A dog making to scratch its ear outside.

Why Do Dogs Scratch So Much?

7 mins |

Itchy skin (known as pruritus) is a common and extremely frustrating issue for both dogs and pet parents. We all have the occasional itch, but why do dogs scratch so much? If your pup is constantly scratching or chewing at its body, it is likely due to an underlying issue such as external parasites or allergies.  

Dogs generally scratch because their skin is itchy. While scratching occasionally is a normal canine behavior, excessive scratching is usually due to an underlying medical issue. The main causes of pruritus (itchy skin) in dogs are external parasites (such as fleas or mites) or an underlying allergy. Dogs can be allergic to fleas, something in their diet (food allergy), or something in the environment (atopy). In some cases, pain or anxiety can also contribute. If you have an itchy pup you should see your vet, who will be able to determine the underlying cause and recommend treatment to help them feel more comfortable. 

What Is Pruritus? 

Pruritus is the medical term referring to itchy skin. Itchy dogs may rub, chew, lick, or scratch their bodies. Pruritus is not a specific disease but rather a clinical sign, and several different underlying conditions can cause it. Severity can range from a dog who frequently licks its paws to an animal suffering from severe hair loss, infection, and trauma to the skin, significantly affecting its quality of life. 

Causes of Itchy Skin in Dogs

A dog scratching his ear outside.
Itchy, itchy, itchy!

The most common causes of pruritus in dogs include external parasites, infections, allergies, and other issues such as disease, pain, and anxiety. Let’s start with external parasites. 

External Parasites

External parasites are a common cause of itchy skin in dogs. This may include fleas or mites that live in the skin. Let’s start with fleas. 


Fleas are a nuisance in that they can make your pup itchy, but they can also lead to more severe diseases such as significant skin infections, tapeworms, and anemia (low red blood cell count) from feeding on their canine host. 

Adult fleas feed on a dog. They mate and the female lays eggs, which then fall off onto the ground anywhere your dog spends time (the couch, bed, carpet, etc.). Here the eggs hatch into larvae and then mature into pupae, which can remain dormant in the environment long term. When they emerge as adults they hop onto another host (dog or cat) and the cycle begins again.

Fleas can be diagnosed based on history and a physical exam. You or your vet may see live fleas on your dog or flea dirt (flea poop that will turn red when crushed and mixed with alcohol) when a flea comb is used. 

How To Treat Fleas

To successfully treat fleas there are three important steps:

  1. Treat all pets in the household with flea prevention 
  2. Treat them for at least three months
  3. Treat the environment (remember eggs, larvae, and pupae live in the environment, not on the dog)  

There are many flea treatment products available, and your vet will be able to help you find one that works best for you and your pup. Products come in oral or topical forms, and many also help treat intestinal parasites and prevent heartworm disease as well. It is good practice to make sure any itchy dog is on flea prevention, even if you don’t see evidence of fleas. 


Demodex and Sarcoptes (scabies) are the most common types of mites found in dogs. Scabies is incredibly contagious (it can even be spread to people) and causes extreme pruritus often leading to damaged skin, hair loss, and secondary skin infection. Infected dogs will often scratch excessively if the edges of their ear (ear margin) are rubbed together.

Demodex may be localized or generalized. It is most common in puppies, and, if it occurs in an adult dog, may be an indicator of another underlying disease. Clinical signs may include hair loss, pimple-like or crusty lesions on the skin, and secondary skin infection. 

Mites are generally diagnosed based on a physical exam and skin scraping. Sometimes mites are difficult to find, so your vet may recommend starting treatment even if they don’t see mites on the scraping. Treatment often involves topical medications/shampoos and oral medications. If scabies is diagnosed or suspected, treat all pets in the household. If you are concerned about itchy skin or lesions on your own body, please contact your doctor. 


Just like people, dogs can get infections of the skin. Hot spots or moist dermatitis are common. Depending on the severity of the infection, it may be treated topically with medicated ointment or shampoo or orally with antibiotics and anti-inflammatories. Recurrent skin and ear infections in dogs are often a sign of an underlying issue, likely an external parasite or allergy. Bacteria and/or yeast can cause skin and ear infections. Looking at a sample under the microscope (cytology) can help determine the best course of treatment. 


