An allergy is an abnormal reaction by the immune system against a normally harmless substance. In a pet with allergies, the immune system encounters the allergen or ‘trigger’, which the body sees as harmful. These allergens cause the immune system to produce a protein referred to as IgE, which then attaches to cells called ‘tissue mast cells’ located in the skin. When the IgE attaches to these mast cells, it causes the release of irritating chemicals such as histamines, which cause allergy symptoms. In dogs, these particular reactions and cell types are only present in significant amounts in the skin, which is why that is where we see a reaction and therefore allergy symptoms. In these pets their immune system is considered hyper-sensitive, reacting to things that in a normal pet would not cause a reaction. Allergies can affect dogs in a wide variety of ways – and not every dog will exhibit the same symptoms.
Allergies are among the most difficult conditions to diagnose and treat – understanding why and how allergies occur is the first step to treating a pet’s allergies.
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According to Dr. John Gordon, board-certified veterinary dermatologist at MedVet, chronic ear infections are nearly always allergy related. A change in diet will improve the symptoms in at least 30% of the allergy patients he evaluates.
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Dermal Effects – Dermal symptoms include itching involving the skin. This itching can be localized to a particular spot or can affect the pet’s entire body. Welts, bumps, redness, rashes, and hair loss are common manifestations of allergies. This is by far the most common form of allergy symptom. Ear infections are another common dermal symptom of allergies.
Allergies are perhaps one of the most difficult problems to effectively diagnose and treat. Allergies are often explored when all other potential causes – such as respiratory infection, virus, or parasites are eliminated.
Chewing on feet
Is your pet prone to allergies?
How will you know if your dog has or could develop allergies? Like humans, dogs and cats must be exposed to the allergen for some time before an allergy develops, giving the body time to mount its immune response – the dog’s body must learn to react to the allergen. In dogs, allergies may start at any age. Most, however, start to develop between one and three years of age. To make matters worse, as the dog ages, his response to allergens may become more severe, or he can develop allergies to additional things. In some breeds, an allergy is ‘learned’ and then genetically programmed, passing from generation to generation. Thus, allergies can be genetically linked. Allergies are more common in certain breeds such as Scottish Terriers, West Highland White Terriers, Lhasa Apsos, Bichon Frise, Maltese, Labrador and Golden Retrievers, Dalmations, Pugs, Sharpeis, Cocker Spaniels, Miniature Schnauzers, and English Bulldogs.
Types of Allergies in Pets
Allergens can take many forms: they can be inhaled like pollen and chemicals; they can result from physical contact, also known as contact dermatitis; and they can be ingested as in the case with medication or food allergies. There are several causes of allergies in pets – most notably Atopy – which is an environmental or inhalant allergy; contact and flea allergies; and food allergies and intolerances. There are numerous conditions which cause problems with a dog or cat’s skin, but the most common, by far, is allergies. Allergies can be a chronic problem, or episodic in nature.
Common allergens include:
A pet who is allergic to something will usually show its allergic reaction through skin problems and itching, or pruritus. It may seem logical that if a dog is allergic to something he inhales (atopy), such as pollen or grasses, he will have a runny nose; if he is allergic to something he eats (food allergy) such as beef or dairy, he may vomit; or if he has a contact allergy (contact dermatitis or flea allergy) he may have swelling and itching at the site of contact. In reality, dogs rarely have signs this specific. Instead, most allergies symptoms consist of mild to severe itching all over the body, whether caused by environmental or food allergies; some allergies are also characterized by chronic ear infections.
The dog may also show digestive symptoms - both a food allergy and a food intolerance can be characterized by vomiting, excess gas, or chronic diarrhea. Since the symptoms are the same for an allergy or intolerance, it is nearly impossible to know which your pet suffers from. Both are treated in the same manner by utilizing a food trial.
Managing Allergy Symptoms
How do I know what type of allergies my dog has?
The short answer is, you don’t! Intradermal skin testing is the method recommended by veterinary dermatologists and is practical and precise way to pinpoint your pet’s environmental allergies. Identifying the cause of a food allergy is often a system of trial and error; thus most dogs with allergies are managed in a multi-level approach - most allergies can be managed appropriately with a combination of avoidance, supplementation, medication as determined by your veterinarian, and food trials. Due to the fact that many other problems can cause similar symptoms, and that many times animals are suffering from more problems than just food allergies, it is important that all other problems are properly identified and treated prior to undergoing treatment for allergies. Flea bite allergies, intestinal parasite hypersensitivities, sarcoptic or demodectic mange, and yeast or bacterial infections can cause similar symptoms as both environmental and food allergies. All likely causes should be appropriately addressed by your veterinarian.
