Canine Allergies

One of the most common health issues facing French Bulldogs are allergies, and many breeders and owners are constantly looking for better ways to improve their dog’s quality of life and overall skin condition. There are many factors that influence allergies. Genetics, consistently breeding lighter colored or pied dogs together over several generations, as well as geographical location, are only a few of the reasons that contribute to the multi- factor problem.

Allergies in dogs and humans are a difficult problem to tackle. For many years the only solution was medication or hyposenstitization – exposure to a small amount of allergen and working toward a larger amount without creating a catastrophic reaction in the body. In an effort to better understand and treat these common problems researchers have made some interesting discoveries in their cause and helped to identify if a dog is truly “allergic” or can be diagnosed as “atopic.”

Atopic dermatitis in the French Bulldog seems to be contained to certain areas of the body. The face, feet and muzzle are the most affected areas. We have all seen the red feet, infected and swollen wrinkles in the muzzle, and the rash under the armpits and on the sparsely haired areas of the belly. In other breeds the distribution may be completely different and their causes may also be different. Presently, there is ongoing research to identify a defect in the outer layer of the skin, called the stratum corneum – the components that seal together the individual cells appear to be defective.

This defect allows bacteria and yeast easy access and makes this individual chronically susceptible to infection. Although the dog with this problem will always have issues, it is possible to develop a DNA test for the defect and breed responsibly to eliminate it from the bloodline. This is only one of the remedies being offered by modern medicine and science to combat this problem.

In order to recognize a dog with atopic dermatitis (AD), Dr. Claude Favrot, a professor and head of the Dermatology Service at the Veterinary Facility of the University of Zurich, devised a criteria. Favrot’s study involved a large group of geographically diverse atopic dogs. This study has produced the most valid set of criteria for diagnosing allergic dogs that the veterinary profession has to date This criterion has 85% sensitivity and 79% specificity, if five of the eight criteria are met.

all2 all1 The list of the criteria is as follows:
1. Age of onset less than 3 years
2. Dogs live mostly indoor
3. Corticosteroid-responsive
4. Chronic or recurrent yeast infections
5. Affected front feet
6. Affected ear pinnae
7. Non-affected ear margins
8. Non-affected back or lumbar areas

Interestingly, most of the dogs affected were indoor dogs. This is also consistent with the fact that as general hygiene improves, so do allergies in humans. Allergies are not a problem frequently encountered within populations living in third world countries. Allergies and allergic reactions seem to be more prevalent in sanitary and hygienic industrialized countries. Another fascinating correlation found that in humans, mothers that ingested probiotics during pregnancy and for five months after their baby was born, tended to have children with less allergic issues. This was even consistent when there was a substantial family tendency for allergies. Perhaps feeding bitches probiotics while pregnant and nursing will help to curb the hyper excitement of the immune system in their puppies.

While all these criteria from Favrot do have a high specificity and sensitivity, there will be dogs that will never have clinical lesions that are visible. These dogs can be some of the more difficult to diagnose and treat. This group of dogs are incredibly itchy and will have no pustules or visible dermatitis. Their only symptom is an uncomfortable itch.

What to do if you think your dog may have canine atopy?

If you think your pet has canine atopy seek professional veterinary counseling. Canine atopy is a diagnosis made using the following three elements and all are required for a proper clinical diagnosis; (1) compatible history, (2) compatible clinical signs, and (3) rule out all other causes of pruritis (itching and redness) that can mimic allergic dermatitis.

Items one and two above can be easily reached with a physical exam and a discussion of the criteria given above.

Demodex mite under a microscope

Demodex mite under a microscope

The next thing your veterinarian will likely do is a physical examination to make sure there are no fleas. A skin scrape will be done, eliminating parasites as a cause of your pet’s discomfort. The skin scrape will determine if the dog has mites. Demodicosis and sarcoptic mange can be very itchy and cause similar dermaological findings. In addition, dogs that are routinely treated with corticosteroids (prednisone and other like medications for allergies) can cause immunosuppression, which leads to a weak and compromised immune system. Under these conditions mites can become prolific and cause disease.

Other causes of pruritis that will need to be considered will be food allergy, staph and yeast infections. A quick cytology of the skin will provide your veterinarian with information as to what is living on your dog’s skin. Looking at a slide of a skin cytology or superficial scraping, yeast and staph infections can be easily seen. Depending upon the severity of the infection, your veterinarian may feel the need to do a skin culture. The difference between the two is this; cytology will tell you what is living on the skin (staph bacteria, yeast etc.) and a culture will identify the exact organism and the appropriate drug needed to effectively treat the infection. Many times, when infections are severe, there are more than one bacteria growing in a skin infection. When multiple bacterias are found in one location it is necessary to know exactly which drug will treat all the bacterial types that are found. This is essential to make sure all infection is cleared and to avoid resistant infections in the future.

What about Allergy Testing?

Sarcoptesscabie under a microscope

Sarcoptesscabie under a microscope

Allergy testing (of all types) do NOT answer the question “is this itchy patient allergic?” There are two types of allergy testing – using a blood sample, or with intradermal injections of allergens themselves. The blood test is easy to do and does not require a withdrawal from medication. The intradermal test was previously considered more accurate, but requires a patient to be off medication for weeks. In some cases this is just not feasible as some dogs cannot be withdrawn from their antihistamines and steroids due to severe discomfort. Most of the withdrawal times for these medications are several weeks.

Allergy testing should only be done if you are committed to making a vaccine specific for your dog and giving the injection every other day, working up to a once monthly injection for maintenance. The only other benefit of allergy testing is to glean some insight as to what your pet is allergic to and then to avoid it. For example, if your dog is allergic to cedar, you would not want to give him a cedar filled bed to lay on.

Allergy tests are much better now than in the past, but no test is perfect as all types of allergy tests will generate some false positive results. Conversely, you may have a dog that fits all the criteria and his testing is completely negative. These can be a real challenge and may need consultation by a board certified veterinary dermatologist.

Most allergic dogs have sensitivity to inhalants, contact allergens, food and flea allergies. They are all like wedges in a pie. The trick is to minimize all of them enough to make your pet comfortable. We have very good flea products presently, so that portion of the pie can be almost eliminated. As far as food allergy is concerned, there are quite a few foods that have a pulverized soy bean base that is small enough not to be recognized by the body’s immune system. These foods include Purina’s HA, Science Diet’s Z/D and Z/D ultra and Royal Canin’s brand of Hydrolyzed Protein HP food.

The key to good success is managing secondary infections, a good diet that works for your dog, and medication and/ or hyposensitsation to control the inhalant and contact allergens. Perhaps soon, we will have genetic testing to allow breeders one more tool in helping out with this frustrating disease.