ABOUT THE DIAGNOSIS

In animals, itching is a sensation resulting from the stimulation of nerve endings in the skin that provokes the desire to scratch, rub, lick, or chew the area. Many disease conditions of the skin cause itching in pets, and often itching pets have more than one under- lying condition present at the same time. Allergies are a common cause of itching—pets can be allergic to substances in the environ- ment, such as inhaled pollen and dust, to food, or to parasites. In dogs and cats, allergy to any of these factors can cause itching. Bites of parasites such as fleas, mites, lice, ticks, and flies can be responsible for itching. Skin infections due to bacteria, ringworm fungus, or yeast commonly cause itching, and secondary infections are a common additional cause for greater itching in pets with allergies, fleas, and other primary skin disorders. Less commonly, certain immune-mediated diseases and some skin tumors may stimulate itching. In addition, boredom and anxiety can be factors in psychogenic disorders that involve excessive licking and chewing when no underlying skin disease is present.

Sometimes pets do most of their licking and scratching when their owners or family members are not present; in that case, the presence of itching must be deduced from the resulting hair loss and skin irritation. Cats sometimes groom themselves so excessively when the owner is not present that they remove all the hair from their bellies. Often the owner or family member believes the hair has fallen out, but microscopic examination of the hair shafts reveals that the hairs have been broken off by excessive licking or chewing.

DIAGNOSIS: Pinpointing the specific cause of a chronic itching problem can be challenging, especially since some animals have more than one underlying condition. For example, pets that have allergies tend to become allergic to multiple substances. The skin damage caused by scratching and chewing also predisposes the pet to secondary conditions such as bacterial and yeast infections, which themselves may cause even more itching. An itching pet may have allergies to fleas and to food and also have a bacterial infection of the skin at the same time. Treating only one of these problems may only partly reduce the itching. This demonstrates the importance of assessing the skin properly, usually with diagnostic tests (see below) to have a clear answer about the cause and therefore to choose the best treatment. If several problems are causing the itching, their effect is additive. Thus, if a pet has a chronic allergic reaction in the skin (atopic dermatitis), it is not al- ways possible to prevent exposure to all the substances that cause the allergic reaction, but rigorous parasite control and elimination of skin infections may provide sufficient relief.

A thorough medical history is an essential part of the diagnosis of skin diseases. This is because basic information and details based on what you have observed can be very helpful in determin- ing the probable cause(s) of itching. Your veterinarian will need information such as: How long has the itching been present? How old was your pet when the itching began? Is the itching seasonal (or was it initially), or rather does it occur year-round? What area of the body was first affected? Has it spread to other areas? How severe is the itching?

Because so many different skin problems can cause itching, diagnostic tests are used for determining the cause of itching. In this way, the problem can be more clearly identified so that the best treatment can then be started. Commonly used diagnostic tests include:

• Skin scrapings: a tiny sample of skin cells is collected by pain- lessly and superficially scraping the skin; the sample is placed on a slide and examined under a microscope; used for detect- ing microscopic infectious agents such as mange mites, yeast, and bacteria.
• Acetate tape preparations: tape is placed against the skin, and the material sticking to the tape is examined under a micro- scope; used for detecting some parasites and yeast infections of the skin.
• Fungal cultures: small clusters of hair are plucked from the edges of areas of hair loss and placed on a culture medium designed to grow and detect ringworm fungal organisms.
• Allergy testing: Two types of tests are used. In skin testing, small amounts of substances that commonly cause allergies are injected into the skin (intradermally), and reactions to the injections are monitored to detect hypersensitivity (allergic) re- actions to the specific offending substances in a particular A newer type of testing involves sending a blood sample to a laboratory that looks for the presence immunoglobulins (anti- bodies) that are involved in allergic reactions, but this form of testing is not considered quite as reliable as skin testing.
• Skin biopsy: a small sample of skin is taken using local anes- thesia (or less commonly, general anesthesia); the sample is sent to a pathologist for microscopic This test is used if other tests have not yielded a diagnosis, if the condition is not responding to treatment, or if immune-mediated skin disease is suspected.

LIVING WITH THE DIAGNOSIS

Some causes of itching are curable, such as ringworm infections and sarcoptic mange. Therefore, a major goal consists of identify- ing these problems when they are present so that the pet may be permanently relieved of the problem. However, the majority of pets brought to the veterinarian because of itching have chronic dis- eases that will require long-term management. Conditions such as allergies (very common) and immune-mediated skin diseases (un- common) require some form of lifelong treatment as described below. Many of these pets intermittently can develop secondary conditions such as bacterial or yeast infections that are treatable but may tend to reoccur. Control of these secondary conditions will provide much relief for an affected pet. Also, new problems may arise that worsen itching. For this reason, diagnostic tests should be repeated whenever a pet has a flare-up of itching.

