Dog Losing Hair and Black Spots on Skin (Here’s Why)

Dog Losing Hair Black Spots on Skin: Common Causes

Hyperpigmentation From Chronic Irritation

Hyperpigmentation is one of the most common reasons a dog has hair loss with black spots.

When the skin is inflamed repeatedly — from licking, scratching, allergies, or rubbing — it darkens over time. This darkening may appear as large patches or small spots.

You may notice:
• Thickened skin
• Rough texture
• Slow hair regrowth
• Redness earlier in the condition

Hyperpigmentation itself is harmless, but it means the skin has been irritated for a long time. Finding the underlying cause is essential.

Read more: Dog Losing Hair in Spots (What it means)

Yeast Infection 

Yeast overgrowth often causes dark, greasy, itchy skin and significant hair loss.

Yeast infections commonly affect areas like the armpits, neck, belly, groin, and paws but can spread anywhere. These infections create black or brown patches that feel thick or oily.

Other signs include:
• Musty smell
• Redness between dark spots
• Greasy skin
• Licking or chewing

Yeast infections thrive in moist environments and often accompany allergies. They require antifungal treatment to resolve.

Flea Allergy Dermatitis

Dogs allergic to flea saliva can develop small black scabs, dark patches, and hair loss.

Even one flea bite can trigger widespread itching. Scratching causes hair to fall out and the skin to become darker from repeated irritation.

Typical signs include:
• Bald spots near the tail base
• Speckled black dots or scabs
• Red bumps
• Intense scratching

Consistent flea control is essential to resolving this cause.

Hormonal Disorders 

Endocrine disorders commonly cause hair loss and darkened skin.

Hypothyroidism may cause:
• Thinning hair
• Black patches of hyperpigmentation
• Weight gain
• Dry skin
• Low energy

Cushing’s disease may cause:
• Thin skin
• Slow hair regrowth
• Black spots or dark patches
• Pot-bellied appearance
• Increased thirst and urination

Hormonal imbalances disrupt normal skin turnover and pigment production, causing visible darkening.

Mites 

Mites can create irritation that leads to hair loss and dark, scaly patches.

Demodex mites often cause patchy bald spots with thick, dark skin. Sarcoptic mange causes severe itching, crusting, and blackened areas from self-trauma.

Dogs may display:
• Redness
• Scabs
• Itching
• Scaling
• Odor

Mites are microscopic and require veterinary diagnosis. Some types are contagious.

Folliculitis or Bacterial Skin Infection

Bacterial infections cause hair loss, pustules, scabs, and dark marks where the skin becomes inflamed.

When the infection heals, the skin may remain darkened for weeks or months. Folliculitis often begins as small bumps or pimples that later create black spots.

Dogs with allergies or oily skin are prone to recurring infections.

Read more: Dog Losing Hair on Back End (Causes explained)

What to Do If Your Dog Is Losing Hair and Has Black Spots on the Skin

Begin by examining the affected areas carefully. Look for redness, bumps, flakes, or a greasy texture.

Ensure your dog is on consistent flea prevention — even one bite can cause lasting irritation. Flea allergy dermatitis is often the simplest cause to rule out.

Keep the skin clean and dry. Moisture encourages yeast and bacterial growth.

Use a gentle, fragrance-free shampoo designed for sensitive or medicated skin. Avoid harsh soaps, which can worsen irritation.

Check your dog’s diet. Food sensitivities contribute to itching, inflammation, and hyperpigmentation.

Consider switching to a limited-ingredient or hypoallergenic formula if allergies are suspected. Introduce diet changes slowly.

Prevent licking or scratching by using an e-collar or recovery suit. Constant self-trauma deepens dark spots and delays healing.

Supplement with omega-3 fatty acids (vet-approved). These support the skin barrier and reduce inflammation.

Monitor the black spots closely for changes. Sudden spreading, raised bumps, foul odor, or oozing requires prompt veterinary care.

When to Call or Visit Your Vet

You should seek veterinary help if your dog is losing hair and has black spots and any of the following signs are present:

• If the black spots are growing, spreading, or becoming raised, deeper infection or endocrine issues may be involved. This requires diagnosis.
• If your dog is intensely itchy — biting, licking, or scratching — allergies, mites, or infection are likely. Itching always deserves veterinary attention.
• If there is odor, greasy skin, red borders, or discharge, a yeast or bacterial infection may be present. These conditions rarely resolve without treatment.
• If your dog has weight changes, lethargy, increased thirst, or thin skin, a hormonal disorder may be the cause. Blood tests are needed to confirm.
• If hair loss appears symmetrical or slow-growing, endocrine disease or chronic irritation may be present. These causes require medical treatment.
• If fleas or flea dirt are present, immediate parasite control is essential. Flea-related hyperpigmentation improves only when fleas are fully eliminated.
• If black spots also appear on the belly, armpits, or groin, systemic skin disease may be developing. Widespread symptoms should not be monitored at home.

Read more: Dog Losing Hair Around Eyes and Mouth (Common triggers)

Key Takeaway

When a dog is losing hair and develops black spots on the skin, the most common causes are hyperpigmentation from irritation, yeast infections, allergies, mites, or hormonal disorders.

While black spots can be harmless signs of chronic inflammation, they often signal an underlying issue that needs attention.

With early care, proper diagnosis, and the right treatment plan, most dogs recover fully and regrow healthy fur while the darkened skin gradually fades.