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My Dog Has Black Spots on Its Skin and Its Losing Hair: Why Is This Happening?

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Black spots on dogs’ bodies and hair loss mainly occur for three reasons: parasites, allergies, and skin infections. The most common parasites that can cause black spots and hair loss in dogs are mange-transmitting mites. Other conditions that can cause black bald spots on dogs include Alopecia X, Cushing’s syndrome, and hypothyroidism.

The development of black spots on the dogs’ bodies is not usually a cause for concern. They often appear due to old age or prolonged sun exposure.

But, black spots should be a cause of concern when they are accompanied by other symptoms, such as hair loss, bleeding, or crusting. 

If this is the case, your dog most likely suffers from a medical condition that needs to be treated, and a trip to the vet is necessary.

In this article, you will learn why dogs develop black spots on their skin and their hair falls out, how to recognize medical conditions, and what you should do.

Causes for Dark Spots on Dogs’ Skin With Hair Loss

The most common cause of black bald spots on dogs’ skin are parasites, allergies, and various diseases. Take your dog to the vet if the black spots start to go bald.

Hair loss and the development of black spots on dogs’ skin are two clinical signs that can occur in the following medical conditions:

  • Parasitism
  • Allergies
  • Skin infections
  • Alopecia X
  • Internal disease

In some medical conditions, these symptoms are accompanied by intense scratching.

In the case of sarcoptic mange (which causes intense itching and scratching) your dog can even transmit it to other pets and humans.

Other diseases (such as Cushing’s syndrome and hypothyroidism) won’t make our dog itch, but they are more severe and can cause major dysfunctions in your dog’s body.

Because of this, it is best to take your pet to the vet when you see bald black spots on its body.

Parasitism

Parasitism on dogs
Image Source

Two species of mites cause hair loss and the appearance of black spots. The mites themselves don’t cause this. Instead, they transmit two types of mange:

  • Demodicosis caused by Demodex canis.
  • Sarcoptic mange cause by Sarcoptes scabiei.

Demodicosis

Canine demodicosis is a parasitic skin disease caused by the mite Demodex canis, D. injai[1], or D. cornei[2]

These parasites are microscopic. They latch onto the hair roots (hair follicles) and sebaceous glands, quickly growing and developing. They mainly parasitize young dogs.

The disease is transmitted from other dogs in two ways:

  • Direct contact of young puppies with their mother, in the first hours of life, 
  • Direct contact with other sick dogs.

Demodicosis evolves in two forms, and the clinical signs appear after approximately 6-8 weeks from direct contact:

  • Dry form (simple)
  • Wet form (suppurative)
Dry form or localized form

Dogs affected by the dry or localized form of demodicosis show the following symptoms:

  • Reddish areas on the head and face (around the eyes, at the edge of the lips, on the cheek, at the base, and on the ears), on the limbs, on the neck, chest, and abdomen.
  • Fine, yellowish-white scales that come off easily.
  • Excess of oily secretions on the skin, which gives dogs a repulsive smell.
  • Hairless areas, especially around the eyes (“demodectic glasses”) and lips, but also on the head, chest, and limbs.
Wet form or generalized form

Dogs affected by the wet or generalized form of demodicosis show the following symptoms:

  • Inflamed skin.
  • A repulsive smell of “rancid butter”.
  • White-yellowish or purple pustules appear that contain pus.
  • Intense scratching that causes bleeding.
  • The lesions extend over the entire surface of the body.
  • The skin is thickened and becomes similar to tree bark.
  • Progressive weight loss.
  • Renal complications leading to your dog’s death (in severe cases).

Sarcoptic Mange

Sarcoptic Mange in Dogs
Image Source

Sarcoptic mange is a skin condition caused by Sarcoptes scabiei mites. It can occur in all breeds of dogs, regardless of size or age. 

It most frequently occurs during the winter and spring in the following dogs:

  • Malnourished dogs with poor hygiene.
  • Pregnant or lactating females.

The disease is transmitted from one animal to another or from the environment, where the parasites can survive 15 days to four weeks. 

Sarcoptic mange is also transmitted to humans.[3]

The incubation period is 14-21 days, and the symptoms include:

  • Intense itching and scratching – dogs scratch to the point of self-mutilation.
  • Rashes all over the body – initially they appear on the muzzle, around the eyes, on the chest, and abdomen.
  • Hair loss
  • Weight loss
  • Death

In cases where the lesions are generalized, the crusts may appear dark like black spots on the skin.

Allergies That Cause Black Spots and Hair Loss

Allergies That Cause Black Spots and Hair Loss

Dogs can be allergic to many things:

  • Drugs
  • Food
  • Fleas
  • Pollen or other substances from the environment
  • Toxins

The symptoms of allergies generally include the following:

  • Intense scratching
  • Hair loss
  • Red lesions on the skin that occur after scratching
  • Dry skin and crusts

In some cases, the skin in the hairless areas can become dark or black.

