Pet food discussions seem uniquely capable of getting readers of this blog excited. Let’s shake things up.

Recently a reader brought up a question in the discussion of corn as a pet food ingredient. The reader was curious about the allergenic effects of corn. Is corn likely to cause allergic reactions in dogs and cats?

Cats and dogs with food allergies most commonly suffer from skin and ear problems. Gastrointestinal upset also is possible.

Numerous studies have been performed to assess the most highly allergenic food ingredients. A paper published in the September, 2002 issue of Advances in Small Animal Medicine and Surgery attempted to tabulate the results of 22 different studies into a cohesive set of data. This “study of studies” has the advantage of large sample sizes that are likely to be statistically significant. It has the disadvantage of being authored by Philip Roudebush of the Hill’s Science and Technology Center. Although I can’t see any evidence of data twisting in the paper, readers should be aware that the data were tabulated by a person employed by a pet food manufacturer. Consume as many grains of salt as you desire while reading the results.

The leading food allergens in dogs as determined by the study of studies are listed below. Numbers in parentheses indicate percent of food allergy cases caused by each ingredient. They do not indicate the likelihood that a pet will suffer an allergic reaction after consuming the ingredient.

Beef (34%)

Dairy (20%)

Chicken (20%)

Wheat (16%)

Egg (7%)

Lamb (5%)

Soy (5%)

Corn (3%)

Pork (2%)

Rice (2%)

Fish (1%)

In cats, the following allergens were found to be most problematic.

Beef (29%)

Dairy (29%)

Fish (23%)

Lamb (7%)

Chicken (7%)

Wheat (5%)

Corn (5%)

Egg (4%)

A different study of studies was published in April, 2006 in the online journal Critical Reviews in food Science and Nutrition. The authors were Belgian, and in a quick review of the matter I could not find evidence of links to pet food companies. Here are their conclusions.

The leading allergens in dogs as determined by the authors are beef (36%), dairy (28%), wheat (15%), egg (10%), “diverse” (includes corn, rice, “biscuit”, chocolate [They're feeding chocolate to dogs in Belgium?! Don't they know it's potentially toxic? And isn't Belgian chocolate too good to give to dogs?], and gluten) (10%), chicken (9.6%), “canned foods” (8.6%), soy (6%), “dry foods” (6%), pork (4%), rabbit (1%) and fish (1%).

The authors concluded that the leading allergens in cats are “commercial foods” (ingredient causing allergies undetermined) (25%), beef (20%), dairy (15%), fish (13%) “diverse” (includes penicillin, “brand’s essence”, gluten, and viscera) (11%), lamb (7%), poultry (5%), barley and wheat (5%), additives (2%), rabbit (1%) and egg (1%).

Percentages in both studies may not add to 100 due to rounding.

Readers are invited to post links to additional studies in the comments section.

Photo: may cause allergic reactions in dogs. That leaves more for me!

See related Vet Blog entries:

• How Much and How Often Should I Feed my Dog?
• What Makes Hypoallergenic Diets Special?
• Does Pet Food Cause Health Problems?
• Do Puppies Need to Eat Puppy Food?
• Enjoy Treats in Moderation

My dog is in great distress either from fleas or allergies or both or something else. She is constantly biting at herself. What should I do ASAP?

Background: I rescued this female two-year-old Jindo from a shelter 3 days ago. It appears as tho she had recently given birth. She was spayed at the shelter before she was released. I was told I have to wait 10 days before having her bathed. I gave her Frontline. The itching and biting herself has not subsided. I was told at Petco that the Frontline should work in a day or two and that I shouldn’t use anything else yet or it can be dangerous to give her too much.

I was also told her itching can be an allergy to something and that I should put flaxseed oil in her food. I did. I am feeding her fresh cooked chicken with brown rice and Dick Patten’s Natural Balance Allergy Formula. Help please!

Grace
Alhambra, California

I would wager that your dog is suffering from allergies to fleas.

Dogs with allergies usually suffer from skin and ear problems. Itching is the most common complaint.

Dogs can be allergic to thousands or perhaps millions of insects, pollens, food proteins, chemicals, and mammals (including cats and humans). But one thing is nearly certain: if your dog has allergies, she is allergic to fleas.

