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Crusty Scabs on a Dog’s Back: Causes, Treatment, Prevention

Skin issues are very common with dogs, and often easily treatable. We run down the major causes of crusty scabs on dogs.

Crusty scabs on a dog’s back are fairly common and usually not a serious medical issue.  The scabs (atopic dermatitis) are typically caused by different types of skin conditions or external parasites. These skin conditions and the volume of parasites can both worsen depending on the environment the dog is in, the food they’re eating, and the shampoo being used on their coat. 

If you are not certain what is causing your dog’s scabs, getting a veterinarian’s examination is the best course of action to avoid any misdiagnosed conditions and ensure the dog’s health and comfortability.

Causes of Crusty Scabs on a Dog’s Back

The primary causes of crusty scabs on a dog’s back are allergies, external parasites, fungal infection, bacterial infection, yeast infection, immune disorder, nutritional deficiency, and hormonal imbalance.


Allergies that result in skin issues come in the form of environmental allergies, food allergies, and sensitivity to pollen.

Food Allergies

Although food allergies are a lot less common in dogs than humans, they are still prevalent. Many dog foods limit chicken, for example, because it’s known to cause skin reactions. 

Some dog food brands have started mimicking human food health trends and have begun making limited ingredient, grain-free food. Grains can be a trigger for the flare-up of a skin issue in some dogs. The idea of the limited ingredient diet is that the fewer ingredients there are, the less likely it is to cause any kind of allergic skin reaction. 

The skin reaction resulting from a food allergen is usually mild to severe itching, with scabs resulting from excessive scratching.

Environmental Allergies

It’s easy to think of environmental allergies as just being related to pollen. However, environmental allergies that cause skin irritation in dogs can be anything ranging from shampoos to lawn treatments, floor cleaner, and even laundry detergent. 

For example, washing a dog bed with a new laundry detergent can cause skin irritation. This is something to keep in mind when switching any cleaning products used on or around dogs. Just like human skin can get irritated by different products, so can a dog’s skin.

Sensitivity to Pollen

Dogs commonly have a sensitivity to pollen, and it can cause dermatitis. This results in itchiness, rashes, blisters, sores, and scabs. These effects occur once the pollen has had direct contact with the dog’s skin, making pollen-induced dermatitis a lot more common in dogs with shorter fur.

External Parasites

External parasites majorly irritate a dog’s skin and cause them to lick, chew, and scratch their skin excessively. This ends up causing severe soreness, tenderness, and of course, crusty scabs. These external parasites include fleas, ticks, and mites.


Fleas are the most common external parasites that dogs have to face. These tiny parasites might not even be visible at times, which can cause a significant problem. Their ability to hide in carpets, bedding, and backyards (all the places dogs are likely to frolic) increases the chances of excessive flea bites.


Ticks feed on the blood of dogs resulting in severe skin irritation. The upside about ticks is that dog owners are usually able to see ticks easily. Getting tweezers to remove the tick is a good idea, but the tick must be pulled gently.

Sometimes a remainder of the tick can get stuck in the dog. Instead of trying to pry it out, it’s recommended to just let the dog’s body naturally expel it and apply antibiotic ointment.


The two types of mites that eventually cause crusty scabs on a dog’s back are scabies mites and Demodex mites. Both kinds of mites result in mange. This condition is severe and can cause dogs to lose all their fur and be covered in crusty scabs.

The difference between the two types is that mange caused by scabies mites is contagious to humans and other animals white demodectic mange is not. Scabies can also be more severe and cause more damage.

Fungal Infection

Just like humans can get ringworm, so can dogs. Puppies are very vulnerable to this highly contagious fungal infection due to their immune systems not being built up yet.

Ringworm is caused by fungus that results in skin irritation, hair loss, itchiness, and scaly skin. Ringworm is easily identified because of its ring-like patches of irritation that it leaves behind on a dog’s skin.

Bacterial Infection

Bacterial infections typically co-exist with another type of skin disorder. These infections happen when a dog is constantly chewing and licking their inflamed skin. As they’re doing this, their skin begins to break open and becomes susceptible to bacteria entering, causing a secondary infection.

