The black spots that start to develop on dogs’ bodies are usually a sign of hyperpigmentation and are totally harmless. Some dogs are born with them, while others may develop them along the way. Black spots can also have medical causes. The most common are bacterial and fungal infections, allergies, or certain internal diseases.
Has your dog’s skin become darker in a certain area? Or does your dog have black spots on its belly or back?
Most of the time, the appearance of black spots on dogs’ skin is not something to worry about. The most common and harmless is hyperpigmentation, which can appear for various reasons.
In this article, you will learn why black spots appear on your dog’s skin, what the most common causes are, what dog breeds are more prone to developing them, and more.
Why Does My Dog Have Black Spots on His Skin?
The most common cause of black spots on dogs’ skin is hyperpigmentation. Dogs can be born with these spots or they can develop them with time. Hyperpigmentation spots are harmless when they are not accompanied by other symptoms. In other situations, these black spots on dogs’ skin are the symptom of a medical condition.
Dogs can be born with black spots on their skin, but they can also acquire them as they age.
These spots are in most cases the result of hyperpigmentation and usually appear in the following places:
- Abdomen
- Groin area
- Tail
- Back
Hyperpigmentation occurs when too much melanin is produced in the skin. Melanin is the pigment that gives color to the coat, eyes, and skin.[1]
It usually affects the skin of dogs, but can also affect their nails and fur.
Harmless black spots on dogs’ skin are flat and have the same texture as the rest of the skin.
Contact your veterinarian if these dark spots are accompanied by the following changes and symptoms:
- Intense itching and scratching
- Hair loss
- Bleeding
- Crusts
- Bumps filled with fluid
- Prominent lumps
- Thickened skin
- Weight loss
- Enlarged abdomen
Related: Dog Has Black Spots & Losing Hair
Why Does My Dog Have Black Spots on His Belly?
Black spots on dogs’ bellies appear for approximately the same reasons as those on the rest of the body. Most are pigment spots that do not endanger your dog’s life. Other causes of black spots on your dog’s belly are allergies, yeast infections, or Cushing’s disease.
Black spots on dogs’ bellies are caused by the same things as those on the rest of the body. Most of them are pigment spots.
Dogs can be born with these black spots on their bellies. They can also appear as a reaction to various skin conditions or internal diseases.
The most common causes for black hyperpigmentation spots:
- Old age
- Friction
- Sun exposure
These black spots on the stomach can also occur because of the following health conditions or internal diseases:
- Hypothyroidism
- Mange
- Cushing’s disease
- Food allergies
- Yeast infections
- Flea allergy dermatitis
- Epidermal hamartoma
Common Causes for Black Spots on the Skin
The most common cause for the appearance of black spots on the skin of dogs is hyperpigmentation.
Hyperpigmentation can occur as a result of:
- Exposure to the sun: Spots especially appear on the stomach and other hairless areas.
- Aging: Spots can appear all over the body.
- Friction: Spots especially appear in the armpits and between the legs in dogs that wear clothes.
Another cause for the appearance of brown or black spots on the skin of dogs is acanthosis nigricans. This is also a type of hyperpigmentation.[2]
True acanthosis nigricans occurs mainly in Daschunds where clinical signs often appear by the age of one year.
Secondary acanthosis nigricans is a post-inflammatory hyperpigmentation that generally occurs in breeds prone to inflammation in the armpits and groin area. It can appear at any age and breed.
The causes for secondary acanthosis nigricans are:
- Conformation anomalies.
- Obesity.
- Endocrine diroders (hypothyroidism, hyperadrenocorticism, sexual hormone disorders).
- Atopic dermatitis that manifests with itching in the axillary and groin area.
- Contact dermatitis.
- Allergies.
- Primary keratinization disorders (a physiological process of the epidermis that allows it to form its outermost layer[3]).
- Skin infections (with Staphylococcus or Malassezia).
- And others.
What Breeds Have Black Spots on Their Skin?
Some dog breeds are born with spots on their skin, including American Hairless Terriers, Bluetick Coonhounds, Chihuahuas, Dalmatians, Great Danes, Jack Russell Terriers, and more. The color, size, and shape of the spots vary from breed to breed and from individual to individual.
The skin of dogs is generally one color. But, there are breeds that are born with spotted skin.
The following breeds can all be born with spots (though these vary in color, size, and shape): [4]
- American Hairless Terrier
- Bluetick Coonhound
- Brittany spaniel
- Catahoula Hound
- Chihuahua
- Dalmatian
- Great Dane
- Jack Russell Terrier
- Staffordshire terrier
The hyperpigmentation that appears later in life is usually obvious in dogs with white or light fur and hairless dogs.
Medical Conditions That Cause Black Spots
Several medical conditions can cause the appearance of black spots on the skin of dogs. The most common are infections, allergies, or internal diseases.
In addition to hyperpigmentation due to age, friction, or exposure to the sun, black spots on the skin can also appear as symptoms of medical conditions.
Some are hyperpigmentation spots, while others can be bruises, residues, or abnormal skin growths.
