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My Dog Is Constantly Scratching & Biting Himself: Here Are 9 Reasons Why 

Constant scratching and biting represent a problem and is most often caused by skin infections, external parasites, stress, anxiety, boredom, allergies, internal diseases, or insect bites. Besides scratching and biting, dogs can also have hot spots, dry skin, hair loss, and other symptoms. Contact the vet if your dog exhibits this behavior.

Dogs can drive their owners crazy. Some of the things that often do so are scratching and biting. But dogs aren’t in control of this behavior if they’re experiencing an external issue.

Our pets often scratch and bite themselves if they have a skin issue.

Common causes behind skin issues are pollen, dust, knots in the fur, or dead cells that matte their coat. If they stay in the fur long enough, these elements can irritate pets’ skin, causing itchiness.

Sometimes dogs can scratch for more severe reasons such as certain internal diseases, massive flea infestations, or stress and anxiety.

Always contact your veterinarian for a correct diagnosis and proper treatment.

In this article, you will learn why dogs scratch and bite constantly, what you can do, and more.

Why Is My Dog Constantly Scratching and Biting?

Dogs constantly scratch and bite for many reasons. The most common are fleas, mosquitoes, boredom, food allergies, and others. Dogs also adopt this behavior when they are stressed or anxious. Inspect your dog’s skin, and if there are no external irritants, your pet is probably suffering from boredom or anxiety.

Occasional scratching and biting are normal for dogs. But, it becomes a problem when dogs do it so constantly that they end up self-mutilating. 

The most common reasons why dogs constantly scratch and bite include as follows:

  1. External parasites
  2. Environmental factors
  3. Food
  4. Internal diseases
  5. Insect bites
  6. Skin infections
  7. Boredom
  8. Stress
  9. Anxiety

Common symptoms of these conditions include:

  • Constantly scratching and biting
  • Hair loss in places where dogs scratch
  • Hot spots
  • Secondary infections
  • Wounds and bleeding
  • Yelping

Other symptoms may also occur, depending on the cause.

1. External Parasites

External Parasites on dogs

Many parasites specific to dogs (such as fleas, mites, or ticks) can make dogs itch. They can also transmit severe diseases, which is why they need to be removed as soon as possible.


Flea infestations are common causes of itching in dogs. Fleas infest dogs from other infested animals, or they jump on your pet from the environment (grass, the car, etc.).

Itching caused by flea infestation occurs mainly on the back, tail, abdomen, inner thighs, and neck.

Some dogs are more sensitive to flea saliva and develop flea allergy dermatitis, causing the following symptoms:

  • Itchy lesions and long-term scratching
  • Skin tags and hot spots (lower back, the tip of the tail, and caudal and inner thighs)
  • Red and inflamed skin
  • Hairless areas, especially on the lumbosacral area, ventral part of the abdomen, and base of the tail

In addition to flea allergy dermatitis, fleas present a risk for other medical issues:

  • Anemia
  • Tapeworms
  • Cat scratch disease
  • Typhus
  • Plague
  • Tungiasis

To get rid of fleas, you have to use antiparasitic treatments regularly.


There are many mites that parasitize dogs. Some are harmless while others cause itching and serious illnesses:

  • Cheyletiella spp. (predatory mites)
  • Sarcoptes scabiei (Sarcoptic mange)
  • Trombicula autumnalis (harvest mites)
  • Otodectes cynotis (ear mites)

Contact your veterinarian if your dog is constantly scratching and biting and has specific symptoms of mite infestation. The treatment for mites consists of baths with specific products prescribed by the veterinarian.

Cheyletiella spp. (predatory mites)

These mites are found in dogs, cats, and rabbits. Cheyletiella mites are transmitted through direct contact or from the environment. They live superficially on the skin and feed on surface debris and tissue fluids.[1]

The itching this mite causes varies in severity. It can be located on the back, shoulders, and sometimes the outer part of dogs’ ears. Dandruff will also appear on dogs’ backs.

Sarcoptes scabiei (Sarcoptic mange)

Sarcoptes mites are host-specific and highly contagious. They are transmitted both to other animals and humans through direct contact with the affected dogs/persons or from the environment.

Sarcoptes dig tunnels into the keratin layer of the skin, where they lay eggs and defecate. They feed on dead skin cells and tissue fluid.

Dogs scratch and bite due to the itching caused by mites, but also due to the allergic reaction to their metabolic products.

The itching occurs mainly on the earlobes, joints, abdomen, and chest. Over time, it spreads to the entire body.

Affected dogs have red and inflamed skin, hair loss, and bleeding or crusty lesions.[2]

Trombicula autumnalis (harvest mites)

The harvest mite is an orange-red parasite about the size of a pinhead that occurs mostly in summer and fall. They have bright colors, making them easy to spot on some dogs.

