Saturday, March 26, 2011

Why Is My Dog So Itchy? Top 5 Causes Of Itching In Dogs

by Lorie Huston, DVM  

Dogs can become itchy and begin to scratch for many different reasons. However, allergies of various types are among the most common causes.


Canine Flea Allergy Dermatitis

An allergy to fleas is one of the most common reasons dogs become itchy. When a flea bites a dog, it injects a substance into the dog’s skin which causes the allergic response.

For a sensitive dog, one flea bite can make the dog extremely itchy. 

One of the most difficult things to understand is that often no overt evidence of fleas is present even though a flea allergy is the reason for the dog’s discomfort. This inability to find evidence of fleas stems from the fact that only one flea need be present and bite the dog in order for the allergic reaction to occur.

In addition, dogs frequently groom themselves and remove the evidence of the fleas through their grooming behavior. Therefore, not being able to find fleas does not rule out a flea allergy as a cause of itching in a dog.

Canine Atopy

Canine atopy is a type of allergy that causes a hypersensitivity reaction to environmental stimuli, such as dust mites or pollens. It is a common disorder in dogs and typically causes scratching and itching. Finding the source of the allergy in these cases can be challenging.

Food Allergies in Dogs

Food allergies are another common cause of itching in the dog. Food allergies can result from reactions to any ingredient within the food but beef, chicken and wheat are some of the most common culprits.

Bacterial Skin Infections in Dogs

Bacterial infections in the skin, commonly called bacterial dermatitis, are another common cause of itchiness in dogs. Bacterial skin infections frequently occur as complications to canine allergic skin disease and are usually a secondary disease.

Bacterial dermatitis must be successfully treated with antibiotics in order to evaluate and control the underlying allergic skin condition.

Canine Yeast (Malassezia) Skin Infections

Yeast skin infections most commonly involve a specific type of yeast known as Malassezia. Like bacterial skin infections, yeast infections are generally secondary to another underlying disease, often allergic in origin. Antifungal medications, such as ketoconazole, are needed to treat canine yeast infections.

Most Common Causes of Itching in Dogs

The three most common causes of itching in dogs are flea dermatitis, atopy and food allergies.

Any of these three types of allergies can be complicated with secondary bacterial or yeast invaders resulting in bacterial and/or yeast skin infections in affected dogs. These skin infections can become quite itchy in their own right and cause extreme discomfort and distress for the infected dog.

Less commonly, other causes, such as canine ringworm (dermatophytosis) or sarcoptic mange may cause itchiness and discomfort as well.


Lorie Huston has been practicing veterinary medicine for over 20 years. Besides a successful career in a busy small animal hospital in Providence, RI, Lorie is also a successful freelance writer specializing in pet care and pet health topics. 

Currently, she is the feature writer for the Pet Care section at and the National Pet Health Examiner at Lorie also publishes her own blog, The Pet Health Care Gazette and manages an increasingly popular facebook page, The Voice of Pet Care

Articles by Dr. Huston:
Lyme Is Lame (Pun Intended)
The Ticking Bomb
Don't Let Heartworm Become A Heartbreak!
Summer Perils: Blue-green Algae
Your Dog And Leptospirosis
Canine Parvovirus
Canine Distemper Virus


  1. How do you suggest a pet owner most effectively find out what the dog is actually allergic to? Such as, to find out if he is allergic to environmental/seasonal things, fleas, or food. Do dogs have scratch tests like people do? I know the usual way I see recommended to find out with food is to do an elimination diet, but unless run very slowly, like 3+ months on one protein, they can become based on assumptions. If dogs do have something analogous to a scratch test, is it expensive?

  2. For food allergies there are two options
    1) elimination diet
    2) spot allergy blood test

    There are proponents of each method, or they work in combination.

    The spot allergy test also pin points environmental allergies. Jasmine had it done and lists everything from food, pollens and other environmental allergens.

    There might be more substances show up on the test than the dog is actually truly allergic to, but it gives a good baseline.

    This is where we had Jasmine's done
    Spectrum spot allergy test

    3) Yes, there is also a type of skin test, similar to human scratch tests, except it is intradermal (the substance is injected into the skin)

    Allergy Testing & Immunotherapy in Dogs

  3. The spot allergy test was around $100 or something, can't remember, it's been a long time. I'm quite sure it wouldn't be over $150 or so.

  4. I have learned the hard way to keep my house and yard flea free no matter what after one of my dogs developed a flea allergy and kept us all awake scratching for days. But then he may have enjoyed the attention. :-)

  5. :-) What do you do/use to keep your house and yard flea free?

  6. Thanks for the info! We've had allergy issues with Bella in the past, and I'm always on the lookout for a flare up.

  7. What do you think about the home remedy of adding a tablespoon of cider vinegar to doggy's water dish as a means to repel fleas?

  8. Well, apple cider vinegar is highly regarded by many holistic vets and experts for many reasons.

    I am not really convinced how effective it might be for flea prevention. Generally I don't think there is any harm in trying, but I'd watch the amount of the vinegar, because too much acidity can do damage.

  9. When we decided to get an animal shelter puppy we knew it had to be a mutt. The chances of them having health problems, from over breading is much lower. Well to our surprise and a 150 pound heaver dog (rottweiler/ husky mix) we found out he indeed had food allergies. Beef, chicken, wheat, eggs and soy. With so many allergies it was a chore finding a food that he could eat and we could afford! You just never know but when you love them so you do what needs to be done.

  10. It is believed that mutts are generally healthier. But that's not always true. When you're mixing DNA, you really never know which traits from which breed you'll end up with.

    Sadly, food allergies are far too common. Jasmine is also allergic to eggs, chicken and soy. Fortunately not to beef. I can see how it would be difficult finding a food that would agree with your pup. But you're right, if you love your dog, you'll do what it takes.

  11. My dog is allergic to beef, fish and chicken! She has been doing pretty well on Lamb & Rice . .but as soon as spring hits, the itching begins :) We do our best to keep her comfortable and we have tried EVERYTHING!!

    I linked to your article from Please feel free to post any of your articles there!

  12. Hi Julie.

    Thank you for linking to my article! :-)

    Wow, fish too? Chicken and beef are common, being allergic is actually quite rare. Lamb and rice is a good choice if the dog never had it in the past. Sadly, new allergies can develop over time, so it could happen that eventually your dog will develop allergy to lamb and/or rice as well.

    The other choice apparently is the hydrolyzed food, where the protein is broken down into smaller particles (amino acids).

    Sadly, dogs quite commonly have combination of both food and environmental allergies (these are typically seasonal) to pollens, but also to dust and other things.

    These are much harder to treat. If there aren't too many substances your dog is allergic to, you could consider spot allergy blood testing followed up by allergy 'vaccination'. This can be quite successful unless there are too many things your dog is allergic to. The more allergens, the less successful the treatment attempt would be.

    Some holistic vets believe that if the dog detoxifies it will do away with the allergies. I have a friend who's trying just that, so far there is some good progress.

    Seeing a holistic vet wouldn't probably hurt anything in either case.

    I also have a couple friends who's dogs got rid of their allergy symptoms when put on raw diet. Any of these strategies should be done after consultation with your or a holistic vet.

    There are also some other techniques, such as NAET. I would try that myself, but it is not available where we live.