Overall, the causes of itching cover a wide spectrum of sever- ity, and determining the cause of itching will also give an insight into expected outcome—cure versus lifelong treatment, for example.

TREATMENT

Treatment is extremely variable, since itching is only the symptom of the problem (“the tip of the iceberg”). Therefore, the medications and other treatment strategies chosen depend entirely upon the underlying cause of the itching and should be discussed with your veterinarian.

DOs

• If you have a chronically itchy pet, have an “emergency plan”— potentially involving certain medications that are useful short- term and act quickly, for example, to deal with flare-ups. Trial and error will often determine which treatment will work best for a specific pet.
• Topical ointments containing corticosteroids or anesthetics are often useful for localized areas of itching caused by certain processes, but detrimental for others—check with your veterinarian before using them.
• For overall itching, colloidal oatmeal shampoos or rinses often help reduce the itching for a day or Topical treatments and baths seem to make some pets even itchier, however. For these pets, a rinse with cool water sometimes helps reduce the itching temporarily.
• Consider having a second opinion from a veterinary dermatolo- gist if the problem is persisting or if the cause or treatment remains Your veterinarian can refer you to one of these specialists (directory: www.acvd.org).

DON’Ts

• Do not give oral corticosteroids (cortisone-type drugs), such as prednisone, to control itching without a diagnosis of the Corticosteroids can make some conditions, such as bacterial or ringworm infections, mite infestations, and others, worse instead of better and potentially cause permanent damage to the skin or even to internal organs.

WHEN TO CALL YOUR VETERINARIAN

• Any time persistent scratching, licking, or chewing occurs or if a chronically itchy pet becomes worse.

SIGNS TO WATCH FOR

• In addition to scratching, licking, and chewing, look for hair loss and red, inflamed skin. If this occurs despite treatment, the treatment may not be working, and a recheck or a second opinion is warranted.

ROUTINE FOLLOW-UP

• Depends upon the cause of the
• Discuss with your veterinarian at each

Other information that may be useful: “How-To” Client Education Sheets:

• How to Deal with Severe, Self-Inflicted Skin Erosions
• How to Prevent Licking or Chewing at the Skin
• How to Bathe a Dog or Cat Using Medicated Shampoo

Article source: From Côté: Clinical Veterinary Advisor, 3rd edition. Copyright ©2015 by Mosby, an imprint of Elsevier Inc.

ABOUT THE DIAGNOSIS

Pyoderma is an infection of the skin with one or more types of bacteria. Several types of bacteria normally live on the hair and surface of the skin of healthy animals without causing the animal any problems; they are called resident flora. However, if the ani- mal’s skin defense mechanisms are compromised (from self- trauma, such as wounds or scratching; foreign body like a thorn or splinter; other primary skin diseases; diseases that affect the whole body internally; or a weakened immune system), resident flora bacteria and other types of bacteria may multiply and pene- trate into the animal’s skin, causing pyoderma. Pyodermas are generally classified as superficial or deep. Most pyodermas are superficial, affecting the upper layers of skin and hair follicles, and therefore are easier to treat and eliminate. Deep pyodermas affect the deeper layers of skin, and sometimes the entire skin thickness and deeper, subcutaneous tissues. In contrast to superficial pyo- dermas, deep pyodermas can be associated with fever and gen- eralized illness. Usually, the deeper the infection extends into the layers of the skin, the more serious the infection and the longer the duration of treatment needed to eliminate it. Most cases of deep pyoderma are associated with an underlying cause, such that treatment must be aimed both at healing the skin and at the causative problem.

Veterinarians often diagnose deep pyoderma based on symp- toms, as well as microscopic evaluation of bacteria from an in- fected area (cytology). A bacterial culture and susceptibility test is usually recommended to aid the diagnosis and facilitate the effec- tive treatment of the infection. It involves taking a small amount of discharge or a tissue sample from the infected site and sending it to a laboratory to identify the type(s) of bacteria present and de- termine which antibiotics will be effective in treating the condition. Because most deep pyodermas are secondary to an underlying condition, it may also be necessary to perform additional tests (skin biopsies, blood tests, urinalysis, fungal culture, skin scrapings, allergy testing, etc.) to identify the predisposing factor(s). Radio- graphs (x-rays) may be helpful in detecting foreign bodies and also determining if an infection has spread to the bone(s).

