Bringing Allergy Testing to the Standard Examination

Shannon Palermo, VMD, University of Pennsylvania

Dermatology|CE - RACE Approved

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Bringing Allergy Testing to the Standard Examination

Sponsored by Spectrum 

Introduction

Itchy pets are one of the most common reasons for examination room visits; however, clinical signs of allergies may be mild at the onset. By incorporating allergy testing into standard examination visits, appropriate treatment can be initiated sooner to provide faster relief to pets (and owners). Allergy testing can also help eliminate other possible causes of skin disease such as endocrinopathies, immune-mediated disease, and neoplasia. There is no cure for allergic disease, but proper diagnosis is the first step toward successful long-term management.

When Allergy Testing Should Be Recommended

Chronic, Intermittent GI Signs

The prevalence of allergy-related GI conditions is not known, but estimates range from 10% to 23%.1 Exposure to allergens results in an IgE-mediated antibody response, and the culmination of these responses results in the clinical manifestation of allergy signs. Serum IgE tests such as Spectrum’s SPOT test will detect levels of allergen-specific IgE for each food type. Approximately 90% of patients tested for environmental and food allergies and subsequently hyposensitized show significant improvement in clinical signs, according to a survey of veterinarians.2

Recurrent Ear Infections

Many dogs with food allergies or atopy have skin lesions associated with the ears, which can lead to recurrent otitis externa. Allergies account for approximately 5%-10% of all skin disorders and 31% of non-seasonal canine dermatitis cases.3 Without removing the inciting cause or predisposing factor, ear infections are likely to continue to recur and can lead to fibrosis and narrowing of the ear canal. Surgical correction is ultimately necessary in many cases.

Excessive Grooming, Pruritus

Excessive itching and scratching not only places pets at risk for secondary infections but also can (literally) keep owners up at night. Itchy pets are at risk for developing secondary infections, which can delay time to clinical improvement and can create a cycle of inflammation and perpetuation of skin disease. Specific allergy testing for these patients can lead to diagnosis and allow the initiation of specific treatment to break the itch cycle.

Scooting & Anal Sac Disease

Skin inflammation and allergic skin disease can predispose pets to developing anal gland problems. This can manifest as recurrent scooting, licking, or biting at the region. Food intolerance is also a common cause of anal sac disease. Problems result secondary to glandular hypersecretion and perianal inflammation. If left untreated, impaction, anal sacculitis, and abscesses may occur.

Red or Swollen Eyes, Sneezing

Seasonal allergies can result in both ocular and nasal signs. These signs may be subtle, but they can last the entirety of the allergy season and cause discomfort and irritation to pets that suffer from seasonal allergies.

Respiratory Signs

Patients that suffer from coughing and nasal congestion, especially seasonally, are great candidates for allergy testing. Although these clinical signs are also found with primary respiratory diseases, missing a diagnosis of allergies can result in overmedicating and masking clinical signs without appropriately providing treatment and relief to pets suffering from seasonal allergies.5

Early diagnosis is key to treating allergic conditions. Medicating clinical signs without definitive diagnosis may only mask the underlying problem at hand and lead to long-term treatment failure and further complications. Once on treatment, these patients should continue immunotherapy year-round to ensure proper management and maximum comfort.

The Importance of a Thorough History

The first step in treating an allergic patient is obtaining a thorough history. The most common allergies in pets are flea allergy, food allergy, and atopy. Inquiring about environmental triggers, seasonality, current diet, and recent dietary changes can provide a great deal of insight regarding the cause of a pet’s clinical signs and can ultimately help with diagnosis. For example, a pet with clinical signs that are seasonal is unlikely to have a food allergy. Clients should be instructed to keep a log or diary of clinical signs, which can help identify allergy triggers or patterns of seasonality. A good history alone can narrow the differentials and help guide the most appropriate next diagnostic step.

Dietary Trials

Food allergies account for approximately 9% to 36% of allergies seen in dogs and approximately 40% of allergies seen in cats.3,4 They represent the third most common allergy (after flea-bite allergy and atopy) in the pet population.6

The most common culprits are protein sources in the diet. A diet trial consists of feeding a novel diet—ideally for 12 weeks, but for a minimum of 8 weeks. There are 2 types of commercial diets available: novel protein diets and hydrolyzed protein diets. Novel protein diets contain unusual protein sources such as kangaroo, catfish, and venison. Hydrolyzed diets include common protein sources that have been broken down to short peptide chains; this theoretically makes them unrecognizable to the immune system. Home-cooked diets may also be used, but supplementation is required with long-term use.

During a dietary trial, it is crucial to avoid all other diets, treats, and flavored medications. Many owners find this challenging, but compliance is crucial. If a marked reduction in clinical signs occurs after 8 weeks, the pet is then challenged with the original diet. If clinical signs return following this challenge, food allergy is diagnosed.

Specific Allergy Testing

The most reliable way to definitively diagnose allergies in both dogs and cats is with specific allergy testing. Allergy testing can provide a diagnosis for an itchy pet and is the first step toward long-term management via allergen-specific therapy.

There are 2 types of allergy testing available that involve serum or skin testing. Blood tests evaluate for allergen-induced antibodies in the serum and include both radioallergosorbant (RAST) and ELISA tests. Neither test is affected by recent steroid administration or by cyclosporine or antihistamine use.7 The second category of allergy testing is intradermal skin testing, which does require weaning off of any suppression therapies prior to testing. Intradermal testing involves injecting test allergens under the patient’s skin and monitoring the injection sites for evidence of an allergic reaction. Both blood and intradermal tests evaluate specific allergens, which vary based on geographic location. Once a diagnosis is confirmed, specific treatment can be initiated to provide allergy relief.

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