Flea saliva is phenomenally allergenic to cats and dogs (and some humans). This gives rise to a common paradox. Animals with flea allergies rarely “have” fleas.

The last time I visited Yosemite National Park, I suffered numerous mosquito bites. One day was particularly bad. I hiked in the Grand Canyon of the Tuolomne to a place that I will forever call the Mosquito Forest. I applied bug spray nearly constantly, but the six-legged parasites could not be held at bay. After about 15 minutes I retreated uphill towards my campsite.

I suffered about a dozen mosquito bites during my foray into the Mosquito Forest. I am allergic to mosquito saliva. That night, in my mosquito-free tent, I was miserably itchy. I was itchy the next day during my hike out of the wilderness. And the next day at work. And the next day, and the next day, and . . .

Dogs that suffer from flea allergies show similar symptoms. A week after my trek to the Mosquito Forest, there were no insects in sight. But I was still miserably itchy. A week after Frontline has eliminated the fleas on your dog, she too may be miserably itchy.

You have two choices in this sort of situation. If your dog’s condition is tolerable, you and she can wait it out (that’s what I did, and I’m fine now). If your dog is in severe distress, you can look into getting a cortisone shot or prescription.

Cortisone (a steroid, also known as prednisone) almost certainly will relieve the itching. But it is a strong medicine with many potential side effects. Consider the risks and the benefits carefully before giving her steroids. If she truly is miserable, the benefits probably outweigh the risks.

Photo: the Tuolomne River rolls into the Mosquito Forest at the base of Waterwheel Falls.

See related Vet Blog entries:

• New Website is Better Than Sliced Bread!
• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• Can Any Oral Medication Prevent Ticks, Fleas, and Heartworm
• Do Tapeworms Cause Itchy Rears?
• How Can I Know What is Causing my Dog’s Allergies?

My dog is about eight years old and his throat area is enlarged, like really big. It doesn’t really feel like a lump it feels more like his actual throat is swollen. Could it be his thyroid?

Tracie
Orangevale, CA

There are many things that can cause the throat of a dog to swell. All of them require prompt veterinary attention. Swelling in the area of the throat can compromise swallowing and breathing with disastrous results.

Allergic reactions to insect bites or vaccines may cause sudden swelling of the throat. Untreated allergic reactions can progress to shock, suffocation, and death.

Trauma to the throat can cause swelling. Sudden jerks to the collar or other blunt forms of trauma may lead to the symptoms you describe. Penetrating trauma can occur when dogs impale themselves or chew on sharp objects, leading to swelling in the affected area.

Infections in the throat may lead to swelling. Wounds from fights may cause abscesses (severely swollen infected areas). Foreign objects such as foxtails can lodge underneath the skin or in the trachea or esophagus, leading to infected, swollen areas.

Problems with salivary glands sometime lead to throat swelling.

Unfortunately, cancer is a common cause of swollen throats in older cats and dogs. Lymph nodes in the throat may be infiltrated with cancer, causing them to enlarge.

Thyroid disease is common in eight-year-old dogs. However, it does not lead to swelling of the throat.

Your dog should go to the vet. Hopefully the problem is not serious.

See related Vet Blog entries:

• Alarming Diagnoses Lead to Concerns of Cancer Epidemic
• Canine Lymphoma Treatment Takes Big Step Forward
• Does Methamphetamine Cause Cancer in Cats?
• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• Why is my Dog Still Itchy After I Applied Frontline?

My cat is 1 yr. old and she keeps sores directly
behind both ears, she also scratches this area
alot. She has had this case since she was a
kitten. What causes sores in this area?And could
this be some sort of fungal issue?

Angela
Maysville, GA

Several syndromes can cause skin lesions adjacent to the ears.

In kittens and young adult cats, ear mites are common culprits. Ear mites, as the name implies, infest the ears. They cause excessive ear wax production and make the ears intensely itchy. Affected cats sometimes scratch so fiercely that they traumatize the skin behind their ears.

Ear infections and foreign objects (such as foxtails) lodged in the ears may cause itching and self trauma as well.

Allergies can cause skin problems. Cats that are allergic to food, fleas or environmental agents such as pollen or detergents may develop sores on the face or head. Rarely, autoimmune syndromes can cause sores in the areas you mention.