The most common medical conditions that cause black spots on the skin of dogs are:
- Bacterial infections
- Fungal infections
- Yeast infections
- Cutaneous vasculitis
- Endocrine disorders (hypothyroidism, Cushing’s disease)
- Alopecia X
- Allergies
- Cancer (melanoma)
- Epidermal hamartoma
Bacterial, Fungal, and Yeast Infections
Bacterial and fungal infections can be a primary condition or occur as a result of allergies when dogs scratch excessively.
Dirt on their feet, humidity, and non-hygienic environmental conditions usually speed up the development of bacteria and fungi on dogs’ skin.
Other times, black spots on dogs’ skin can look like dirt, in which case they are usually an indication of yeast infections. These black or brown spots are usually flat and initially develop in the groin area.
Other areas where spots can appear as a result of these conditions:
- Between the toes
- The ear canal
- The anal and rectal area
- The vaginal area
Regardless of the type of infection, they are accompanied by symptoms:[5]
- Intense itching
- Redness of the skin
- Bad smell
- Scabs on the skin
- Excessive licking of the affected area
- Hair loss
Cutaneous Vasculitis
Cutaneous vasculitis is a medical condition where the walls of the small vessels of the skin become inflamed.[6] These small vessels can break and bleed under the skin, showing as black spots of various shapes and sizes.
These black spots are nothing but bruises. Over time, the bruises change color until they turn yellow and disappear.
Endocrine Disorders
The endocrine system is the one that produces hormones. Endocrine disorders refer to medical conditions in which this endocrine system does not function properly.
Two of the most common endocrine disorders in which black spots can appear on the skin of dogs are:
- Hypothyroidism
- Hyperadrenocorticism (Cushing’s disease)
Hypothyroidism
Hypothyroidism is an endocrine condition most often associated with immune-mediated thyroiditis or idiopathic thyroid atrophy. It is represented by the reduction in the production of thyroid hormones T3 and T4.
Castrated animals (females and males) have a higher risk of developing it. The most affected breeds are the Golden Retriever, Doberman Pinscher, and Beagle.
Clinical signs are numerous, but not very specific. Dogs can show dermatological, cardiovascular, and/or nervous signs.
Dermatological signs include:
- Dry skin
- Hair loss (usually symmetrical (bilateral) and appears initially on the sides of the trunk, lower chest, and tail)
- Hyperkeratosis (thickening of the skin).
- Hyperpigmentation (black spots).
- Recurrent otitis.
Cushing’s disease
Cushing’s syndrome or hyperadrenocorticism is one of the most common endocrine disorders in dogs. It consists of an increased concentration of cortisol in the blood. Cortisol is a hormone produced by the adrenal glands.
This disorder mainly affects individuals over six years of age, although some cases have also been found in younger dogs.
Among the most predisposed dog breeds are Dachshund, Boston terrier, Poodle, Boxer, and Beagle.[7]
The symptoms are varied and include:
- Excessive thirst
- Excessive urination
- Increased appetite
- Weight gain
- Swollen abdomen
- Obesity
- Hair loss – symmetrical on the sides of the abdomen
- Lack of energy
- Skin irritations
- Thinning of the skin
- Hyperpigmentation (black spots)
Alopecia X
Alopecia X is a genetic condition that tends to affect especially males of the northern breeds: Pomeranians and Alaskan Malamutes. The cause of the disease is generally considered to be a hormonal imbalance.
This condition is also called black skin disease or pseudo-Cushing, and symptoms include:
- Hair loss
- The appearance of black spots (hyperpigmentation)
- Skin with a crusty appearance
Allergies
Allergies can cause brown or black spots on the skin. Food allergies and flea allergy dermatitis are the most common allergies that can result in black spots on dogs’ skin, including the belly.
Other symptoms include:
- Excessive licking of the affected area
- Excessive itching and scratching
- Hair loss
- Bad skin odor
- Crusts on the skin
Cancer
Skin cancer (melanoma) can manifest as black spots. Melanoma is a form of cancer that occurs when melanin-producing cells (melanocytes) multiply a lot.
It can be benign (melanocytoma) or malignant, the most dangerous for the animal’s life being the malignant one.
Melanomas occur most frequently:
- In the mouth
- On the lips
- On the gums
You can also find them in areas with or without hair, but less often.
This type of cancer is dangerous because it metastasizes (spreads) extremely quickly in other organs.
The most predisposed breeds are Schnauzer and Scottish terrier.
Melanocytoma (the benign form) is generally found in hairy areas and appears as a dark mass. They are small and grow slowly compared to malignant melanoma, which spreads extremely quickly on the skin.
They appear most often in old dogs, and the most prone breeds are:
- Schnauzer
- Vizsla
- Doberman Pinscher
- Terriers
- Labrador Retriever
Epidermal Hamartoma
Epidermal hamartoma also known as nevi is a type of benign tumor that appears on the skin of dogs. This condition most commonly affects the cocker spaniel breed, but it can also affect other breeds. These formations look like sharp pigmented plaques and are prone to secondary bacterial infections if they are not treated in time.[8]