LIVING WITH THE DIAGNOSIS

The more severe types of deep pyoderma include furunculosis, cellulitis, and subcutaneous abscesses. These conditions are often quite painful, and in severe cases, animals may develop a fever and become very ill.

FURUNCULOSIS: Furunculosis is an extension of a superficial pyoderma to involve the hair follicles (folliculitis). Furunculosis oc- curs when the infected hair follicles (some of the pores of the skin where hairs are rooted) rupture and spread the infection to the deeper tissues. This type of deep pyoderma generally affects the muzzle (nasal pyoderma), chin (acne or chin pyoderma), pressure points on the elbow, hock, or chest (callus pyoderma), and be- tween the toes (pododermatitis), although any area of skin may be affected. The affected areas of skin may develop hair loss, bumps (nodules), redness, swelling, ulcerations, bleeding sores, blood blisters, scarring, and even deep fissures, wounds, or nodules (granulomas) that ooze a watery-bloody or purulent (pus) dis- charge (fistulous tracts).

CELLULITIS: Cellulitis is an even deeper infection than furuncu- losis, involving the deepest layer of skin and the underlying sub- cutaneous tissues. The infection dissects and spreads between the layers of tissue. The affected skin may appear very dark and may become so delicate that it comes off (sloughs) on its own or when the wound is being cleaned, leaving a gaping open sore.

ABSCESS: An abscess is a focal infection that becomes walled off from the rest of the body; it becomes filled with pus (an ac- cumulation of white blood cells which fight off the infection, dead tissue, and bacteria). Abscesses are especially common in cats. Bacteria are usually introduced into the deeper layers of tissue from a bite or scratch wound. If the abscess is not treated (drained), it may rupture and ooze pus internally (dangerous to the immediate overall health of the pet) or externally (beneficial). Abscesses occur most often on the face, neck, front legs, and around the tail base and can be quite painful. The affected area is usually swollen, warm to the touch, and red. The animal may be lethargic, unwilling to eat, and have a fever, especially if the abscess contents are seeping internally into the bloodstream.

TREATMENT

Treatment of deep pyoderma can include one or more of the fol- lowing: administration of antibiotics (often continuously for several weeks to months because antibiotics take time to reach the outer- most layers of the skin), medicated soaks and baths, medicated shampoos, and topical therapies such as specific medicated oint- ments or creams. Successful management of deep pyoderma hinges on using the correct dose of an effective antibiotic for a long enough period of time and determining and treating the underlying cause. Surgery may be indicated to drain an abscess or in rare cases of localized deep pyoderma. It may be necessary to clip the animal’s hair in the affected areas for effective wound care. Your veterinarian may also dispense pain medication for comfort.

DOs

• Administer the antibiotics according to the prescribed amount and schedule.
• Use proper hygiene. Wear gloves when cleaning wounds.
• Consider having a second opinion from a veterinary dermatolo- gist if the problem is persisting or for the latest treatments Your veterinarian can refer you to one of these special- ists (directory: www.acvd.org).

DON’Ts

• Do not stop any medication unless directed to do so by your
• Do not use an over-the-counter or prescription ointment, cream, or any other medication without first consulting a vet- erinarian. Many of these products are either unhelpful or even toxic to cats and dogs.
• Do not miss your follow-up appointment even if the animal’s skin condition has improved; evaluating the skin when the pyo- derma has cleared may assist the veterinarian in determining an underlying cause.
• Do not give ibuprofen, Tylenol, or any other antiinflammatory or analgesic (toxic) without first consulting with your

veterinarian; several human antiinflammatories can be fatal to cats with even a single dose. Ask your veterinarian for pain medication for your pet if it has not been prescribed and you feel it is needed.

WHEN TO CALL YOUR VETERINARIAN

• If the pyoderma does not improve several days after initiating treatment or recurs after a full course of therapy.
• If the pet stops eating and/or becomes weak or
• If the discharge develops a foul odor or pockets of gas (emphysema) develop under the skin (crinkly feel to the skin).

SIGNS TO WATCH FOR

• A reaction to any medication(s), shampoos, or topical Symptoms may include vomiting, diarrhea, hives, abnormal behavior, increased itchiness, hair loss, dry skin, and inflamed (red) skin.