As bacteria enter, sores resembling acne can start to develop and cause even more irritation, which causes even more scratching, which inevitably leads to more crusty scabs. 

Yeast Infection

Yeast infections are one of the most common types of skin infections a dog will face in its lifetime. Yeast builds up in areas of the body that are warm and moist. When there is an outbreak, this can cause irritated and extremely itchy skin. Dogs try to relieve the itching by chewing and scratching incessantly, which results in crusty scabs.

Yeast infections in dogs are relatively easy to spot. Besides the scabs, the affected skin is normally discolored and typically darker than the rest of the skin.


Impetigo is a bacterial infection that is most common in puppies.  It causes blisters that can break, with pus forming scabs.  They usually occur on the smooth area of a puppy’s belly, and is easily treated with a topical ointment prescribed by your veterinarian.

Hormonal Imbalance

Hormonal imbalances can cause dogs to lose their hair. This, in turn, results in skin sensitivity and irritation and causes all those crusty scabs. Sometimes skin irritation caused by hormone imbalances can be the precursor to certain diseases like hypothyroidism, Cushing’s Disease, and even some forms of tumors.  This is one of the serious underlying issues that can be the cause of crusty scabs.

Immune Disorders

Just as in humans, auto-immune disorders can wreak havoc on their skin. Because these disorders suppress a dog’s immune system, their skin cannot fight off irritants like it usually would be. This leaves them open to all types of skin conditions that can lead to scabs and sores. 

Nutritional Deficiency

It can be easy to forget that a dog’s skin needs moisture too. Instead of putting on lotion and creams, however, dogs get their moisture from their diet. Dry skin can result in itchiness and rashes, causing incessant scratching and scabs.

Dry skin also makes dogs more susceptible to parasites. And since parasites are likely to attack unhealthy dogs, they become a major target if they aren’t eating enough vital nutrients.

Hot Spots

The commonly used term “hot spot” refers to acute moist dermatitis or pyotraumatic dermatitis.  It is a skin infection that occurs when normal skin bacteria overtake skin which has been damaged by a dog’s licking, chewing, or scratching.

Any of the above conditions can cause a dog to lick or chew excessively, starting this vicious cycle. The irritated area becomes moist, red, and ultimately infected.  When pus oozes from the affected skin, it dries and creates the crusty scabs that you see.  It is part of the healing stage.  It is very uncomfortable for the dog, and they may be sensitive to the touch.

If dogs could just leave the itching areas alone, hot spots wouldn’t develop.  And if they could leave the hot spots alone, they would heal much more quickly.  But they irritation and itchiness demands their attention, which is why hot spots can remain for a long time.

The Examination Process

Of course, it’s always best to check with a veterinarian when trying to diagnose the causes of scabs because one misdiagnosed skin condition can easily worsen and possibly even be fatal. Here are the different types of examinations a veterinarian will perform:

  • Cytology: Veterinarians will collect a sample of the skin lesion with a piece of tape. They’ll then examine it under a microscope and look for bacteria and yeast. This is usually done if the vet suspects there may be an underlying condition or secondary infection.
  • Skin Biopsy: Dogs are put given a sedative and local anesthetic. After this, the vet will remove a small piece of the skin lesion and send it over to a pathologist. This is typically done if the vet sees the lesions as unusual or if all the other testing fails.
  • Allergy Testing: If the vet suspects an allergen is involved in the skin irritation, they will test this by injecting allergens into the skin and identifying which ones cause a reaction. Surprisingly, skin allergy testing is a lot more accurate than blood testing. However, a vet may choose to do both just to ensure accuracy.
  • Cultures: Sometimes, dogs can have bacterial infections that don’t respond to antibiotics. In this case, a bacterial culture is administered to determine which bacteria are resistant and which antibiotics can get rid of it. 

Fungal cultures are examined for about ten days. Samples of skin are placed on a media and are closely watched to see if any more fungus grows and what type of fungus grows. From here, the vet can determine the next course of action.