Flea allergy dermatitis

Flea allergy dermatitis is not a medical condition that endangers pets’ life. But, it causes a lot of discomfort. 

This condition is an exaggerated allergic reaction of the immune system. It is triggered when the immune system comes in contact with some of the components of flea saliva.

The most predisposed dogs are those that come into occasional contact with these external parasites. Dogs with massive flea infestations develop a tolerance to their saliva over time.

There is no predisposition to species, breed, age, or sex. All dogs can develop allergies.

Symptoms of this type of allergy include:[4]

  • Intense itching and scratching
  • Hair loss
  • Red, inflamed skin
  • Small brown spots that look like dirt (flea feces)

Skin Infections That Cause Black Spots and Hair Loss

Skin Infections That Cause Black Spots and Hair Loss

Skin infections are caused by:

  • Bacteria
  • Fungi
  • Yeast

Breeds with long hair or many skin folds are more prone to developing skin infections. These infections are often the result of excessive scratching associated with allergies.

Before going to the vet, make sure your dog has a skin infection and isn’t merely affected by other things that look like skin infections:

  • Dirt
  • Humidity
  • Non-hygienic conditions

If your dog has a yeast infection, it’ll look dirty. The blackish-brown spots initially appear in the groin area and spread to other regions:

  • The ear canal.
  • Between the toes.
  • In the vaginal and anal areas.
  • Skin infections symptoms include:[5]
  • Intense itching
  • Excessive licking of the affected area
  • Inflamed skin
  • Bad odor
  • Dark scabs on the skin
  • Hair loss

Black Spots and Hair Loss From Alopecia X

Alopecia in dogs
Image Source

Alopecia X or black skin disease is a skin condition where dogs’ hair falls out due to non-inflammatory causes. 

This condition is also called “pseudo Cushing’s”. It causes the hair cycle to stop, resulting in hair loss.

Some breeds are more prone to alopecia X[6] than others:

  • Pomeranian
  • Malamute
  • Schipperke
  • Samoyed
  • Chow Chow
  • Miniature poodle

This condition is not predisposed to sex or age and can appear both in neutered and intact dogs.

Alopecia X has no cure, but there is still hope. Studies have shown that hair growth can start again in dogs treated with low-level laser therapy (LLLT) for two months twice a day.[7]

Internal Diseases That Cause Black Spots and Hair Loss 

Cushing’s Disease
Image Source

The following medical conditions can cause hair loss and the appearance of black spots on dogs:

  • Cushing’s syndrome
  • Hypothyroidism

Cushing’s syndrome

Cushing’s syndrome is an endocrine (hormonal) condition in which the adrenal glands produce an excess of hormones.

Dogs affected by this typically get sick around the age of 6-7 years. Cushing’s syndrome can appear anytime between the age of two and 16. 

The most affected breeds are:[8]

  • Dachshund
  • Boxer
  • Poodle
  • Boston terrier
  • Beagle

The disease is complicated and includes both specific and non-specific symptoms:

  • Excessive thirst and urination (the most common symptoms)
  • Symmetrical hair loss on the sides of the abdomen (occurs in 50-90% of cases)
  • Swollen abdomen (occurs in 80% of cases)
  • Black spots on the skin (hyperpigmentation)
  • Increased appetite
  • Weight gain
  • Skin irritations
  • Thinning of the skin
  • Obesity
  • Apathy
  • Panting
  • Recurrent urinary infections

Hypothyroidism

Hypothyroidism is a disorder of the thyroid gland. In hypothyroidism, the thyroid is underactive and cannot secrete enough T3 and T4 thyroid hormones.[9] This lowers dogs’ metabolism.

While there is a genetic predisposition to thyroid disorders, environmental factors and thyroid cancer also play a role in their development.

There is no gender predisposition. Hypothyroidism can also affect intact or neutered dogs.

Hypothyroidism has various non-specific symptoms that include:[10]

  • Dogs show no interest in playing.
  • They sleep frequently.
  • Fatigue from long walks.
  • Weight gain.
  • Chronic ear infections.
  • Bacterial skin infections.
  • Dry skin.
  • Hair loss, especially on the trunk and tail.
  • Discoloration and/or thickening of the skin where the bald spots occurred.
  • Hyperpigmentation (black spots on the skin).
  • Slow heart rate.
  • Unprovoked aggression.
  • Head tilt.
  • Anxiety.
  • Seizures.
  • Depression.

What to Do if Your Dog Has Black Spots on Its Skin and Losing Hair

Contact the veterinarian if your dog has black spots accompanied by other symptoms (such as hair loss). The causes for these two symptoms are multiple, and some of them are life-threatening.

There’s probably no reason to panic if your dog only shows black spots on the skin without hair loss or other associated symptoms. In this case, the black spots are most likely caused by old age or sun exposure.

About Iulia Mihai (DVM)

Dr. Iulia is a certified veterinarian with more than 10 years of experience in the field. With extensive knowledge of diet, care, and medication, she helps Misfit Animals provide readers with accurate knowledge on technical topics.

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