Finally, skin infections with bacteria or fungus can cause hair loss. In particular, a fungal infection called ringworm often strikes young cats on or near the ears. Ringworm is contagious to people.

Your cat needs to see a veterinarian. In most cases, vets easily are able to sort out the nature of problems such as you describe.

Photo: Mocha’s ears and face look healthy.

See related Vet Blog entries:

• How Much and How Often Should I Feed my Dog?
• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• How is Ringworm Diagnosed?
• How Can I Determine the Age of my Cat?
• Why do Puppies and Kittens Produce so Much Waste?

I have a lovely Shepherd/Retriever mix who suffered
with dreadful ear infections for years until the
fifth vet we saw finally sorted out it was
allergies. She is now on Hill’s prescription low
allergen z/d and doing very well on it.

BUT I see on this website alot of
critique of this food. Can you advise what is or
is not in it that makes it tolerable to allergic
dogs? More protein? Less protein? More wheat or
less? Hard to know if I should switch or what to
switch to.

Maggie-Lee
Christchurch, New Zealand

Two subjects tend to inspire fanaticism among people who have pets: food and vaccines. It makes sense if you think about it. Both subjects are complex enough to prevent any person from proving, definitively, that their diet or vaccine protocol is the best. I have covered both subjects several times on this blog. Click here, here, here or here to read some food-related articles. Click here, here, here, here, here, or here to read about vaccines.

No doubt about it, plenty of people believe that Hill’s z/d is manufactured by Satan himself in the bowels of Hell. But z/d isn’t even remotely unique in that regard. If you doubt that, I challenge you to pick a food, any food, and google it. I guarantee that someone, somewhere, believes the food you have picked is produced by Satan or his henchmen.

Let’s step back from satanic associations for a bit and try to suss out what’s going on with your dog. Ear infections in dogs often are related to allergies. Dogs can be allergic to many different substances. Food is one of the many substances to which dogs may be allergic. Therefore, switching your dog to a hypoallergenic diet may help his ear infections.

Dogs with food allergies react to the proteins in their diets. Wheat protein is a common cause of troubles, but it is hardly the only one.

There are two ways to make a hypoallergenic diet. A manufacturer can use “novel” protein sources such as duck, fish or rabbit combined with egg or potato. Or, a manufacturer can use chemical reactions to modify the protein in the food so allergic individuals do not react to it.

Hill’s z/d employs the second tactic. The proteins are hydrolyzed, or broken down, to a size that makes them unlikely to cause allergic reactions.

Hill’s z/d is balanced and nutritionally replete. However, it is hardly the most natural diet out there. I certainly wouldn’t be willing to eat a food in which all of the proteins had been hydrolyzed. Nonetheless, I could survive on one.

If feeding a natural diet is a priority for you, then z/d isn’t the best choice. You can talk to your vet about alternative hypoallergenic diets.

However, remember that plenty of dogs thrive on z/d. If it is the only diet that works, it’s probably better for your dog than the pain and stress of chronic ear infections.

Photo: Checkers has no known history of ear infections. But he has fantastic ears.

See related Vet Blog entries:

• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• Does Pet Food Cause Health Problems?
• How Much and How Often Should I Feed my Dog?
• Consumer Reports Discusses Dog Food and Cat Food
• Can Cats Eat Dog Food, and Vice-Versa?

Our four-year-old Pitbull Racquel has been suffering
from severe allergies for more than a year now.
She is constantly on medication however it does not
seem to be getting better; worst of all, we do not
even know what is causing the the break out! How
can we find out exactly what Racquel is allergic
to? Desperately needing your
advice…

Cynthia
Brooklyn, NY

In dogs, allergies most often cause skin and ear troubles. Three main types of allergens cause a majority of problems.

Flea saliva is the most common allergen in dogs. Dogs with flea allergies almost never are infested with fleas. Fleas can be taken out of the picture with high-quality preventatives available from your vet. If the symptoms improve, then fleas may be playing a role in the problem.

Food allergies also are common in dogs. Special hypoallergenic diets are available. If the symptoms improve after you switch to one of these diets, then food may be playing a role in the problem.

The third group of allergens consists of environmental agents. These include pollen, mold spores, detergents, chemicals, and danders (dogs can be allergic to cats and to humans). To find out which of these agents may be playing a role in Racquel’s symptoms, you will need to run tests.