  • Skin Scraping: Skin scraping helps find Demodex mites but is a little harder in finding scabies mites. Skin scraping can also be used to find other external parasites like fleas and ticks.


After determining the correct cause of the crusty scabs by a veterinarian, the treatment plan will follow. If the skin irritation is caused by diet (deficiencies or type of food), a change in the type of food needs to occur.

If the lesions and redness of a dog’s skin are caused by the external environment (cleaning products and parasites), the owner needs to reassess the situation. Switching to non-scented laundry detergent and shampoos can greatly help a sensitive dog’s skin. Keeping up with a flea and tick prevention regime can help keep the dog free of harmful parasites.

Bacterial and fungal infections can both be treated with different medications. And if the cause of skin irritation happens to be because of immune disorder, hormone imbalance, or other health-related condition, that condition will need to be addressed first.

Often, the use of an elizabethan collar is recommended to keep the dog from causing further damage to the affected area.  


Obviously, how you prevent scabs from developing or returning depends on the root cause of them.  But a few basic, time tested approaches can keep a good percentage of cases from occurring.


There is a direct correlation between a dog’s diet and the health of their skin and coat.  Feeding a quality, well balanced diet with proper nutrients can go a long ways toward healthy skin.  Certain grains are known to create skin and allergy issues.  Trying a grain free or limited diet is often a good place to start if food allergies are suspected.

Fish Oil Supplement

There are a number of benefits of fish oil supplements, and healthier skin is one of them.  Check with your vet to see if they recommend a simple daily fish oil supplement. 


If your vet has determined that environmental allergies are the culprit, Benadryl or Zyrtec are over the counter medicines that can help alleviate symptoms like itchiness and rashes. Check with your vet for proper dosage; the standard dose is 1-2 mg per pound of your dog’s body weight.  WARNING: Only use regular Benadryl, and NOT Benadryl-D, which has a decongestant which is toxic to dogs.

Anti-bacterial and Anti-Fungal Shampoos

If the source of your dog’s itching and resulting scabs is a bacterial or fungal infection, regular use of an anti-fungal shampoo can help to keep infection in check.

Flea and Tick Meds

Maintaining a standard flea and tick treatment regimen is a good idea if they pose a potential problem.  Your dog will thank you.

General Hygiene for Your Dog and Home

Keeping your dog and your home clean and parasite-free can be a big step towards preventing skin issues. It usually doesn’t take much effort, and the reward of a healthy dog is worth it. Not to mention, hygiene is always a good thing!


Bathe your dog regularly.  Depending on your dog’s coat and activity habits, you should bathe your dog at least once a month, and more frequently if necessary.  


Brushing or combing your dog daily helps keep your dog’s skin clean and its coat healthy. Not only does it clear the coat of loose dirt and other foreign matter, but it also stimulates the release of natural oils which are then spread across the skin as a protective defense against bacteria and fungi.  Also, most every dog loves to be brushed, so you won’t get any arguments from them.

Pick Up Poop

This shouldn’t have to be said, but picking up and disposing of dog poop in a timely manner is essential for many reasons. You don’t want your dog playing or running through their own poop or that of other dogs. It can be a potential source of skin issues.

Launder Your Dog’s Bedding

It’s a good idea to wash your dog’s bedding (all of them if they have more than one) at least weekly.  If they sleep with you in your bed, do the same for your bedding. Make sure your dog is not sensitive to your laundry detergent, as that can create allergic reactions on the skin.

Sweep, Mop, and Vacuum Floors

If you have pets, you can’t clean your floors too often.  All sorts of microscopic nastiness can lurk inside your carpets or rugs, or on your wood or tile floors.  Better that it’s in your vacuum or dust pan and not in your dog’s fur.


Crusty scabs on a dog’s back can have many causes due to internal and external issues. With proper diagnoses from a veterinarian, dogs can usually return to normal or are at least be put on medications to help calm the severity of skin issues.

Superb Dog Editor

Superb Dog Editor

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