Allergies in dogs most often present with chronic or recurrent itching (pruritis) due to an over-reactivity or hypersensitivity of the immune system to a particular substance called an allergen. The itching most often manifests in the paws (feet), face, and ears; but, these are by no means the only areas in which itching is seen. Allergic reactions in dogs can present not only as skin reactions from allergen contact, but also skin and respiratory symptoms from inhaled allergens and digestive symptoms from food allergies. Owners of itchy dogs often suspect fleas; however, this is not nearly so often the case, especially with all of the effective products on the market for flea control.
Causes of Allergies in Dogs
- Flea Allergy Dermatitis (FAD)
- Environmental Contact or Inhalant Allergy (Atopy)
- Food Allergies
- Bacterial (Staphylococcus) Hypersensitivity
The development and progression of allergies in dogs is determined by the accumulation of environmental allergen exposure over time, heredity, secondary bacterial infections, self-induced trauma, altered immune response and impaired skin barrier function. Most dogs begin to show their allergic signs between 1 and 3 years of age.
Flea Allergy Dermatitis (FAD) in Dogs
The most common dermatologic (skin) disease of dogs is flea allergy dermatitis or flea bite hypersensitivity as a result of fleas. When feeding, fleas inject saliva that contains allergy producing substances.
Environmental Contact or Inhalant Allergy in Dogs
- Atopy (environmental allergies) results from exposure to everyday allergens through skin contact or inhalation. Atopy in dogs is also called atopic (atopy) dermatitis or canine allergic inhalant dermatitis:
- Atopic Dermatitis occurs when allergens that contact the skin cause an allergic reaction in the body, most commonly the skin
- Allergic Inhalant Dermatitis occurs when allergens that are inhaled cause an allergic reaction in the body, most commonly the skin
- Atopy is the most common cause of itchy ears and ear infections dogs, whether they are inhalant/environmental or food related.
- The main places dogs with allergies seem to itch is the feet, face, and ears
- The second most common is the tail head, trunk, limbs, ears, axillary ("armpit"), inguinal ("groin") and perineal (genital/anal) areas.
Food Allergies in Dogs
Food allergies are most often due to a sensitivity to one of the main ingredients in their food, usually a protein or carbohydrate. Food allergy symptoms may include chronic or intermittent gastrointestinal (GI) disturbances like vomiting and diarrhea. However, food allergies may also have skin manifestations that include hives (itchy, red, bumpy rashes), inflamed skin, bald spots and recurrent ear infections.
Bacterial (Staphylococcus) Hypersensitivity in Dogs
Also called Staphylococcal pyoderma or Staph. pyoderma. This is an allergy to the normal bacterial flora (Staphylococcus) of the skin. This bacterial hypersensitivity is an over-reactivity of the dog’s immune system to the normal skin bacteria. This condition in dogs occurs more often when other conditions are present like flea allergy, hypothyroidism, and/or inhalant allergy. Bacterial hypersensitivity is diagnosed through bacterial culture looking for staphylococcus and a skin biopsy demonstrating unique changes in the blood vessels of the skin.
Dog Allergies – Type I Hypersensitivity
Dog allergies are a result of a hypersensitive immune system, one which overreacts to a stimulus. The most common type of allergic reaction people see in their dogs (and in themselves) is a Type I Hypersensitivity (there are 4 Types, but for the scope of this writing, only Type I will be addressed). Learn more about dog allergies due to hypersensitive immune response.
Pruritic (Itch) Threshold
The idea of the pruritic (itch) threshold is that there is for every animal (or person) a level or amount of allergens (allergy inducing particles) that must be present before symptoms (itching, etc.) will occur. Learn more about the pruritic (itch) threshold on our webpage discussing Allergy Shots (Immunotherapy) for Dogs.
Impaired Skin Barrier Function
The impaired skin barrier function is another component of skin allergy and is related to the skin, a physical barrier protecting your dog. Some allergens cause symptoms by physically invading the skin between the cells. Learn more about impaired skin barrier function in dogs on our allergy shots for dogs page.
Symptoms of Allergies in Dogs
Dogs with atopy will usually lick, rub, lick, scratch and bite areas affected like their ears, feet, armpit and groin at their feet, flanks, ears, armpits, or groin. This results in hair loss and red skin and swelling.
- Itchy ears and recurrent ear infections
- Increased scratching
- Itchy, runny eyes
- Snoring caused both throat inflammation and swelling
- Itchy, red, moist or scabbed skin
- Increased scratching
- Itchy, runny eyes
- Paw chewing/swollen paws
- Constant licking
- Itchy back or base of tail (most commonly flea allergy)
Allergic dogs may also suffer from secondary bacterial or yeast skin infections, which may cause hair loss, scabs or crusts on the skin.
Most allergens in dogs are proteins of insect, plant or animals. Happens are small chemical molecules the also cause allergies. These are the most common allergens in dogs:
- Insect proteins such as flea saliva, a few flea bites can trigger intense itchiness for two to three weeks!
