Tips for Referring a Pruritic Dog or Cat

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Allergic dogs and cats can be among the most challenging patients that veterinarians treat, as allergy is typically a lifelong disease that requires ongoing treatment to maintain the patients’ comfort and to reduce and manage pruritic flares. Additionally, there is no “silver bullet” for allergy, and most patients require a multimodal approach for the greatest chance of success.

Veterinary dermatologists are a valuable referral resource to manage these cases, and primary care veterinarians are encouraged to discuss referral to a veterinary dermatologist for any chronically pruritic animal. Dermatology cases can be complicated, but there are a few helpful tips to keep in mind to maximize to maximize the benefits of a successful referral appointment.

• Ensure that regular flea and tick prevention is administered. Ideally, an isoxazoline product would be used, as these have the broadest reach in treating and preventing external parasites. Owners may not perceive the importance of this. It is important to remind owners that parasites cannot always be seen with the naked eye. Sarcoptic mites also are not always found on skin scraping, even in infested animals. Parasite control responsive itch is very common. In one large scale study of 502 pruritic cats presented for dermatology referral, flea control responsive hypersensitivity disorder was the most common cause of pruritus.¹ Additionally, fleas and ticks can transmit diseases which are harmful to both animals and humans. It is well known that ticks can transmit a variety of infectious diseases, but fleas are also problematic, as they can transmit murine typhus, Bartonella, and plague to humans. Preventing these diseases is always preferable to treating active infection/infestation.

• For patients with recurrent pyoderma, it is helpful to determine whether the animal is pruritic in the absence of infection. If pruritus resolves with resolution of infection, then other causes of recurrent pyoderma should be considered, such as endocrine disease. Allergic animals should be pruritic in the absence of infection. Additionally, if infection persists despite antibiotics, be sure to perform culture and susceptibility testing to determine if a resistant infection is present. If an animal has skin infection and is being referred to a dermatologist, the ideal time to refer is near the end of a four-week antibiotic course. Referral too early into an animal’s antibiotic treatment can make interpretation of the skin lesions challenging, as there is usually still evidence of active infection, and it can be difficult to determine how much the animal is improving.

• Try not to refer patients that are actively receiving steroids for management of pruritus unless no other symptomatic therapies are effective. Steroids decrease inflammation and can make it more challenging to diagnose pets with skin infection. Steroids also interfere with intradermal allergy testing, and a two-week withdrawal period of oral steroids is recommended prior to testing.² Injectable long-acting steroids require longer withdrawal periods. If steroids are being used for other purposes such as the management of an auto-immune disease, then they should be continued.

• Determine if food allergy is a possibility and perform a hypoallergenic diet trial to rule out food allergy prior to referral. If an animal has only seasonal pruritus, food allergy is unlikely, and a diet trial would not be needed. Diet trials should be done in any animal with year-round pruritus. It is important to use a prescription hypoallergenic diet (Table 1) for this purpose, as over the counter novel protein diets are often contaminated with proteins that are not explicitly on the label.^3,4

TABLE 1: Therapeutic Derm Diet Options for Dogs*

TABLE 2: Therapeutic Derm Diet Options for Cats**

Hypoallergenic diets come in two main varieties, hydrolyzed protein diets and novel protein diets. Either are acceptable to use for elimination diet trials. If a novel protein diet is prescribed, it is important to take a dietary history to make sure that the protein is a truly novel one. It is also important to address the other items a dog ingests in addition to their main diet, as clients may not realize these items are not allowed. Items to avoid during the diet trial include, but are not limited to the following: table scraps, treats, flavored medications, raw-hides, bully sticks and other animal-based chews. In all cases the item should be assumed to be contraindicated during a diet trial unless total reassurance can be obtained that the item is actually hypoallergenic.

A diet trial can be a challenge for many owners. In some households, for example those with very small children, a proper diet trial may not be practical. In cases where a diet trial is not possible, it may be better not to force the client to do a trial which is not likely to be successful, as this will only frustrate all parties. While skipping the diet trial is not optimal, it may be indicated when the elimination trial cannot be done correctly. In these cases, the animal can be referred to a veterinary dermatologist without having the diet trial performed.

This short list is not necessarily comprehensive, and different veterinary dermatologists will have different preferences. Additionally, it is not always practical to follow every one of these recommendations. Primary care veterinarians are encouraged to develop relationships with their local specialists to determine if they have different preferences than those listed here. Good communication between specialists and primary care veterinarians is paramount to the health of their patients. Setting up a referral case for success can greatly improve the efficiency of the initial appointment and can make a tremendous impact on client satisfaction!