dog and run diagnostic tests such as: blood work and blood chemistry, urinalysis, skin scrape (a sample of skin layers to detect parasites,) or skin cytology (to detect bacteria and yeast overgrowth).

Advanced diagnostic tests may be needed for such diseases as Cushing’s disease or hypothyroidism. Skin biopsies may be needed if first-line diagnostic tests do not give a diagnosis.

After your veterinarian has identified the underlying cause of the hyperpigmentation, they can formulate a treatment plan for your dog.

How to Treat Primary Hyperpigmentation in Dogs

Primary hyperpigmentation has no cure, but the signs can be managed when detected early enough. For some dogs, it can be completely cosmetic, and no treatment is needed. For others, treatments may include steroid, antibiotic or antifungal creams/ sprays or mousses, and medicated shampoos. Additional treatment may be necessary for cases that worsen.

How to Treat Secondary Hyperpigmentation in Dogs

It's important for dog owners to realize that resolution of hyperpigmentation is a slow process. It can take months before the skin color returns to normal.

Treatment, depending on the cause, can include:

• Food trials

• Antifungal medications

• Antibiotics

• Medicated shampoos

• Allergen Immunotherapy

• Medications to treat specific diseases such as hypothyroidism or Cushing’s disease

• Sun protection

Secondary hyperpigmentation can re-occur if the underlying cause is not properly treated and managed.

By staying alert to changes in your dog’s skin and partnering with your veterinarian, you can help your dog stay comfortable and healthy. If you notice dark patches or thickened skin, schedule a checkup to get to the bottom of it and keep your pet feeling their best.