Allergies in dogs
What is an allergy?
An allergy is a state of over-reactivity or hypersensitivity of the immune system to a particular substance called an allergen. Most allergens are proteins from plants, insects, animals, or foods.
Exposure to the allergen, usually on multiple occasions spanning months to years, sensitizes the immune system, and a subsequent exposure to the same or related allergen causes an over-reaction. Normally the immune system protects the dog against infection and disease, but with allergies, the immune response can actually be harmful to the body. Allergies may be thought of as an unnecessary normal immune response to a benign foreign substance. The immune reactions involved in allergies are quite complex. Most reactions involve allergen protein molecules combining with antibodies in the blood, then attaching to a type of cell called a mast cell. Mast cells are found in many tissues throughout the body. When the antigen and antibody react with mast cells, the mast cells release potent chemicals, such as histamines, that cause local inflammation such as redness, swelling, and itching. This inflammation causes the various signs associated with an allergic reaction.
What are the symptoms of allergies in dogs?
In the dog, the most common symptom associated with allergies is itching of the skin, either localized (in one area) or generalized (all over the body). In some cases, the symptoms involve the respiratory system, with coughing, sneezing, and/or wheezing. Sometimes, there may be runny discharge from the eyes or nose. In other cases, the allergic symptoms affect the digestive system resulting in vomiting and diarrhea. It can also be licking, face rubbing, red skin, loss of fur, or recurrent skin and ear infections.
How common are allergies in dogs?
Unfortunately, allergies are quite common in dogs of all breeds and backgrounds. Most allergies appear after the pet is six months of age, with the majority of affected dogs over age one or two. In fact, they are one of the top reasons for veterinary appointments. While humans often outgrow allergies, allergies in dogs tend to worsen as they get older. Dog allergy symptoms more commonly affect the skin and ears.
Are allergies inherited?
Within Veterinary Medicine it is well accepted that allergic skin disease in dogs has a hereditary basis. Or at least, there exists predisposition towards allergic skin disease with certain breeds of dogs. This underlying inherited basis may have a complex pattern of inheritance. However, that said, multiple genes may be involved. Certain breeds, such as Terrier and Retriever breeds, have a higher probability of developing certain allergies. Having one or more parents that has developed allergies increases the chances that your pet will also have an allergic reaction. Some allergies are thought to be inherited. An inherited allergy is atopy or allergies to pollens and plants (*see "What is inhalant allergy (atopy) and how is it treated?" below).
Is There an Allergy Test for Dogs?
Allergy testing in dogs is done for seasonal/environmental allergies only. Studies have shown that blood testing and skin testing for food allergies are not accurate in dogs.
Prior to performing allergy testing, your veterinarian should rule out other causes for your dog’s allergy symptoms. Allergy testing should not be used to confirm that your pet has seasonal/environmental allergies, but to determine the specific things to which your dog is allergic.
Studies have shown that hair and/or saliva testing for seasonal/environmental allergies or food allergies in dogs is not accurate.
Seasonal/environmental allergy testing can be performed in dogs by either skin testing or blood testing. Skin testing is the most accurate type of allergy test, and it’s generally performed by board-certified veterinary dermatologists. Mild sedation is required. The fur is clipped in a small area, and a series of very small amounts of allergens are injected into your dog’s skin. The degree of the allergic reaction to each allergen determines whether your dog is allergic to it.
What are the common allergy-causing substances (allergens)?
A very large number of substances can act as allergens. Most are proteins of insect, plant, or animal origin, but small chemical molecules can also cause allergy. Examples of common allergens are pollens, mold spores, dust mites, shed skin cells (similar to pet allergies in humans), insect proteins such as flea saliva, and some medications.
What are the different types of allergy?
There are several ways of classifying allergies. Some examples of classifications include:
• Allergen - flea allergy, food allergy
• Route the allergen takes into the body - inhalant allergy, skin contact allergy, or food allergy
•Time it takes for the immune reaction - immediate-type hypersensitivity, also called anaphylaxis or shock, and delayed-type hypersensitivity
• Clinical signs - allergic dermatitis or allergic bronchitis
• Inherited forms - atopy or seasonal allergies
What is flea or insect bite allergy and how is it treated?
