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What are Hair Loss Related to Allergies?

Fur loss in a dog is known as alopecia.  It is common for the cause to be an allergy, whether a food allergy, environmental allergy, or parasite allergy all depends on the individual pet.  It can happen anywhere on the body at any stage of your dog’s life.  

If you are able to determine the cause of the allergy, his treatment process will be more successful.  Keep in mind if you do not treat his thinning hair coat, it is likely to worsen and spread to larger regions of his body.

It is normal for your dog to shed some fur, but it is not normal for him to lose large amounts to where his fur is thinning or even bald.  If your dog’s coat is thinning or balding, take him to his veterinarian for an evaluation.


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Symptoms of Hair Loss Related to Allergies in Dogs

Symptoms of this condition may include:

  • Hair loss anywhere on the body (thinning of fur, bald patches) 
  • Constant scratching
  • Constant licking
  • ‘Brown’ feet - also known as saliva stains from licking his feet constantly
  • Crusty skin


Hair loss can happen at any location on the body.  Flea allergies typically start out by causing fur loss on the hind end which slowly works its way up the trunk to the rest of the body.  If it is from a contact allergy, the fur loss will most likely originate where your dog comes into contact with the item.  For example, if he is allergic to the grass, his feet will itch first.  This will cause him to chew at his feet to where he eventually chews off the fur.  If it is a food allergy, the most common starting point of fur loss is also the feet; however, it can occur everywhere else on the body as well.

Causes of Hair Loss Related to Allergies in Dogs

Hair loss in your dog from an allergy can be from one of many things.  One very common cause is flea allergic dermatitis. This is when your dog is allergic to the flea saliva. When the flea bites your dog, it causes intensive itching and therefore scratching.  The scratching and irritation cause the hair to fall out, leading to your dog having a sparse hair coat.

Another common cause includes atopic dermatitis, also known as eczema.  This primarily causes the skin to develop scaly, itchy patches which affect the fur as a result.  Your dog will scratch himself to where he scratches off his fur.  Also, if the skin is unhealthy, it does not produce as healthy of a fur coat as usual.  The cause of atopic dermatitis can vary but it can possibly be from an allergy.

Of course a food or environmental allergy can also cause your dog to lose his fur.  A food allergy can develop slowly over time so that you do not associate your dog’s hair loss with what he is consuming.  It may also develop years after being on the same food so many people do not believe this to be the cause, when in reality it is.  Environmental allergies can also affect your dog when he comes into contact with it or by inhaling it.

Diagnosis of Hair Loss Related to Allergies in Dogs

When you arrive at the veterinarian’s office, she will start her diagnostic process by collecting a verbal history from you.  She will want to know when you first noticed your dog was losing his fur, if and where he has been scratching or licking excessively, and if you have tried to treat it with anything over the counter or not.  As part of her diagnostic process, your veterinarian will need to rule out other possible causes that can produce hair loss with similar symptoms like the one he is presenting with.  She will also want to know if you have fed him anything new lately, if he has had any changes in his routine or home that could cause stress, or anything else information wise that may be helpful to know about his situation.  

Your veterinarian will then continue by performing a full physical exam on your dog.  While it may be obvious where the fur loss is occurring she will want to do a full evaluation of his entire body system.  This will allow her to check for other areas of fur loss or skin abnormalities. During her examination, she will watch for signs of itching or the need to scratch from your dog.  She will check for evidence of parasites, palpate his joint and muscles, and give him an overall evaluation.  

Your veterinarian will come to her diagnosis by ruling out other possible causes of his symptoms.  There are similar conditions that can results in fur loss.  Diagnostic tests the vet may perform include skin scraping, skin cytology, blood work, allergy testing, and a check for other parasites.  The skin scraping will be done to rule out skin mites.  A skin cytology can rule out a bacterial or yeast overgrowth of the skin that can lead to loss of fur.  

During her examination, if there is evidence of fleas or other ectoparasites, she may explain why this may be causing his symptoms. However, dogs with flea allergy dermatitis do not necessarily have to have fleas on him for him to have a reaction.  It takes only one bite from a flea to start your dog’s symptoms.  It is possible a flea jumped on your dog, bit him, jumped off or died, and therefore you do not see fleas on him.  But it is too late; the flea bit him and therefore the flea saliva is causing your dog to have an allergic, overly sensitive response to it.  This is extremely common to see and therefore many owners find it difficult to believe their dog’s symptoms are from fleas. 

For environmental allergies, there is a blood serum test that can test what your dog is allergic to.  Unfortunately, there is no serum, blood, or intradermal test reliable for diagnosing food allergies.  The main way to come to a proper diagnosis is a trial and error dietary study; it is known as an elimination diet trial.  You remove the suspected allergen from your pet’s diet for a minimum of 12 weeks.  This gives his system time to remove any remaining ingredient completely and hopefully his symptoms will begin to resolve.  

