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Dog Losing Hair in Patches? Here’s Why

Finding a bald patch on your canine companion can be alarming, let alone several bald patches. 

Shedding is a normal part of life with a dog, but sudden, unusual hair loss is not. Patchy hair loss can be a symptom of several conditions, so it’s important to correctly identify the underlying cause before you start exploring treatments. 

Here’s what you need to know about the most common causes of canine bald spots.

bald spots on poodle mixParasitic Infections

When we think of parasites, we often think about intestinal worms, but parasites can also infest pets’ skin. 

These creatures survive by spreading from host to host, so parasite-related hair loss in your dog can often be a sign that the other pets and humans in your household have been exposed. 

Even the best-groomed dogs can pick up parasites from dog park encounters, so high-tail it to your vet if you notice hair loss that is accompanied by irritation, lesions, or thickened skin.

Mange Mites

Mange is a condition caused by parasitic mites that burrow and lay eggs in the skin. There are two types of mange: demodectic and sarcoptic. Demodex mange primarily affects immunocompromised dogs and doesn’t readily spread to other species. The mites that cause sarcoptic mange, however, can infest humans in the form of scabies.  

Mange is characterized by painful symptoms:

  • Extreme itchiness
  • Red, irritated skin
  • Yellow crusts
  • Bacterial infections
  • Thick, darkened skin
  • Swollen lymph nodes

Mild mange can worsen quickly, so don’t lose time seeking treatment. 


Contagious and itchy, ringworm is marked by distinctively circular bald patches with raised lesions. Despite its name, ringworm isn’t caused by worms at all — it’s fungal. 

The fungus that causes ringworm passes easily when dogs have skin contact with infected animals or use contaminated brushes, bowls, or bedding. Though it’s treatable, this uncomfortable skin condition can affect both pets and humans, especially small children and people with depressed immune systems.


Fleas are one of the most common canine allergens. Whether your dog is truly allergic to flea bites or merely sensitive, a flea infestation can trigger obsessive scratching, licking, and chewing that is highly irritating to skin.

If red, hairless patches emerge in areas that your dog can reach with their mouth or hind leg, flea-related dermatitis could be to blame. Get your pet treatment that will soothe their skin right away, because continued scratching and chewing can lead to serious skin infections.

Allergic Dermatitis

Corgi with itchy skin and patchy hair loss

Surprisingly, food allergies and sensitivities are more likely to impact your dog’s skin than their stomach. 

Allergies can develop at any point, meaning that a protein source your dog has enjoyed their whole life may suddenly cause itchy skin, hives, or hair loss. If you suspect that your pet has developed a food allergy, ask your vet about planning an elimination diet to pinpoint the root cause. 

Cushing’s Disease and Hair Loss

As dogs age, changes to their endocrine system can affect the health of their coats. 

Cushing’s disease, or an overproduction of the hormone cortisol, is most often caused by a benign tumor pressing on the adrenal or pituitary gland. Cushing’s disease is most common in dogs over age six, and is usually characterized by:

  • Hair loss
  • Thin skin
  • Pot-bellied appearance
  • Increased thirst and appetite
  • Lethargy

Depending on the size and location of the tumor, Cushing’s disease can be addressed by surgery or managed through medication. 

Yeast Infections

Dogs with long, floppy ears or skin folds require special attention at the groomers. Moisture and oils can collect in crevices or between dogs’ toes, leading to an overgrowth of yeast. 

The first sign of yeast dermatitis is usually an unpleasant, musty smell, but if left unchecked, the irritation will lead to hair loss. Your vet can prescribe antifungal medications and ointments to keep yeast in check.

Stress-Related Bald Patches in Dogs

If you’ve ruled out medical explanations for hair loss, it’s possible that the explanation may be behavioral. 

Just like humans can respond to stress by biting our nails or picking at our skin, boredom and anxiety can cause dogs to chew or bite their fur to the point of hair loss. 

Ensure that your dog is getting plenty of attention, exercise, and stimulation. Ease separation anxiety by providing your pet with interactive toys and treats to keep them engaged in your absence. If issues persist, talk to your vet about options for managing your dog’s anxiety through medication.