Insect bite allergy is the exaggerated inflammatory response to the bite or sting of an insect. Arachnids such as spiders and ticks, and insects including fleas, blackflies, deerflies, horseflies, mosquitoes, ants, bees, hornets and wasps, can cause an allergic reaction in sensitive dogs. Flea saliva is by far the most common insect allergen in dogs, causing flea allergy dermatitis (FAD). Most dogs experience minor local irritation from flea bites. The FAD dog will react to a single bite with severe local itching. A dog with FAD will bite and scratch itself and may remove large amounts of hair, especially in the tail-base region. A secondary bacterial infection may develop in the areas of broken skin. Because one flea can be a problem for a dog with FAD, strict flea control is essential. This is difficult considering the life cycle of fleas, but modern monthly flea preventives and home treatment options allow you to provide a flea-free environment for your dog. Your veterinarian can give you tips on protecting your dog and other pets from fleas. When strict flea control is not possible, or in cases of severe itching, your veterinarian may prescribe antihistamines or corticosteroids (steroids) to block the acute allergic reaction and give immediate relief. If a secondary bacterial infection is present, an appropriate antibiotic will be prescribed.
*What is inhalant allergy (atopy) and how is it treated?
Also known as atopy, seasonal or environmental allergies are caused by substances that exist in your home, backyard, and anywhere else your dog spends time. The term inhalant allergy in the dog is often used as a synonym for atopy. The main inhalant allergens are tree pollens (cedar, ash, oak, etc.), grass pollens, weed pollens (ragweed), molds, mildew, and house dust mites. Many of these allergies occur seasonally, such as ragweed, cedar, and grass pollens. However, others such as molds, mildew, and house dust mites occur year-round. When humans inhale these aller gens, the resulting allergy primarily manifests with upper respiratory signs: runny eyes, runny nose, and sneezing (hay fever). Although sometimes the symptoms of allergies include allergic rhinitis or bronchitis, in most dogs, inhalant allergy manifests with itchy skin (pruritus). Due to these clinical signs, the condition is also called inhalant allergic dermatitis. The dog may rub its face, lick its feet and scratch the axillae (underarms).
Most dogs that have inhalant allergy start showing signs between one and three years of age. Affected dogs will often react to several allergens and often experience concurrent flea or food allergies. If the offending allergens can be identified by intradermal skin tests or blood tests, the dog should be protected from exposure to them as much as possible. Because most of these allergens are environmental, this is difficult and recurrent bouts are likely. Symptoms of atopy can be controlled but a permanent cure is not usually possible.
Treatment depends largely on the length of the specific allergy season. It may involve one or more of the following three therapies:
Anti-inflammatory therapy. Treatment with anti-inflammatory drugs such as corticosteroids, or with antihistamines, will quickly block the allergic reaction in most cases. Fatty acid supplementation of the diet can improve the response to steroids and antihistamines in some cases. Newer alternatives exist to block specific chemical signals associated with itch in dogs. These drugs include daily oral medications, such as oclacitinib (brand name: Apoquel®), and long-acting injections, such as Cytopoint®. Your veterinarian can help you determine whether these medications may be appropriate for your dog.
Shampoo therapy. Frequent bathing with a hypoallergenic shampoo can be soothing to itchy, inflamed skin.
Hypo sensitization or desensitization therapy.
If the specific offending antigens are identified by allergy testing, an allergy injection serum or allergy shots can be given to the patient. With this treatment, very small amounts of the antigen are injected weekly. This repeated dosing has the objective of reprogramming or desensitizing the immune system. Success rates vary with this treatment. Approximately 50% of treated dogs will see significant improvement in their clinical signs, while approximately 25% more will see a decrease in the amount or frequency or corticosteroid usage.
What is food allergy and how is it treated?
Food allergy or food hypersensitivity can develop to almost any protein or carbohydrate component of food. It most commonly develops in response to protein of the food; dairy products, beef, wheat gluten, chicken, chicken eggs, lamb, and soy are commonly associated with food allergies in dogs. Food allergy can develop at almost any age. Food allergy may produce any of the clinical signs previously discussed including itching, digestive disorders, and respiratory distress. A dog may have multiple types of allergy, such as both food allergy and atopy making the exact diagnosis of a dog’s itching quite challenging.
Food allergy typically does not respond well to corticosteroids or other medical treatments. Treatment requires identifying the offending component(s) of the diet and eliminating them. The most accurate way of testing for food allergies is with an elimination diet trial using a hypoallergenic diet. Because it takes at least eight weeks for all other food products to be eliminated from the body, the dog must eat the special diet exclusively for eight to twelve weeks. If a positive response and improvement of your pet's clinical signs occurs, your veterinarian will advise you on how to proceed.