ROUTINE FOLLOW-UP

• Commonly 10 to 14 days after the initial diagnosis (sooner if severe); then as needed based on progress and underlying

Other information that may be useful: “How-To” Client Education Sheets:

• How to Deal with Severe, Self-Inflicted Skin Erosions
• How to Prevent Licking or Chewing at the Skin
• How to Bathe a Dog or Cat Using Medicated Shampoo

Article source: From Côté: Clinical Veterinary Advisor, 3rd edition. Copyright ©2015 by Mosby, an imprint of Elsevier Inc.

 Elimination diet trials can be tough! We’re here to help. The Canadian Academy of Veterinary Dermatology would like to share some information and tips about this very important diagnostic step.

Your veterinarian has reason to believe that a “cutaneous adverse food reaction” – which we will simply call a “food allergy” – might be playing a role in your dog’s skin or ear problems. By addressing this allergy, you can help your dog feel much better.

That’s the good news! The bad news is that there is no accurate skin or laboratory test for food allergies in pets. And a dog with a food allergy looks just like one with environmental allergies and might, in fact, have both. Currently, the only way to diagnose a food allergy is using an elimination diet trial.

The elimination diet trial (also called a “hypoallergenic” diet trial) is an 8-week test period when your dog can eat one thing, and one thing only: the food recommended by your veterinarian.

Any other food, even a tiny treat, can affect the results of the trial. To give your dog the best chance of responding, you must be 100% strict with the trial for the full 8 weeks. We know that this is easier said than done!

What happens during those 8 weeks? If your dog has a food allergy, you will see a gradual 50% to 100% improvement in his condition, depending on whether other allergies are present. After 8 weeks, your veterinarian may ask you to return to your dog’s regular food and treats to see if his symptoms return. This step is called a dietary challenge, and is only done after your veterinarian has reassessed your dog. The challenge is recommended because many other factors (medications, season changes) can contribute to your dog’s improvement during those 8 weeks.

We’re often asked the following questions:

I haven’t changed the food recently and my dog’s poops are perfect; could he still have a food allergy?
Yes! In fact, most dogs with food allergy have eaten their food 2 years or longer. And it’s very common for the allergy to affect only the skin or ears.

How common are food allergies? Estimates vary, but about 20% of dogs with allergic skin disease have a food allergy.

What could my dog be allergic to? Almost anything! Food allergy is an inappropriate reaction of the immune system against a normal – and perfectly safe – food ingredient called an “allergen”. The most common allergens are proteins in food, which are abundant in meats but also

found in grains, fruit, and vegetables. Common allergens for dogs include beef, dairy, chicken, and wheat. But there are many others!

What is an Elimination Diet?

Simply put, it’s any food that we think doesn’t contain the ingredients that your dog may be allergic to. Elimination diets, also called “hypoallergenic” diets, fall into two categories: novel ingredient diets and hydrolyzed diets.

A novel ingredient diet is made from foods that your dog has never eaten. This makes the ingredients new, or “novel”, to his immune system. The immune system usually tolerates these ingredients because there hasn’t been time for an allergy to develop. A novel ingredient diet can be veterinary kibble or wet food, or a home-prepared food, based on your veterinarian’s recommendation and your preference. Although they can be very effective, there are a couple of drawbacks to novel ingredient diets. It can be difficult to find ingredients that are truly novel if a dog has already “eaten everything on the Ark”.

And we suspect that in some cases, dogs can cross-react to ingredients that they have never eaten. For example, some dogs allergic to beef may show symptoms when fed lamb or venison, even if they have never eaten these meats.

A hydrolyzed diet is made with ingredients that are broken down (hydrolyzed) in a way to make them very small. These tiny fragments are so different from the full-sized protein that they are much less likely to trigger an allergy. So even if your dog has an allergy to soy, he might safely be able to eat a food made from hydrolyzed soy. Hydrolyzed diets can be a good choice in dogs that have eaten a wide variety of foods and treats.

In addition to being hypoallergenic for your dog, the food must also be one that he digests well and eats happily for 8 weeks. Each dog is different, so sometimes we have to try a few different foods before we get it right!

What treats can I give during a diet trial?

None, unless they are specifically made to accompany the recommended food. Don’t assume that treats with a hypoallergenic label will be suitable. Even the tiniest amount counts: the flavouring in a single monthly heartworm pill is enough to set off an allergy. Think of a child with a peanut allergy. Would you give them “just one” peanut? Want to show your dog some love during the diet trial? See the Tips for Elimination Diet Trials below.

