Food Trial, Canine

Food Trial Procedure

By Dr. Karen Burgess

There are two specific categories of hypoallergenic diets available. The first contains a “novel” or new protein and carbohydrate source. Since many dogs and cats have now been exposed to lamb, fish, and even venison, common proteins in these diets include duck, rabbit, and kangaroo. Clients often wonder why an over the counter limited ingredient diet is not a viable option. In a recent study three out of four commercial venison diets claiming to contain no soy, poultry, or beef tested positive for at least one of these antigens/proteins. Prescription novel protein diets are manufactured and tested rigorously to ensure no cross contamination.

The second form of hypoallergenic food is made with hydrolyzed protein which is a conventional protein (such as chicken or soy) that has been reduced to a moleculer size that the immune system cannot recognize and thus react to.

Some owners are interested in home cooked hypoallergenic diets. While a viable option, these diets tend to be more labor intensive and end up being more expensive than prescription diets. If using a homemade diet long-term it should be formulated specifically for your pet by a veterinary nutritionist.

Regardless of type of diet used, please consult with your veterinarian regarding appropriate feeding amounts.

Treat suggestions during a food trial:

• Blenderize food trial kibble with water and a little honey into a doughy consistency, ball up to treat size and store on wax paper in a refrigerated plastic container
• Canned version of food trial diet if available
• If using oat based diet, thick cooked Quik oatmeal with a little honey, store as above
• Kongs with food trial kibble or above dough on the inside
• If potato based diet, baked frozen French fries

Food Allergy, Canine

Food Allergy

By Dr. Karen Burgess

What is the difference between food allergy and food sensitivity?
Some pets have food sensitivity instead of a true food allergy. This is a situation where pets do not tolerate a particular food component but are not having a systemic allergic response. An example of a food sensitivity would be eating spoiled food or someone that was lactose intolerant.

What are common signs of food allergy?
The most common symptom associated with dog and cat food allergy is a non-seasonal itchiness that is not due to another cause such as parasites (i.e. fleas, mange). Typically these signs develop prior to one year of age and are non-responsive to steroid therapy. Common signs include recurrent ear infections, facial itching, and peri-anal itching. Repeated skin infections and hair loss may also be noted. Some pets will display gastrointestinal signs (vomiting, diarrhea, weight loss, flatulence) in addition to or instead of skin signs with food allergy.

How is food allergy tested for?
Clinical signs and history (in particular symptoms prior to a year of age) may be highly suggestive of a food allergy. The only true way to diagnose a food allergy is to perform an eight to twelve week food trial using a veterinary approved prescription hypoallergenic diet (see additional information below on Food Trials). If symptoms resolve this is a strong indicator that the pet is allergic to some component in their previous diet. After completion of the food trial, pets are challenged with individual proteins or carbohydrates to see when they again become symptomatic (typically within two weeks of re-exposure). The goal is to determine whether there is an over-the-counter diet that may be acceptable for long-term use. Owners may continue the hypoallergenic diet indefinitely as it can often be difficult to transition successfully to a commercial product. Some companies do offer blood testing for food allergies. These tests are notoriously unreliable with numerous studies showing both false negative and false positive results. An appropriately performed food trial is the only valid way of testing for a food allergy.

What are symptoms of conjunctivitis?
Mild cases of conjunctivitis may appear as increased tearing that is clear or colored in nature. More severe cases can develop swollen pink or red bulging tissue that appears to almost cover the eyeball. The eye may become increasingly painful causing a pet to hold it shut or paw/rub at eye. In severe cases it may be difficult to see any part of the normal eye.

Why do cats and dogs develop conjunctivitis?
There are numerous reasons for the conjunctiva to become inflamed. Infectious causes include viruses and/or bacteria. In some cases infections will develop secondary to some other underlying cause of conjunctival inflammation. For cats viral conjunctivitis is extremely common and closely related to upper respiratory viral infections they are exposed to at a very young age. In several of these situations the cat may recover from the initial infection but the virus remains dormant in their body reappearing later in life at times of stress or illness. Non-infectious causes of conjunctivitis are typically related to the anatomy (size, shape, and location) of the eyeball itself. Dogs often develop a condition where they stop producing tears which then leads to a “dry eye” and secondary conjunctivitis. Some breeds of cats and dogs are more prone to having flat faces or bulging eyes which can change how the eyelid sits against the eye. In these cases eyelashes or facial fur may rub against the eye and conjunctiva causing inflammation. Allergic disease, foreign material caught in the eye, tumors, and immune disease are all additional causes of conjunctivitis.

How is conjunctivitis diagnosed?
A veterinary examination will typically reveal the presence of conjunctivitis. Additional testing of the cornea and tear production may also be necessary. If systemic disease is suspected bloodwork may be recommended. In complicated cases referral to an ophthalmologist may be recommended.

What are treatment options for conjunctivitis?
Definitive treatment of conjunctivitis involves diagnosing the underlying cause for treatment and controlling secondary bacterial infections. This may involve topical drops or ointment, oral medications, eye lubricants, or surgery. It is important to protect the eye from self-trauma by using a protective collar or Elizabethean collar. Pain medication may also be prescribed to help with associated discomfort.

