The topic of allergies is very complicated, with multifaceted conditions difficult to diagnose, and are a major frustration for the client and veterinary staff. The major symptom in all cases is pruritus (itchy) skin. The patient exhibits scratching, rubbing, licking, and/or chewing. Additional symptoms such as: inflammation, self-trauma, hair loss, lesions and/or skin changes, may also be present. The areas affected could include the muzzle, ears, flanks, groin, forelegs, or feet.
The initial focus of any itchy patient is to determine the underlying causes of the pruritus. It is only after all other causes have been excluded that the veterinarian can determine that the condition is due to an allergic reaction. Other causes of skin infection and itchy skin can include:
parasites - mange mites, lice, fleas, chiggers
bacterial infections
fungal infections
endocrine disorders
behavioural - feline psychogenic alopecia, stress.
The first step in the diagnosis is to obtain a detailed history of the animal. The history should include previous health conditions, eating habits, dietary history of all things ingested (food, treats, human food, medications, supplements), activity level, and areas where the activities take place as well as noting other pets in the household.
Secondly, a thorough physical exam is required. During the course of this exam, the veterinarian may choose to run certain tests based on the findings during the physical exam. The tests could include skin scrapings, bacterial and/or fungal cultures, and blood work. If another disease process is suspected, further testing and follow up would be appropriate. If an underlying cause is found then the pet will be treated appropriately.
Flea Allergies - In cases of flea allergy, the patient is reactive to saliva of the flea. Pruritus is localized to the area of the flea bite(s) and generally ear disease is not present. Treatment consists of treating the patient and its environment for fleas. All pets in contact with the patient must undergo treatment to eradicate the burden of fleas in its environment.
Atopic Dermatitis - This is inflammation of the skin cause by sensitivity to allergens in the environment. This dermatitis may have a seasonal or genetic component (breed may be genetically predisposed to sensitivities). Atopic dermatitis presents itself with pruritus, recurrent bacterial (ie. staphylococcal), or yeast dermatitis (ie. malassezia), and in dogs specifically, ear infections (otitis externa). Otitis externa is rarely seen in cats. In some cases, cats may exhibit asthma-like respiratory tract disease. Dust mites, pollens, mould spores, danders, and insects are the most common sensitivities. Treatment may consist of one or more of the following: anti-inflammatory therapy, antimicrobial therapy, allergen avoidance, and/or Allergen Specific Immunotherapy (ASIT). Anti-inflammatory and/or antimicrobial therapy can be prescribed to keep the animal comfortable during episodes or to control flare-ups. An attempt should be made to determine the triggering allergen. If there is no known underlying cause and the dermatitis is year round, a food trial should be considered. Allergy testing should only be carried out after all other causes have been ruled out. Allergy testing is best performed when the allergy load is highest and prior to any medication therapy. Once the allergen(s) has been determined, ASIT can be administered. This is a process of administering gradually increasing quantities of an allergen extract in order to desensitize the patient to the offending allergen(s). One-third of the patients given ASIT have an excellent response, while 1/3 have a good response, and 1/3 have a poor, or no response, to the therapy.
Food Allergy - This is a non-seasonal inflammation of the skin caused by sensitivity to allergens in food. Adverse food reactions can develop over time. The patient becomes sensitive to a specific protein, or food additive, in the diet. The pruritus is distributed similar to that of atopic dermatitis and these two diseases are clinically indistinguishable if symptoms are non-seasonal. Once all other underlying causes for pruritis are ruled out, and anti-bacterial and antimircrobial therapy has cleared the inflammation, the pet is put on a food trial. A diet with a novel protein is selected and must be fed for 6 to 8 weeks. there must be strict adherence to the diet - no other foods, treats, supplements, etc. can be fed during the trial. The client is advised to keep a diary to record the food fed and symptoms present. If truly a food allergy, improvement may be seen as early as two weeks into the trial. If at the end of the trial, there is significant improvement, the patient is reintroduced to the previous diet. Re-occurrence of symptoms is definitive of food allergy. If there is only a partial improvement, a second trial with another novel protein diet may be warranted. If no improvement with the diet trial, then a food allergy is ruled out.
Allergic conditions are life-long. There is no cure for allergic conditions. However, your veterinarian can offer medication regimes and other strategies to assist in managing the condition(s). Most regimes start with a medication(s) to decrease the allergic reaction or itch. However, it must be noted that some of the new medications on the market are very expensive and beyond the reach of some pocket books, particularly for very large dogs needing treatment.
These medications include:
Cytopoint (licensed for dogs only) is a synthetic antibody that neutralizes a specific type of cell involved in allergy. This drug is an injectable administrated at 4-week intervals. $$$$.
Prednisolone and Prednisone are anti-inflammatory steroids which inhibit the process of inflammation. This medication is available in pill or liquid form to be administered daily. $
Atopica is also an anti-inflammatory that inhibits the different cell types involved in allergy. It comes in capsule or liquid form for daily administration. $$$
Apoquel (licensed for dogs only) blocks neural pathways that cause the sensation of itch, and is a tablet administered daily. $$
Allergen Specific Immunotherapy requires the pet to undergo allergy testing. Based on the test results, a solution containing small amounts of selected allergens is created. This solution is injected into the pet every few weeks, then every month. The intent is to desensitize the pet to the allergens causing the allergic reaction. $$$$
In addition, the anti-allergy medications, antibiotics and/or anti-fungal medication may be dispensed to decrease inflammation and manage secondary infections. Antihistamines and/or specific shampoos may be recommended to help ease the pruritis. Devices such as buster collars, t-shirts, and socks or booties, may be recommended to control self-inflicted trauma, especially during times of severe outbreak.
The allergic pet requires constant monitoring. Any change in the skin condition needs to be reported to your veterinarian and prompt response is needed to avoid severe outbreaks.