- Pollen from tree, grass and weeds
- Mold spores
- Dust and house dust mites
- Dander, shed skin cells
- Dust mites
- Cigarette smoke
- Food ingredients (e.g. beef, chicken, pork, corn, wheat or soy)
- Prescription drugs
- Insecticidal shampoo
- Rubber and plastic materials
- Cleaning products
Diagnosing Allergies in Dogs
Our veterinarians will take a thorough clinical history to determine the reasons for your dog’s skin allergies. Once they have a working differential diagnosis they will assist you in prioritizing the necessary steps for treatment. Some of the criteria for further testing include:
- Allergy symptoms beginning around 6 months of age or later
- Clinical symptoms that occur seasonally
- Hereditary nature of allergies in certain dog breeds
- A positive clinical response to antihistamine/steroid treatment.
Treatment for Allergies in Dogs
Allergen Avoidance Therapy
This is the most effective but often least possible treatment choice. If we are able to remove the offending agent from the environment or diet, then there is no stimulation and therefore no reaction. This is most easily done with food allergies by using elimination diets and/or novel protein diets. An elimination diet basically means feeding a diet from which all offending food sources have been eliminated. Novel protein diets simply mean feeding a diet in which there is a novel (new or never seen by the body before) protein source. Quite often the two diets used are one in the same.
The hard part of the food component is that it can take 2-6 months of feeding a strict diet before the body no longer shows reaction to the allergens from the old food. Allergy testing by blood sample may help at least rule out some of the more reactive foods to help streamline the diet selection.
Allergy Testing and Immunotherapy (Immune-Modulating Allergy Shots)
Allergy testing is the best way to find the source of some allergens to see if there is something that can be removed from the environment or diet, or if there is a specific serum that can be made for the pet in question so that they are not nearly so reactive to that allergen. Once tested, a serum or "vaccine" can be manufactured that is specific for the offending allergens for a given patient. The idea behind this is to inject small concentrations (Immune-Modulating allergy shots) of the allergens to teach the body to make IgG instead of IgE. This Immunotherapy (Hyposensitization) can take a few months to a year before a patient responds favorably to the injections, and there are cases in which some patients never respond properly. Many people are stopped by the cost of the testing up front, but if they were to add up all financial costs of the exams, tests, pills, injections, and topical medications that they end up buying to treat the chronic skin and ear issues; plus the physical cost to their pets (and emotional costs to themselves)from the chronic inflammation, irritation, discomfort, and infections from the allergies, then testing will almost always pay for itself in the long run. Please remember that allergies also can change with age, so the results of one test may not be the same years later as new allergies can develop with time. If a patient that has been doing well on injections for a period of time develops symptoms again, it is often recommended to retest to be sure a new allergy has not developed. If one has, then the serum for the injections needs to be changed.
Oral Medications for Treating Dog Allergies
Antihistamines work well in very few dogs (maybe 15%). They actually fail more often than they work. They do not stop the allergic reaction; rather they work by stopping or slowing the release of the histamines from the mast cells. They are a symptomatic treatment. They usually have very low side effects and can be used on an as needed basis. They tend to be relatively inexpensive. Even those who report some level of improvement with antihistamines may find that they no longer work the next season. Also, there is no way to tell if the antihistamines "working" coincided with some pollen source leaving the environment thus lowering that pet's exposure level making them fall beneath their threshold. This means they would have improved without the anti-histamines anyway.
Steroids work very well, but they do not necessarily stop the allergy, but they do decrease the immune system response and the effects of the inflammatory chemicals in the body. They also tend to be relatively inexpensive. Chronic use however can be detrimental to your pet's health. They have many potential side effects including but not limited to: increased thirst, increased urination, increased appetite, weight gain, lowered wound healing, lowered immune response, behavioral changes. They are usually best used in short courses to get immediate results while looking to other long term therapy choices.
Immune regulating agents such as cyclosporine or Atopica work by lowering the immune system response and therefore lowering the symptoms. They have fewer side effects than steroids, but tend to be more expensive.
Newer medications such as Apoquel (a synthetic Janus Kinase (JAK) inhibitor) are showing great promise. They are not antihistamines or steroids. They inhibit the function of a variety of pruritogenic (itch-causing) chemicals in the body called cytokines and pro-inflammatory (inflammation causing) cytokines, as well as cytokines involved in allergy that are dependent on JAK1 or JAK3 enzyme activity. They, like most medications, are not devoid of their share of side effects and precautions, but many pets are experiencing relief they have not felt in years from this breakthrough. You veterinarian can best educate you on whether your dog is a good candidate for this medication.
Omega -3 fatty acids are products found in certain foods and in supplements that have no real side effects and can greatly reduce the inflammation in the skin caused by allergies. They can be used in conjunction with any of the other therapies.
Topical Therapy with Medicated Shampoos and Conditioners
Sometimes pets respond well to topical therapies like sprays and shampoos. The sprays most often have a steroid or antihistamine base, with some having a mild topical anesthetic added. Some have antimicrobial activity as well. These are usually temporary treatments. The shampoos may have benefit from actually physically cleansing the allergens off the skin; from applying anti-inflammatory products; or from treating secondary bacterial and yeast infections.
If you suspect that your dog has allergies, please come in and see if we can help you and your pet get some relief. Please call 972-731-0001 to schedule an appointment or complete an Online Appointment Request to meet with our veterinarians at the Plantation Pet Health Center in Frisco.