What is the prognosis with conjunctivitis?
Prognosis is directly related to the ability to treat the underlying condition causing the inflammation.

What are signs of atopy in pets?
The most typical presentation is itchy skin, secondary skin infections, and ear infections or inflammation. Symptoms may be seasonal in nature or year round depending on the underlying allergen. All areas of the body can be affected, but in dogs the face, armpits, abdomen, feet, and legs are often predominant. Dome pets may have a red color to their fur from licking (saliva contains a pigment that thus stains the fur). Cats can have lesions anywhere on their body. Ears are a continuation of the skin inside so infections are common secondary to atopic inflammation of the ears. Respiratory signs can occur in pets but are much less common. Symptoms often start between 1 and 3 years of age and will usually get worse over time not better thus making treatment essential.

What causes atopy?
Just like in humans, allergies are an inappropriate and excessive response of the immune system. Essentially instead of ignoring an allergen such as dust or mold, the immune system becomes overly excited at any exposure leading to inflammation of the skin for pets. Genetics also play a part with certain breeds having a higher incidence of atopy.

How is atopy diagnosed?
Clinical signs and history are very helpful in identifying atopy as a cause of chronic itching or skin disease. The first step is ruling out other causes of itchy skin, in particular parasites (mites, fleas, lice), secondary bacterial or yeast infections, and systemic diseases (hormonal diseases, cancer). The next step is determining whether food allergies may be a factor. Pets can experience both food allergies and atopy and symptoms for both overlap, but their treatment is very different. Once all other possible causes of chronic itching/skin disease have been ruled out then atopy is the most likely diagnosis and definitive testing can be performed. Skin (intradermal) testing has for years been considered the gold standard. Similar to in humans, an area of skin (typically on the side of the body that has been shaved) is pricked with a variety of potential allergens and the subsequent response is measured. This information is then used to create injections that are used for treatment. Prior to testing steroid and antihistamine therapy must be discontinued for a period of time. Sedation is necessary for skin testing. Blood allergy testing has become more reliable; this method measures the pet’s antibody levels toward a particular allergen.

How is atopy treated?
There are many ways to manage or treat atopy. A few are listed here.

1. Minimize exposure– Avoidance or removal of specific allergens (washing feet after going outside, frequent baths)
2. Hyposensitization (“allergy shots”)- Information obtained from allergy testing can be used to design specific immunotherapy. By giving small doses of allergens at a regular interval, the pet hopefully develops tolerance to them and thus reacts less when encountered in the environment. Unlike in humans, pets do not outgrow allergies like some humans. These injections are typically given by owners at home and are found to be effective in 75% of treated dogs.
3. Immune modulators– Atopica (cyclosporine) is a non-steroidal medication that alters how the immune system responds to an allergen. While safe and effective, this product can be expensive particularly for larger dogs. Corticosteroids (such as pred) act as an anti-inflammatory and immunosuppressive agent. While very effective at controlling symptoms and inexpensive, steroids have a myriad of negative side effect and are not a safe chronic long-term solution.
4. Antibacterial/antifungals– It is common for pets with allergies to develop secondary bacterial or fungal injections. In essence pets with allergies have “sick skin”. While bacteria and yeast are found naturally on the skin, it is easy for their numbers to get out of control for pets with allergies. For severe infections or overgrowth, oral antibiotics or antifungals may be necessary. In milder cases topical products may be sufficient.
5. Antihistamines– Commonly used to control allergy symptoms in humans, antihistamines such as Benadryl are far less effective in dogs and cats. The mechanism of action is to block the chemicals causing the itch (typically histamine). Any particular antihistamine may help only 10-15% of pets. Trial and error is necessary to determine which if any might be beneficial for an individual pet. Overall antihistamines offer a safe and inexpensive adjunct to atopy treatment.
6. Omega 3 supplementation– Often referred to as fatty acid or fish oil supplements, Omega 3s overtime can decrease the inflammation associated with atop. DHA and EPA are the common fish origin omega 3 fatty acids. When determining a dose the sum total of DHA and EPA is used with a target of 70 mg/kg/day (range 50-100 mg/kg/day). Fish oil supplements are a supplement and thus not well regulated. Reliable brands include Nordic Naturals (online human product) and Welactin (veterinary product).
7. Topical treatments– Shampoos, conditioners/lotions, and sprays can all be very useful in controlling allergic skin disease. Medicated shampoos need to be used frequently (two to three times weekly) and allowed to stay in contact with the skin for 10-15 minutes before rinsing. While for some clients this is not the most convenient therapy, it allows a relatively inexpensive at home treatment option that is safe and does not involve systemic (oral) medication. Sprays and lotions are used for specific or isolated areas. Steroid sprays allow the potent anti-itch effect without the same negative side effects of oral steroids.
8. Flea and tick preventative– Year round prevention of parasites is recommended to avoid this complication for the already itchy atopic pet.