First Things First
Because there are so many variables in a pet’s environment, and many dogs with allergies have both food and environmental allergies, changing food is often an easy first step in helping manage allergy symptoms. It is estimated that food allergies plus atopy account about 50% of the causes of itching and scratching.
Food allergies can affect both dogs and cats, and unlike atopy there is no strong link between specific breeds and food allergies. Food allergies affect both males and females, neutered and intact animals equally. They can show up as early as six months of age to any time in life, though most occur between two and six years old. Many animals with food allergies also have concurrent inhalant or contact environmental allergies – thus, using a hypo-allergenic diet may alleviate symptoms dramatically, but it may not provide 100% improvement.
The symptoms of food allergies are similar to those of most allergies seen in dogs and cats. The primary symptom is itchy skin, often affecting the face, feet, ears, paws, armpits, and underside. Symptoms may also include chronic or recurrent ear infections, hair loss, excessive scratching, hot spots, and skin infections that respond to antibiotics but reoccur after antibiotics are discontinued. It is difficult to distinguish an animal suffering from food allergies from an animal suffering from atopy or other environmental allergies based on physical signs alone. However, there are a few signs that increase the suspicion that food allergies may be present.
• Recurrent ear infections, especially yeast infections
• Age of dog – a very young dog with moderate or severe skin problems is more likely to be suffering from a food allergy
• Allergy symptoms are year round, with change in seasons offering no relief to itchiness
• Allergy symptoms such as itching do not respond to steroid treatment
A food intolerance differs from a food allergy in that it is not a true allergy, thus there is no immune response from the body. Symptoms of a food intolerance are usually gastro-intestinal in nature, causing vomiting, excess gas, diarrhea, or chronic loose stool. Treatment of a food intolerance can be approached the same way as food allergy – with a food trial.
Food Trials and Elimination Diets
When a pet is suspected of having a food allergy, it is recommended they undergo a food trial. During a food trial, an animal is fed a diet consisting of a novel protein and a novel carbohydrate source that the animal has never eaten before. Remember, an allergen response requires repeated exposure, so feeding something the pet has never had before decreases the likelihood of an allergic response. Thus the ingredients that have been most common in pet food in the past are the most common culprits today. Common allergens in pet foods are beef, dairy products, chicken, turkey, egg, wheat, corn, and soy. These are the ingredients you should try to avoid! There are a number of limited ingredient diets available; such as, Herring & Green Pea, Duck & Potato, Venison & Potato, or Salmon & Rice. You should check carefully and read the ingredient listing to make sure your trial diet contains only those ingredients. Often times even though a product is labeled “Lamb & Rice”, it contains other ingredients like chicken or corn.
Veterinarians used to recommend that a pet only needed to be placed on a special diet for 3-4 weeks, but new studies show that in dogs, only 26% of those with food allergies responded by day 21. However, the vast majority responded within a 12 week time frame. Therefore, it is very important to keep the pet on the limited diet for the entire 12 weeks. If there is no change in symptoms but a food allergy is still strongly suspected, then another food trial using a different novel food source could be tried.
*DURING A FOOD TRIAL, ONLY THE RECOMMENDED DIET MUST BE FED*
*DO NOT GIVE*
Other food trial hints:
A large portion of allergies are environmental allergies – most of these are the inhalant type and are seasonal, with symptoms present only at certain times of the year. Many of these dogs suffer from intense itching, usually only seasonally initially, but symptoms can turn into a year round problem.
Allergy testing should be considered for any animal that is suffering from allergies that occur for more than four months out of the year, or do not respond to initial treatment. If allergy testing is recommended, consult with your veterinarian or a board certified Veterinary Dermatologist.
A definitive diagnosis of an allergy and determination of exactly what the animal is allergic to can be made by consulting with your veterinarian for allergy testing. There are two basic types of allergy testing –
Blood Testing – There are two types of blood tests used, the RAST and ELISA tests. In either one, a blood sample is drawn from the suspected atopic dog and screened for a reaction to a broad range of allergens including pollens, dust, grass, and molds common to your geographical area. Though this test can be used, because it was initially developed for humans, the antibodies that they test for are different in dogs and cats than in people. The result is that there are a lot of false positives, and the test could indicate that your pet is allergic to things when he is really not. For this reason, veterinary dermatologists recommend intradermal skin testing.
Intradermal Skin Testing – This test is considered the “gold standard” of allergy testing for atopy. The animal is sedated, and an area on his side is shaved in a patch down to the skin. A grid is laid out and small injections are made, done in order so that if the dog shows a small raised reaction, the allergy causing antigen can be identified. A veterinary dermatologist specializes in these, and is the best person to read such tests. Before undergoing such testing, the pet needs to be off all medications, specifically steroids.