Gastrointestinal signs typically resolve between 1 to 3 weeks.  Dermatologic symptoms take much longer to resolve as it takes the skin time to heal.  If his symptoms have resolved during this time, you need to reintroduce the suspected food item to get a confirmation.  If you offer the suspected allergen to your cat again and his symptoms reappear almost immediately, you have your culprit.

Treatment of Hair Loss Related to Allergies in Dogs

Ideally, the best treatment involves treating the region of hair loss, breaking the itch cycle, and removing the underlying cause. If you do not break the lick/scratch cycle, your treatments will be useless.  You must stop the need to lick and scratch in order to break the cycle of fur loss and resulting issues.  You must also address the underlying cause.  Your dog may stop licking for a while, but if there is an underlying cause, it is only a matter of time before he begins again.  

If this condition goes untreated, your dog may develop papules or pustules around the areas of fur loss where he continues to scratch and lick.  This would need antibiotic therapy in order for it to heal.  If this is the case with your dog, the veterinarian will send you home with a prescription of an oral antibiotic.  Medications to be applied topically to the lesion may also be sent home depending on your dog’s needs.  

If ectoparasites are the cause of his symptoms, your veterinarian will suggest a type of flea prevention or other medication to take care of the parasites.  You will also need to make sure you treat your home and yard for fleas to prevent them from bothering your dog.  Be sure to vacuum regularly, wash any bedding your dog uses, and keep anything he regularly comes into contact with clean.

If your dog has a food allergy causing his fur loss, remove it from his diet.  If it is an environmental allergy, there is immunotherapy available in the form of shots or sublingual drops.  Administering these medications will slowly treat your dog’s immune system to not react so severely to the allergen.  Given time, this will allow your dog to not scratch from itching and therefore his fur will grow back.

Recovery of Hair Loss Related to Allergies in Dogs

If you are able to determine the source of your dog’s allergy and remove it, he should recover nicely.  However, if you do not remove the source, your dog will continue to lose fur and probably worsen.  Finding the cause may be tedious, but it will be best for you and your dog in the long run so that treatment is successful.

Hair Loss Related to Allergies Questions and Advice from Veterinary Professionals

8 Years
Critical condition
0 found helpful
Critical condition

Has Symptoms

Itching body smell, hair loss

Medication Used

Ritampin 150 mg

I have an older poodle that was a rescue dog. He is loosing all of his hair, he has a terrible body smell and is always scratching. I have taken him to several doctors and nothing is working. he was given Ritampin 150 mg twice a day. It did not work anymore. I am at a loss. I have asked myself if I should put my dog to sleep because of this problem. I cannot spend anymore money. Embrace Insurance will not pay anymore because they say the ears are related to the body and visa versa...It is very sad.

Unfortunately it is not cheap to find the cause and treat allergies. I had my Scottie. tested for allergies when he was just a couple months old and he has been on Apoquel (environmental allergies) since then. It worked great until a year ago when he had a pH problem and since then the Apoquel doesn't seem to help much. Allergen shots, pills, products to try and help the itch- I don't even want to think how much I've spent in 6yrs. It is very frustrating but I signed up to take care of him and my 3 yr old female Scottie so I keep trying to make his life more comfortable. Having a Care Credit card has helped considerably since you can spread payment over time.

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9 Years
Serious condition
0 found helpful
Serious condition

Has Symptoms

Hair Loss
Dry skin

I have a 9 year old doxie mix. He’s always gone one and off with his nonstop scratching. Usually we take him to the vet, the give him a shot and he goes back to normal. Now it’s worse than ever, he’s nonstop scratching. He’s loosing hair everywhere and his skin smells bad. It makes me cry to see him like this :(. we went to the vet a few weeks ago to get the shot, but we have yet to see improvement. Maybe it’s food allergies? I don’t know, all i want is my happy dog back :(

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9 Years
Moderate condition
0 found helpful
Moderate condition

Has Symptoms

Hair Loss

My 9 yr old boxer is losing his hair in patches. He does not scratch; it just going away. I feed him a low-caloric diet with not grains and no GMO. What can it be.

Dr. Michele King, DVM
Dr. Michele King, DVM
1611 Recommendations
Possible causes for hair loss in dogs can be bacterial, fungal or parasitic infection, allergies, seasonal issues, or endocrine diseases. Since i cannot see him, it would be best to have him examined by a veterinarian to try and determine what might be going on. Your veterinarian will be able to see him, give you any recommendations on what might be happening, and any recommendations on possible treatments.

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