Allergies

Dermatology update

By: Dr. Sheri Sime 

A number of tests may be useful to efficiently diagnosis a skin disorder and decide the appropriate course of treatment.  

Cytology samples are taken using swabs, slides or tape.  It allows us to examine and identify bacterial , yeast, and  inflammatory cells in the ears or on a pet's skin.  This economical and quick test helps us with a diagnosis and  it may be repeated in a patient on future visits to help us monitor response to treatment or recognize a concurrent illness. This can include allergies, concurrent illness, immunosuppression or thyroid problems.   

Bacterial cultures are not routinely carried out with uncomplicated skin infections, this is occasionally recommended to help us to identify both the bacterial present, as well as what is the appropriate treatment.  Methicillin resistant staphylococci infections  has now also been identified.  It a pet has not responded to treatment as expected, has a recurrence of symptoms, or has a potentially zoonotic infection, cultures should be carried out.  

Skin scrapings and biopsies may also be occassionally carried out helping us to identify some parasites or the latter when skin disease is severe or un responsive to treatment.  Immune mediated diseases, congenital skin diseases and tumors may be manifested and identified through biopsies. 

Goals of Allergic dermatitis management:

1. reduce inflammation and itchiness

2. treat secondary infections; yeast and bacteria

3. alter a pets over reactive immune system

4. increase the skin barrier

5. reduce allergen exposure 



Allergies

Recurrent skin problems, ear inflammation and secondary infections are common manifestations of allergies in our pets.  Like people, they often have not just one, but a number of allergies and it is often a substance that cannot be eliminated from their environment.  Although we cannot "cure" allergies, our aim is to manage them to maintain their comfort.  This is often accomplished by combining different treatments to accomplish comfort, while minimizing potential drug side effects.   Again, not all itchy pets have fleas!!  If your pet is itchy they may have a food  or air borne allergy. Allergies can be inherited; an affected pet should not be bred. 

Inhalant Allergies

Airborne allergens include; pollen, dust mites and molds.  Pets affected by inhalant allergies may present with chewing, scratching, licking and biting of their feet, flanks, groin and armpits areas.  These allergens lead to inflammation as a result of skin contact.  Although we cannot eliminate most of these substances from their environment, we can limit their exposure.  The most common environmental allergy recognized in pets is actually dust house mites.  They feed off skin scales so it is important to regularly wash bedding (at over 55C), and ideally keep pets off upholstered furniture.  Using an air conditioner, keeping your windows closed, installing an air purifier, removing rugs can also help.  Regular bathing of pets, and vacuuming of you house are also helpful.  Plants should be removed if your pet has a mold allergy.  If not removed, cover the soil with activated charcoal bits (aquarium supplies) to prevent mold growth. Using dehumidifiers to maintain relative humidity between 30-50% can also help.

Bathing using cool water and a veterinary antibacterial shampoo is extremely helpful.  The cool water acts as an anti-inflammatory, and rinses off air borne allergy.  Leaving the shampoo on for 10-15 minutes allows for an antibacterial effect both preventing and controlling secondary bacterial infections.  


Food Allergies

An animal does not have to be exposed to a new food to suddenly develop allergies; they may develop symptoms from products that they have been exposed to for years. Symptoms of food allergies include biting, licking and chewing of the feet, face or ears. It is often difficult or impossible to differentiate these allergies from air borne allergies, and most pets have a combination of both. Recurrent ear infections are often the ONLY manifestation of underlying allergies.  Some animals with food hypersensitivities will also present with gastrointestinal symptoms including diarrhea, vomiting, and flatulence.  In extreme cases they may experience seizures. Pets with a food allergy may be below the threshold for showing symptoms, but when another antigen is present, the animal becomes clinical (outward signs).  Pets with seasonal allergies may have a food allergy component and benefit from a prescription hypoallergenic diets.  We do not recommend over the counter products for pets with allergies, as they often contain ingredients not listed on the label. 

Most of the commercially available diets have similar ingredients, so it is not uncommon to have them react to more than one diet. Common food allergies for dogs include chicken, beef, pork, milk products, eggs, soy, wheat, and preservatives.   In cats, common allergies include beef, milk products and fish. As more and more commercially available diets have turned to alternative protein sources, what was once considered hypoallergenic or a novel protein source is now commonly found in many diets and will not help a pet with a food allergy.  For instance Lamb and fish are no longer novel proteins for many pets.  Commercially available lamb and rice or "hypoallergenic" diets can contain chicken, soy, and wheat, etc.  A study of over the counter 'soy free' products found that actually about 75% of them had soy!  

If a pet has eaten an ingredient to which they react, the response can be seen for upwards of 3 months.  I have had a patient with recurrent ear infections develop approximately 48 hours after the consumption of facial tissue. If a pet is placed on a prescription or homemade "hypoallergenic" diet, it is critical that nothing else is fed to them during the initial 3 month trial period.  This includes people food, treats, and some oral heartworm medications (use an alternative).  Nothing should be fed with medications given. Novel ingredient prescription hypoallergenic diets, and hydrolyzed protein prescription diets are now available. The latter types of diets are often used during a food trial to determine if a pet has a food allergy component to their symptoms. Approximately 80% of pets with food allergies will respond to prescription hypoallergenic diets.  These diets also contain anti-inflammatory elements.  As not all pets respond, up to 3 different diets would be utilized for diagnostic purposes. 