The blood test and intradermal skin test have some similarities:
Allergy testing is the best diagnostic tool and the best road to treatment for dogs that are suffering from moderate to severe allergies. With appropriate testing, the hyposensitization injections have had good results in desensitizing your pet and reducing environmental allergy symptoms in many dogs.
Veterinary dermatologist Dr. Gordon has found that with the appropriate desensitizing injections, one-third of treated patients improve to the point they are eventually able to discontinue all therapy.
There are many options for treating dogs with allergies. Until the cause of an allergy is pinpointed, it is difficult to come up with the appropriate treatment. In the mean time, management practices like conducting a food trial and minimizing exposure to potential allergens can help in reducing symptoms.
A dog with food allergies requires no ‘treatment’, per se, owners just need to make sure their pet’s food does not contain the problem causing ingredient. Unfortunately, it can be a long process to try and figure out what the offending ingredient is! A strict food trial is the best way to manage your pet’s food allergies.
Without appropriate allergy testing, it is nearly impossible to decipher what environmental component your pet is allergic to. You can try limiting your pet’s exposure to possible or known allergens by using avoidance.
Avoidance can be very useful in managing atopy. While it may be impossible to eliminate all of the offending allergens, many can be greatly reduced by managing their environment. Avoidance is rarely 100% effective when used by itself, but can greatly reduce allergy symptoms.
For cases where exposure to the allergen cannot be controlled, such as in the case of a seasonal allergy, a veterinarian can prescribe your pet the correct dosage of an anti-histamine to help alleviate symptoms. Anti-histamines help control the immune system’s over-zealous response to an allergy, which then alleviates the symptoms. Steroids are also often prescribed by veterinarians to help alleviate symptoms, but unfortunately they just mask the symptoms, not actually reduce the problem. They can also have serious side effects due to long term use, and should always be used under the supervision of a veterinarian. Secondary infection is also common in allergy affected dogs, due to the pet itching and biting at their skin. Antibiotic treatment is often required to heal the resulting skin infection. Since bacterial and yeast skin infections are common in dogs with allergies, it is important to treat these infections as well as the atopy. Consult with your veterinarian to find the appropriate medications for your allergy prone pet.
Over the Counter
Not many over the counter oral medications are available to reduce itchiness in pets. However, Omega-3 fatty acids have been shown to be very beneficial in the management of allergies in dogs and cats. Fatty acids have been recommended for years to improve overall skin and coat quality, and it is now known that they work in the skin to help reduce the amount and effects of histamine and other chemicals that are released in response to allergies. The amount of success varies – some pets show little to no improvement, most show moderate improvement, and some seem to respond with a complete cure. Most pets need to be on the omega-3 fatty acids daily for several weeks to months to notice significant improvement. Omega-3 fatty acids are considered very safe and have very few side effects. It is important to use a fatty acid supplement derived from fish body oil, as other types of fatty acids – like omega-6 fatty acids – can actually create an inflammatory response, making allergies worse.
The first step in topically managing a pet’s environmental allergies is to simply wash off the dog’s feet and underside after he comes in from the outside. This will remove any allergens he came in contact with.
Other topical therapy consists of shampoos, rinses, and topical anti-itch solutions. This type of management offers immediate but short-term relief. Many over the counter sprays contain ingredients such as topical anesthetics to lessen the severity of the itching, an antibiotic to prevent secondary infection, and a bittering agent to prevent constant chewing. It is often recommended to bathe atopic dogs every two weeks or so with a hypoallergenic or oatmeal shampoo. Weekly or even twice weekly baths may offer increased relief for some dogs.
Topical sprays or solutions containing steroids such as hydrocortisone may offer additional relief. They are most appropriate when treating localized itching, and as they are used in moderation and are not readily absorbed into the bloodstream, do not create the long-term side effects associated with oral or injectable steroids. Consult with your veterinarian for treatment with any steroid containing products.
Dealing With Allergies
Trying to pinpoint the source of your pet’s allergies can be a time-consuming and frustrating experience. Using a combination of diagnostic tools, managing a food trial, and utilizing various treatment options, you can go a long way to helping your dog live a more comfortable life.
Still need help?
PetPeople is greatful for the guidance and support of Dr. John Gordon, DVM, Dip. ACVD.
Dr. John Gordon, DVM, Dip. ACVD
Board certified veterinary dermatologist
Medical & Cancer Center for Pets
300 E. Wilson Bridge Rd.
Worthington, OH 43085
Phone: (614) 846-5800
Fax: (614) 846-5803
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