While allergies in people usually cause red eyes and sneezing, dogs with allergies usually present with itchy skin and recurrent skin and ear infections. There are several things dogs can be allergic to. 

Flea Allergies

While fleas will cause itching in any dog, some dogs actually have an allergic reaction to the bite/saliva of a flea. These animals have an extreme response to even a single flea bite, including itchy skin, hair loss, trauma to the skin, and skin infection. Treatment involves managing any current infections and pruritus, making sure that all pets in the household are on year-round flea prevention, and treating the home environment for fleas. 

Food Allergies

Dogs generally develop allergies to the protein source in their diet. Even if your dog has been eating the same diet for years, it can still develop a food allergy. In addition to itchy skin, they may have gastrointestinal signs, such as vomiting and diarrhea. A dog will need a diet trial to diagnose and treat a food allergy. This involves feeding your dog a novel protein or hypoallergenic diet for three months and watching for signs of improvement. During this time your dog may not eat any other treats or flavored medications. 

Environmental Allergies 

Pollen, dust, and even cats and people can trigger allergies in a sensitive dog. Environmental allergies, known as atopy, may have a seasonal pattern. If you wish to know what your dog is allergic to or treat them with allergy injections, a blood and/or skin test can be performed. Other ways to control symptoms of environmental allergies include wiping paws when coming in from outdoors, and medical management to manage symptoms. There are many excellent medications available that are helpful in controlling signs of allergies and decreasing the frequency of flare-ups, and this is something your veterinarian can help you with. 

Other Causes

Other types of external parasites (lice, walking dandruff) and systemic diseases (liver disease, cancer, endocrine disorders) may also cause changes in your dog’s skin, including pruritus. Pain or anxiety may also lead to excessive chewing or scratching. 

How Veterinarians Diagnose Itchy Skin In Dogs

As discussed above, itchy skin can be a complex issue with multiple underlying factors at play. Your vet may recommend some or all of the following tests to determine the underlying cause and best treatment recommendations for your dog: 

  • History – when/where does your dog (or dogs) scratch? 
  • Physical exam – where on their body is there evidence of hair loss or lesions? Is there evidence of live fleas or flea dirt? 
  • Diagnostic testing – Skin scraping, skin cytology, bloodwork, skin testing, and skin biopsy
  • Diet trial
  • Medication trial 
  • Referral to a dermatologist in complex cases or those not responding to treatment

How Veterinarians Treat Itchy Skin In Dogs

Many dogs with itchy skin have multiple contributing factors, such as an allergy to food and fleas. Treatment aims at reducing their threshold (the point at which clinical signs will occur). While treatment will depend on the underlying cause, possible treatment may include:

  • Flea and external parasite prevention
  • Antibiotics to treat skin infection 
  • Topical medications 
  • Hydrolyzed or novel protein diet 
  • Medications such as Apoquel, Cytopoint, Atopica, antihistamines, and, in some cases, steroids to decrease pruritus 
  • An e-collar or loose t-shirt to help protect your dog’s skin from self-trauma during treatment 

Conclusion: Why Do Dogs Scratch So Much? 

Pruritus in dogs can present in many different ways. You may notice your dog scratching excessively, or maybe they frequently lick at their paws. In most cases, this behavior is due to an underlying medical issue such as external parasites and/or allergies. Your vet will be the best resource to help diagnose and treat your pup’s itchy skin. 

Liza Cahn, DVM
Liza Cahn, DVM
Liza is a veterinarian who graduated from MSU CVM in 2013 and spent five years working in small animal practice. She loved working with dogs and cats and educating owners on all aspects of veterinary medicine, especially animal behavior and dermatology. She has since transitioned to remote work to be able to spend more time at home with her husband, two young kids, and two cats. She is thrilled to be able to combine her passions for veterinary medicine and writing. Liza is located in the Pacific Northwest and enjoys traveling, spending time at the beach, and family movie nights.