Only larvae live on animals and feed on lymph and disintegrated skin cells.[3] They attach to the skin of animals in a similar way to ticks.[4]

The larvae are found in tall grass where they wait for their host. They attach primarily to the paws (between the toes), belly (especially on the nipples), and head.

The bite of larvae can cause allergic reactions with severe itching. Even after the parasites are removed, the itching can persist for a while.

Otodectes cynotis (ear mites)

Ear mites affect the external ear canal and rarely the skin around the ear where they feed on ear wax and skin oils.[5]

They are transmitted through direct contact with infected animals. The most affected are puppies and rarely adult dogs.

Ear mites cause many symptoms:

  • Strong itching in and around the ears
  • Constant scratching
  • Head shaking
  • Abundant, foul-smelling gray-black ear secretions
  • Yelping

2. Environmental Factors

Skin Infections That Cause Black Spots and Hair Loss

Environmental factors can cause allergies. Some dogs are more sensitive to dust, mites, pollen, mold, or other environmental substances and can develop a series of symptoms, including itching.

Whether it is a contact allergy or an allergy to environmental factors, they manifest through the following symptoms:

  • Itching on the face, paws, extremities, abdomen, and inner thighs
  • Hot spots
  • Hair loss
  • Secondary skin infections

3. Food

dog with Nausea eating grass

Food also causes allergies, even if your dog has been eating the same food for a long time. It is one of the most common allergies in dogs.

Dogs can be allergic to many ingredients. This is most often an animal protein, such as beef, chicken, pork, eggs, fish, and rabbit.[6]

Dogs with food allergies show the following symptoms:

  • Constant scratching and biting all over the body
  • Dry skin and crusts
  • Vomiting
  • Diarrhea
  • Hair loss
  • Hot spots
  • Secondary skin infections
  • Bad odor due to secondary skin infections

4. Internal Diseases

Cushing’s Disease
Image Source

Certain internal diseases cause dogs to scratch and bite constantly:

  • Kidney and liver diseases (sometimes)
  • Hypothyroidism
  • Cushing’s disease
  • Some autoimmune diseases

Kidney Disease

Kidney diseases cause itching due to calcium and phosphorus deposits in the skin.[7]

Other symptoms include:

  • Bad breath
  • Matted fur
  • Weight loss
  • Lack of appetite
  • Apathy
  • Anemia and others

Liver Disease

Sometimes liver diseases can cause dogs to scratch and bite their skin. Other symptoms include:

  • Loss of appetite
  • Weight loss
  • Vomiting and diarrhea
  • Feces with blood (sometimes)
  • Jaundice
  • Confusion
  • Seizures etc.

Related Article: Why Is My Puppy Itching? 5 Reasons Why It Happens

5. Insect Bites

Puppy Itching due to Insect bites

Insect bites can cause local reactions that then cause intense itching and red bumps. Local allergic reactions are caused by insect saliva that contains irritating substances. 

Dogs with insect bites may show the following symptoms:

  • Red bumps and hot spots
  • Intense itching and scratching

In rare cases, secondary skin infections and hair loss also occur.

Insect bites usually go away in a few days without treatment. If they persist, you can try antihistamine and/or antibiotic ointments (in case of secondary infections).

6. Skin Infections

Dog Food Allergies

Bacterial and fungal infections are the most common skin infections that cause itching. They appear when the natural defense system of the skin is overcome, allowing the overgrowth of bacteria on the skin (e.g. staphylococci). 

Other microorganisms, such as yeasts and fungi, can also take advantage of skin changes and multiply excessively. 

Dogs with skin infections may show the following symptoms:

  • Intense itching
  • Constant scratching and biting until they self-mutilate
  • Yelping
  • Hot spots
  • Hairless areas
  • Moist skin
  • Wounds
  • Crusts
  • The fur of white dogs can acquire a reddish color
  • Musty or rancid smell

To prevent skin infections, groom and brush your dog regularly and clean its skin folds, ears, and between the toes.

Take your dog to the vet if it experiences symptoms.

7. Stress and Anxiety

Dog Panting and Drooling

Stressed and anxious dogs scratch more often. Dogs can become stressed or anxious for countless reasons, some more harmless than others.

Stress and anxiety in dogs can manifest as follows:[7]

  • Scratching and biting
  • Vocalizations
  • Urination and defecation in unauthorized places
  • Panting
  • Shedding
  • Drooling
  • Shaking and others.

It is important to pay attention to your dog and determine what causes your pet stress and reduce those stressors as much as possible.

Besides, there are veterinary treatments for anxious dogs that can help them have a comfortable life.

How to Stop Your Dog From Scratching and Biting Himself

To stop your dog from scratching, you can:

  • Give your pet toys or bones to chew.
  • Play with your pet to distract it.
  • Put on a special collar.
  • Take your pet to the vet to treat the medical problem that led to scratching in the first place (if any).
  • Change its food if your pet has a food allergy.
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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