It must be emphasized that if the diet is not fed exclusively, a food trial will not be a valid test. All table food, treats, and flavored vitamins must be discontinued during the testing period. There may be problems with certain types of chewable tablets or medications such as heartworm preventive. Your veterinarian will discuss the specific diet and restrictions recommended for your dog.
What is contact allergy?
Contact allergy is the least common type of allergy in dogs. It results from direct contact to allergens, such as pyrethrin's found in flea collars, pesticides used on the lawn, grasses, materials such as wool or synthetics used in carpets or bedding, etc. Contact allergies can develop to practically anything and at any age. If the dog is allergic to any of these, there will be skin irritation and itching at the points of contact, usually the feet and stomach. Removal of the allergen, once it can be identified, often solves the problem.
Caution:
The symptoms of allergies can be confused with other disorders, or occur concurrently with them. Therefore, do not attempt to diagnose your dog without veterinary professional assistance. Be prepared for your pet to receive a full diagnostic evaluation to rule out other causes of itching and skin problems. If an allergy is diagnosed, your whole family must follow your veterinarian's advice very closely in order to successfully relieve your pet's discomfort.
By Catherine Barnette, DVM; Ernest Ward, DVM, Leigh Burkett, DVM
Allergy Symptoms in Dogs
Allergies Manifest As:
Itching
Infections of the skin and ear
Hot spots
Chronic Diarrhea and /or IBD (inflammatory bowel disease)
Vomiting
Seizures
Behavior Problems / hyperactivity
Pancreatitis
Chronic liver disease
Lethargy
Cancer
Swelling
Swollen eyes
Irritation to the skin
Slide is per Dr. Khalsa National Canine Health Symposium
What every pet owner should know about food allergies
“Allergen-free dog food“ stouts one product website, while another company advertises “limited ingredient diets”. And the majority of companies that make grain-free diets suggest that they may be helpful for pets with allergies. How true are these claims, though?
As it turns out, food allergies are not as common as many pet food companies and websites may like for you to think. And while food allergies are one possible cause for your dog’s itchy skin and ear infections or your cat’s diarrhea, there are many more likely causes which may have nothing to do with the food.
What is a food allergy?
Food allergies occur when an animal’s immune system misidentifies a protein from a food as an invader rather than a food item and mounts an immune response. The end result of this response can be itchy skin or ear and skin infections in some pets, while it may cause vomiting or diarrhea in others. Some unlucky pets will have both skin and gastrointestinal symptoms. However, food allergies have to be distinguished from numerous other more common causes of these issues.
What are other causes of gastrointestinal signs in dogs and cats?
There are dozens of causes of gastrointestinal issues in dogs and cats – parasites, viruses, bacterial infections, pancreases, eating something they shouldn’t, and many others. For pets that have symptoms only on certain diets, it could be due to a food allergy, but it could also be due to an intolerance – the food may have too much fat, too much or too little fiber, or have other properties or ingredients that don’t agree with that particular pet, but aren’t due to an allergy. Your vet can help you figure it out.
What are other causes of itching, and skin and ear infections?
The most common cause of itching, skin infections, and ear infections in both dogs and cats are fleas, allergies to fleas, and environmental allergies – dust mites, pollen, grasses. Both flea allergies and environmental allergies are MUCH more common in pets than food allergies but flea, environmental, and food allergies can all have similar symptoms.
Diagnosis of food allergies
One of the most frustrating things about food allergies is that there really isn’t an easy test. While many tests – using blood, saliva, and even hair – that can be performed a veterinarian or purchased by a pet owner online (and even some times shockingly, through a Groupon!) advertise that they can diagnose food allergies or “sensitivities”, there is no proof that they work. None of the currently available tests have been shown to be accurate – that non-allergic dogs test negative and allergic dogs (and only allergic dogs) test positive. In fact, multiple studies (including this one just published) have shown that these kinds of tests are not very helpful in diagnosing food allergies, despite their widespread use for this purpose. Research results presented at a veterinary dermatology (skin) conference even showed that some tests “diagnosed” plain water and stuffed animal “fur” as having food allergies.