Blood allergy tests are available through many vets. Blood allergy tests are capable of detecting reactions to common allergens including fleas, foods, and many different environmental agents.

Special skin allergy tests (similar to those that are sometimes run in humans) are available through veterinary dermatologists. These tests check for skin reactions to a number of allergens.

If Racquel undergoes either type of testing, you may get the answers you are looking for.

Regardless, please remember that allergies cannot be cured. And, as you have already discovered, animal allergies tend to be very frustrating for pets and people.

To read more about canine allergies, check out my website:

http://drbarchas.com/canine_allergies

Photo: Mighty Midas is scratching, but I don’t think he has allergies.

See related Vet Blog entries:

• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• Why is my Dog Still Itchy After I Applied Frontline?
• What Makes Hypoallergenic Diets Special?
• New Website is Better Than Sliced Bread!
• Why are all of the dogs in America suddenly itching?

I have a one-year-old Yorkie female, unfixed, who is
losing the hair around her eyes.
Last month I put her on Comfortis for fleas.
I have not changed her food.
What can be causing this and what can I do ?

Jude
Union Springs

I suspect that your dog is suffering from demodicosis, or puppy mange. You can find out all about it on my new website.

http://drbarchas.com/demodex

What can be causing my dog to constantly lick her
paws and backside?

Jessica
Woodbridge, NJ

Excessive licking usually is caused by itching. What you ask, causes itching in pets? That information is available on my new website. Check it out!

http://drbarchas.com/itching

My nine-year-old mixed breed dog Panda has for the
last couple of years developed a sort of facial
tic – her lower jaw will jerk up and down as if
she was cold and chattering her teeth. She does it
more and more frequently and I’ve even noticed
her doing it in her sleep. Should I be concerned?

Terry
Chattanooga, TN

I don’t think you should be concerned. Jaw chattering usually is a form of trembling. Read all about it on my new website.

http://drbarchas.com/trembling

Dear Dr. Barchas,
I have two miniature Dachshunds. They are mates,
and they are both 10 years old. They are obese.
The male, George, weighs 20 pounds, and the
female, Gracie, weighs 19 pounds. They are both
trained to relieve themselves outside. They very
rarely ever make a mess inside the house unless
we have to leave them home alone for some reason,
although we always try to take them with us when
we go somewhere as much as possible. I have
noticed in the last couple of weeks that Gracie
has begun to urinate in the house, and in our
vehicle. She has NEVER done this before! Both
George and Gracie sleep with us at night, in our
bed. I have had to wash our sheets about four times
in the last two weeks because she has urinated on
our sheets and covers. Do you know what would be
making her do this? Should I be alarmed and take
her to her vet, or is it just because she is
getting older? Thank you so very much!
Sincerely,

Sherry
Louisville, Tenn.

Do I even need to say it? Read about inappropriate canine urination here:

http://drbarchas.com/canine_housesoiling

And read about canine obesity here:

http://drbarchas.com/canine_obesity

Please always feel welcome to search my website for answers to your pet-related questions. It’s completely free! Everyone is also welcome to enjoy the photo galleries, and to submit photos of your own to

petpeoplephotos@yahoo.com

for publication on the site. By submitting photos you grant me the right to publish them.

See related Vet Blog entries:

• Why Does my Dog Have Patchy Bald Spots?
• Why do Pets Twitch When Their Skin is Touched?
• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• Why is my Dog Still Itchy After I Applied Frontline?
• Why do Cats Urinate Outside of the Box?

What would cause a dog’s head to swell and bumps to develop
all over her back & sides?

Doddie
Abilene, TX

Acute allergic reactions commonly cause the symptoms you describe. Insect bites or stings frequently lead to facial swelling and welts on the body. However, anything that stimulates the immune system can cause the same symptoms. Sensitive individuals may react to pollen, certain foods, detergents, chemicals or vaccines.

Acute allergic reactions are potentially life-threatening. If the tissues of the throat swell along with the face, breathing can be compromised. In rare cases, facial swelling and hives on the body can be precursors to shock.

Any pet that suddenly develops hives or facial swelling should see a vet immediately on an emergency basis. Injectable medications usually can reverse the symptoms and prevent more serious consequences.