A homemade diet which contains novel proteins can be fed to those that do not respond to any of the commercially available hypoallergenic diets.  These diets are not meant for long-term feeding as they are not nutritionally complete.  These trials start with a starch (potatoes or rice) and a novel protein source (rabbit, deer, kangaroo, moose) in a ratio of 2:1.  The ingredients are boiled and fed during a short term trial. Then individual ingredients are to be reintroduced on a weekly basis.  When symptoms recur we can likely identified an allergy inducing ingredient. We then try and find a diet which does not contain these ingredients. Note blood and skin testing for food allergies is not reliable. 

Flea Allergies 

Dogs which have an area just above their tail base with alopecia (hair loss) and pruritus (itching) are often pets affected with flea allergies.  The symptoms occur long after the flea has left the area. When a flea injects saliva into the skin to which the patient reacts.  This reaction will carry on for up to a week. Flea prevention is the key. 

Diagnosis

Skin allergy testing involves shaving a pet and injecting various antigens and measuring the immune system's response.  The identified substances creating an excessive immune response are then formulated into a series of injections to be administered over six to eight months.  The aim is to try to fatigue the immune response to these substances.   Dermatologists report about a 75% response rate to immunotherapy.  When skin testing is not possible, blood testing may be designed to identify allergens, however the accuracy of these results is questionable.  Skin allergy testing requires a referral to a dermatologist.  Prior to the appointment with the veterinary dermatologist, it is important that all steroid-containing topical skin, oral, eye and ear products are stopped.  These can influence the skin reaction results.

Management options

Pets should be under the direct supervision of a veterinarian.  They will provide individualized recommendations on what would be the safest and most effective treatments for your pet.

Topical Products

Topical sprays come with anti inflammatories, low levels of corticosteroids  or antibiotics(Cortavance, Topagen) have been used for a short term on localized spots.  Corticosteroids used on the skin or within inflamed ears are systemically absorbed over time, and can lead to potential side effects. 

Bathing

Cool water bathing with medicated shampoos offer temporary relief. The shampoos will help to relieve itchiness. Some are sulphur/salicylic based (Sebolux), chlorhexidine (Pro Hex), or oatmeal based (Epi-Soothe).  Skin may then need to be moisturized with cream rinses or sprays (humilac, epi-soothe).  Please note a hypoallergenic shampoo is indicated for skin sensitive pets, not for those pets with an allergy. 

Antihistamines

Approximately 33% of dogs will have a reduction in itching.  If one antihistamine does not offer any relief, another should be tried.  Sedation is a common side effect.  My preference is hydroxyzine for dogs, chlorpheniramine in cats.

Prescription Omega 3, 6 Fatty Acids

Fatty acids can improve symptoms in patients and have few side effects.  Their anti-inflammatory benefits not only help skin inflammation, but arthritis too as well as helping senior pets and senility. They alone are not expected to control an allergy, but are often used in combination with other therapies. Products such as  Welactin help about 20% of patients. These products differ from the commercially available fatty acids to improve the coat quality.  

Corticosteroids 

These can offer a pet immediate relief from the itching, but can have side effects throughout the body when used longterm.  When used, we try and combine them with other treatment modalities, and find the lowest possible alternate day dosing that will maintain a pet's comfort. Common side effects include increased urination and appetite, and some pets will experience behavioral changes.  Long term use of corticosteroids can lead to the development of diabetes, immunosuppression, or Cushings disease. Safer products, with a lower dose of corticosteroids combined with antihistamines (Vanectyl-P) are commonly used.

Monoclonal antibody 

Cytopoint is an injectable monoclonal antibody that targets and inhibits the cytokine IL-31 involved mainly with pruritis.  Cytopoint is a rapid, safe and effective means of controlling air borne allergies in some pets.  There is no minimal age in which it can be utilized, and has no contraindications for its use, including tumors.  It can be used in combination with other modalities of treatment, however it does not reduce inflammation, so in an already inflamed pet, its use needs to be combined with other treatments.  Its duration of action can be between 4-8 weeks.  Cost in a larger dog remains one of the disadvantages of its use.




Immune Modulators 

Cyclosporin (Atopica) has offered pets comfort when other regimes have not.  It is labeled for dogs over 6 months of age or older.   It is a safer longterm treatment for a pet than long term steroids.    Pets respond slower to this medication than some others,  and for upwards of 3 weeks its treatment may need to be combined with other drugs including glucocorticoids initially.  Side effects can include vomiting and diarrhea when initially started, and possibly skin growths and gum hyperplasia (overgrowth) when used long term.  They are contra-indicated in patients with tumors. This is an immunosuppressant that works on cell-mediated immune responses.  

Apoquel is an oral medication used for the management of puritus (itch) in dogs over 12 months of age.  It affects various cytokines at the receptor level responsible for both inflammation and pruritis.  It has a rapid response and is tolerated by most dogs, even long term.  This medication is contra indicated when tumors or severe infections are present.  

Periodic bloodwork and urine is recommended for in pets utilizing some of these modalities of treatment. 


T-shirts, E-collars and Booties

Putting a t-shirt or onesie, e-collar or booties on your pet may help prevent them from licking, chewing and scratching at themselves.  This will help prevent secondary infections.  Also t-shirts, onesies or booties can help with protect them from outdoor allergens when they are on walks or outdoors.

Increasing the skin barrier

The entry of environmental allergies is thought to be through impaired skin.  Inflammation and infection can hence play a role.  Essential fatty acids, and products that help to improve the skin barrier are included in veterinary specific atopic diets and in topical therapies including the douxo line of products. 

Allergies remain one of the most costly and frustrating diseases for a pet and their owners.  We are unable to cure allergies, but with the proper steps taken we can manage them so your pet can enjoy a high quality of life.