These common items can be the reason for elimination diet trials to fail:

• cheese or other foods used to hide pills (even if labeled hypoallergenic)
• rawhides, bullysticks, antlers, and other chews
• flavoured toothpaste
• chewable or flavoured medicines
• fatty acids such as fish oils
• joint supplements such as glucosamine and chondroitin
• gelatin capsules
• unwashed dishes, bowls, and cutlery
• “just a tiny piece” of food for a treat
• food dropped on the floor (we’re looking at you, toddlers!)

Can I feed fruit or vegetables?

Fruit and vegetables can sometimes cause allergic reactions too. Don’t assume they will be OK. Set your dog up for success by being as strict as possible!

Can I use a pet store food to diagnose a food allergy? How about a grain-free or raw diet?

We recommend using veterinary diets or home-prepared foods for the elimination diet trial. Studies show that some store-bought foods can contain small amounts of ingredients not listed on pet food labels, making them unsuitable for the 8-week elimination diet trial period.

Grain-free diets are not effective for elimination diet trials unless your dog only has a known grain allergy. And because we rarely know what your dog is allergic to when we start the diet trial, we would miss many food allergies by simply switching to a grain-free diet.

Raw foods are not recommended for diet trials. They don’t work any better than their cooked counterparts, and pose health risks to your dog and your family.

Will I need to feed the recommended diet forever?

In most cases, no. Even if your dog has a food allergy, your veterinarian can often recommend foods other than the trial diet that will work for long-term feeding. And of course, if your dog does not improve by 8 weeks, there is no reason to continue the food.

Why is the diet trial so long?

It takes a long time for the skin to normalize after a food allergen is removed. A diet trial lasting 8 weeks will diagnose about 95% of food allergic dogs. On the other hand, a trial lasting 4 weeks will diagnose only about half.

How can I find out exactly what my dog is allergic to?

If your dog reacts to his previous food or treats, you might wish to find out exactly which ingredients caused the problem. Your veterinarian can guide you through a sequential process (provocation) that involves adding individual suspected food allergens to the diet for up to two weeks at a time.

Tips for Elimination Diet Trials

• Tough love. You will need to be strong when confronted with those big brown eyes asking for a treat. Think of the possible health benefits for your dog. Or imagine a peanut-allergic child asking for a peanut butter cookie!
• Take it slow. Don’t switch to the new food overnight. It’s a recipe for refusal and stomach upset. Take at least one week (or longer) to make the transition, starting with a very small amount of the new food on day one. Start the 8-week countdown on the first day you feed only the elimination diet.

• Don’t give up. Though we always recommend a food that we think is best for your dog, what your dog actually thinks matters most. Call your veterinary team if you encounter food refusal, diarrhea, or any other Veterinary diets are guaranteed, so the food can be returned and replaced with another if your dog doesn’t like it.
• “Good dog!” Make the food into a treat by putting it into your dog’s cookie jar and using it as a reward. If your dog gets food from the kitchen counter or table, have a stash of the food at these locations. You can even hide it in a food-dispensing toy to make it more fun for your dog. As your veterinary team for other tips on rewarding your dog.
• No stealing! Feed your dog separately from other pets to make sure he doesn’t sneak into their bowls.
• Don’t mix and match. Stick to one type of food during the trial. For example, don’t add a venison canned food with a hydrolyzed dry food. No one food is 100% hypoallergenic for every dog, so feeding more than one type increases the chance of “missing” a food allergy.
• Oh no, pills? If you struggle to give oral medications to your pet, ask your veterinarian about alternatives such as injections or topically applied treatments, or even delaying the diet trial.
• Let your pack Your dog may have an entourage: children, neighbours, dog walkers, dog daycare staff, pet store staff, and
• Plan Purchase the food well in advance of when you will run out.
• Stay clean. Keep the food in its original packaging, or thoroughly wash the container you use for storing the food.
• Keep track. Keeping a calendar of your pet’s symptoms, medications, and food can really help us figure out what’s working, and what’s not.
• Don’t panic! If you make a mistake, it’s OK. Record it on the calendar and keep going with the diet trial.
• Stay strong. For the sake of your dog’s health, do your best to stick with the trial for the whole 8 weeks. Call your veterinary team with questions, or to ask for help.

Every dog is different. We know it takes patience and effort to complete an elimination diet trial. But if your dog has a food allergy, your persistence can make a world of difference to his quality of life. Hang in there!

Article source: Canadian Academy of Veterinary Dermatology Promoting the advancement of veterinary dermatology in Canada Visit us at www.cavd.ca