The “gold standard” or best method that we currently have, for diagnosing food allergies is the dietary elimination trial. This means feeding your pet a diet purchased through a veterinarian or carefully made at home that contains only a few ingredients (typically one protein and one carbohydrate plus necessary fats, vitamins, and minerals) that your pet has never been fed before or that are hydrolyzed (where the proteins are broken down into very small pieces that can hide from the immune system) or purified to remove the parts that are likely to cause allergies. This diet is then fed as THE ONLY FOOD OR FLAVORED THING TO GO INTO YOUR PET’S MOUTH for at least a month but potentially several, depending on your pet’s history and type of issues. If your pet’s signs dramatically improve during the trial, then to confirm a food allergy, your pet then has to go back to the old diet again. A quick relapse is suggestive of an allergy to an ingredient in the old diet. You then go back to the test diet until things get better again before trying one ingredient from the old diet at a time until you identify the specific foods that trigger the problem. Many people switch diets and their pets’ signs improve, but they never re-challenge, so we can’t know if it was coincidence or the diet that actually helped the pet! We see this commonly when the seasons change – pet owners assume it was the diet that caused the improvement in their pet’s allergies when actually it is because seasonal allergens – such as certain pollens – are much reduced.
The “allergy diet” myth
There are no diets that are completely “hypoallergenic”, meaning that they will not cause allergies. The closest we have to this kind of a diet are the hydrolyzed diets that can be purchased through veterinarians. Dogs and cats can be allergic to pretty much any protein or carbohydrate ingredient that can be found in pet food. Feeding a diet with duck, kangaroo, lamb, or venison doesn’t prevent food allergies, it just makes it likely that if your pet develops one, it will be to that protein instead of something more common like pork or chicken. Likewise, there is no evidence that continually changing (rotating) diet ingredients prevents food allergies, but it definitely can limit diet choices to try to diagnose them (since every ingredient your pet has eaten before is no longer available to be used in a dietary elimination trial).
What foods are associated with the most allergies in pets?
While the overall percentage of dogs and cats that have food allergies is low, there are some ingredients that are associated with more of the confirmed cases than others. The most commonly reported food allergies in dogs and cats are chicken, beef, dairy, and egg (and fish for cats). There is nothing particularly special about these ingredients other than they have been the most common ingredients in pet foods for the past few decades, so both cats and dogs often have been exposed to them a lot. What surprises many pet owners is that grains are actually uncommon causes of food allergies – most pets are allergic to animal proteins! Yes, the occasional pet is allergic to a specific grain, or even another plant-sourced ingredient such as potato, or even carrot, but this is less common than an allergy to an animal protein. Unfortunately, this information doesn’t prevent hundreds of companies from advertising their grain-free diets as being good for pets with allergies. Many companies also advertise gluten-free diets for pets. Gluten allergies seem to be extremely rare in pets, having been clearly documented only in Irish Setter dogs, possibly in Border Terrier dogs, and never in cats.
Do I have to use a diet from my vet for a diet trial?
Many companies make over-the-counter diets that they market as being good for dogs with allergies, but they often don’t live up to the hype. Many of these so-called “limited ingredient diets” contain more than 1 protein and 1 carbohydrate source. They may contain fruits and vegetables, alfalfa, kelp, or other ingredients that could interfere with a diet trial. Even those that only have 1 protein and 1 carbohydrate as well as the necessary vitamins and minerals listed on the bag may still contaminated with other ingredients. Several studies recently have shown that large proportions of over-the-counter diets contain ingredients (admittedly sometimes in very small amounts) not listed on the label, likely due at least in part to the common industry practice of running one diet after another in the same manufacturing line at the factory, without a thorough cleaning in between (this is like human foods that are labeled as being made in a factory that also processes nuts – even though they don’t contain nuts, they could have nut residues). Because of the high risk of contamination for over-the-counter diets, we strongly recommend using a veterinary diet for your dietary elimination trial (either novel ingredient or hydrolyzed, depending on the individual pet) or a carefully prepared home-cooked diet be signed by a board-certified veterinary nutritionist. The best diets for a food trial have 2-3 ingredients plus fat sources (which are very low risk for allergies) and supplements. Diets for a diet trial should never include fruits and vegetables (unless a vegetable like a potato is one of the 2-3 ingredients), herbs, or ingredients such as kelp because they can make it hard to interpret the results if your pet doesn’t improve on the diet.
If your veterinarian diagnoses a food allergy using a dietary elimination trial with a veterinary diet or home-cooked diet, you may be able to manage your pet afterward with specific over-the-counter diets (once the specific allergen is identified), keeping in mind that you could see a flare-up if you unknowingly purchase a contaminated bag.
Clinical Nutrition Team
Posts authored by the Clinical Nutrition Service team are by Dr. Lisa M. Freeman, DVM, PhD, DACVN, Dr. Deborah E. Linder, DVM, MS, DACVN, and Dr. Cailin R. Heinze, VMD, MS, DACVN