Photo credit: Gonzalo Rivero.

See related Vet Blog entries:

• What are the Possible Adverse Effects of Bee Stings in Cats and Dogs?
• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• Why is my Dog Still Itchy After I Applied Frontline?
• Why is my Dog’s Throat Swollen?
• What Makes Hypoallergenic Diets Special?

My eight-month-old female English Mastiff has spots of
hair loss on several places on her body. Our vet
tested her for mites. She doesn’t have any.
Tested her thyroid, it’s normal. He thinks it
might be a food allergy to chicken and corn, so he
changed her food from [a major commercial brand
to a hypoallergenic formula]. I add a little
canned food to her dry food and also use the
canned food to make her treats. She doesn’t
scratch herself excessively. Do you think we’re
on the right track to resolve this problem? I
would appreciate any advice you can give us.

Thank you,

Betty
TX

Based on your description of the spots (multiple spots, not itchy or inflamed), my first guess would have been puppy mange (also known as demodectic mange) is to blame. I wrote a somewhat extensive article on the topic a while back. You can read it by clicking here.

The test for puppy mange (called skin scraping) is pretty reliable. Nonetheless, in rare instances the test does fail to detect the mites involved in the syndrome. So one thing I recommend is that you keep puppy mange in the back of your mind as a possibility.

Certainly allergies (to food, pollen, fleas, or other environmental stimuli) can cause hair loss. But they usually cause itching and red skin as well. Thyroid problems can cause hair loss, but they are extremely rare in young dogs.

In my opinion, you have a couple of choices. The most aggressive tactic would be to perform biopsies of the affected areas. Samples of affected skin can be removed and sent to a laboratory for analysis. Biopsies are highly likely to lead to a diagnosis.

However, I’m not sure it’s necessary to go that far. If the bald spots are small and aren’t causing any irritation, it may be reasonable to take a wait-and-see approach.

Consider your dog’s age. An eight-month-old Mastiff is roughly equivalent to a 13-year-old person. Many 13-year-olds have acne. The blemishes associated with acne occur because the immune system is not fully matured. At this age, the immune system has a habit of over-reacting to some problems and under-reacting to others. The result is acne.

Your dog does not have acne per se. However, there is a very good chance that her patchy baldness is related to her immature immune system. If you wait a few months, the problem may resolve as her immune system matures.

See related Vet Blog entries:

• New Website is Better Than Sliced Bread!
• Why Does my Dog Have Patchy Bald Spots?
• New Labeling for ProMeris Offers Hope for Simple Puppy Mange Treatment
• What can I do About Intractable Puppy Mange?
• How Much and How Often Should I Feed my Dog?

I have a white pit and he seems to have allergies.
he breaks out all over his stomach and neck and
then scratches till he nearly draws blood. My vet
says to give him Benadryl. I’ve only given it to
him twice. What is your opinion on this?

Bonnie
Hazen, Arkansas, AR

My opinion depends on your dog’s response to the Bendadryl. Some allergies in pets are well controlled by Benadryl and similar over-the-counter antihistamines. Others are not.

Benadryl (diphenhydramine) is the most commonly recommended over-the-counter allergy medicine because it has a high margin of safety (although new concerns are arising about a link between Benadryl and cognitive decline in humans), and overdoses are rare. But in my experience, few pets experience dramatically reduced symptoms as a result of the drug.

If Benadryl does a good job of controlling your dog’s symptoms, then it probably will be the best bet for dealing with the problem.

If Benadryl doesn’t have much of an effect, then you may have to look into other treatments. The blog’s search function will help you find more information about hypoallergenic diets, allergy testing, allergen avoidance, flea control, omega-3s, and more potent medicines for allergies such as Atopica, Genesis, and prednisone.

Remember above all that allergies are impossible to cure. However, if you manage your pet’s problems properly, he should be able to live comfortably.

See related Vet Blog entries:

• Which Ingredients are Most Likely to Cause Food Allergies in Dogs and Cats?
• Why is my Dog Still Itchy After I Applied Frontline?
• Why is my Dog’s Throat Swollen?
• What Makes Hypoallergenic Diets Special?
• How Can I Know What is Causing my Dog’s Allergies?