Helpful hints for the successful treatment of canine atopy

2013-08-01
Alice M. Jeromin, RPh, DVM, DACVD

These practice pearls may help alleviate some of the itch of this irritating condition in your veterinary patients.

We're at the height of allergy season here in the Midwest after enduring an extremely high tree pollen and grass pollen season. Needless to say, people with atopy have been suffering along with our pets. Even if you're not allergic, the high pollen counts tend to act as an irritant, bothering both mucous membranes and the respiratory system.

The conventional means of controlling the clinical signs of canine atopy have been discussed in the past (see dvm360.com/dermatology). Here I want to offer some small pearls based on new evidence of the pathogenesis of atopy that may make your patients more comfortable.

Topical measures

Topicals such as shampoos, leave-on anti-itch conditioners and ceramide replacement products seem to have gained new importance based on the pathogenesis of atopy in dogs. New evidence shows that absorption of the allergen across the skin (percutaneous absorption) may be the primary mode of getting the allergic response started.1,2 It certainly explains why in dogs with atopy, the face, feet and perineal areas are most often involved (Photos 1 and 2).

Photo 1. Clinical signs of atopy can include alopecia and excoriation as seen in this young dog from rubbing its face. (PHOTOS COURTESY OF DR. ALICE JEROMIN)

Once sensitized, dendritic cells that "patrol" the body are presented with antigen, which starts the immune system going, switching to T-helper lymphocyte-2 production with consequent cytokines that create inflammation. Ceramide production/destruction, filaggrin, and other structural elements of the epidermis are compromised, resulting in destruction of the normal skin barrier.1,2 This results in more absorption of the allergen across the skin. Also, the normal resident bacteria of the skin tends to multiply and produces enzymes that further break down ceramide.1,2

Photo 2. A common sign of atopy in dogs is licking of the caudal carpus, as evidenced by the alopecia and the copper-colored staining of the adjacent fur from saliva.

After a while, chronic changes occur that are difficult to reverse and further perpetuate the condition. Frequent bathing helps to remove the allergen, which can prevent the whole process from starting. It also reduces bacterial colonization. Since frequent bathing can be helpful in most dogs, choose a shampoo that is mild without ingredients that may cause drying (dry skin enhances allergy absorption). A hypoallergenic shampoo followed by a topical low-potency, water-based hydrocortisone such as Resicort (Virbac Animal Health) as a leave-on rinse can help "put the fire out." Shampoos with phytosphingosines can be helpful in keeping the epidermal barrier in check.

Wiping off the feet, ventral abdomen, medial pinna and perineal areas (the nonhaired areas of the body) when dogs come in from outside will reduce the pollen load. Using just a damp cloth or antibacterial wipes such as Preva Medicated Wipes (Bayer Animal Health) or the bovine nisin wipes (Wipe Out Dairy Wipes—ImmuCell) is inexpensive and helpful. Clothing such as cotton t-shirts and onesies can act as a barrier to percutaneous absorption of allergens.

Topical skin lipid complexes containing ceramides, botanicals and fatty acids such as Allerderm Spot-on (Virbac Animal Health) and Dermoscent Essential 6 (Aventix) can help repair stratum corneum lipids.3 This can aid in restoring a normal skin barrier. The topicals are typically used once weekly but can be used more or less often depending on the patient's response.

Nutritional measures

There is evidence to show that the proper diet may help relieve clinical signs of atopy.4 Flaxseed oil and fish oil are both rich in omega-3 fatty acids. For flaxseed oil to have anti-inflammatory effects comparable to fish oil, it must be converted to eicosapentaenoic acid (EPA). Unfortunately, conversion in dogs is only about 10 percent, so fish oil is a better source of omega-3 fatty acids in dogs.

Diets rich in essential fatty acids (EFAs) may provide higher amounts of fatty acids than are available via capsules. The best time to start an atopic patient on a diet containing EFAs would be two to three months before its allergic season since it can take two months of EFA supplementation before results are seen. In a study of 50 atopic dogs fed one of four diets over an eight-week period, the dogs fed a fish-based diet had a much lower pruritus score.4

It is now known that reactions to food ingredients can mirror the clinical signs of atopy. There appears to be cross reactivity between foods and inhalants, with grasses cross-reacting with grains as an example. It may be a good idea to start a therapeutic hypoallergenic diet in atopic dogs one to two months before their affected season. There are currently no over-the-counter hypoallergenic diets, despite some food manufacturers "alluding" to such. A study examining four over-the-counter foods labeled as venison-only contained soy, poultry and/or beef protein in the formulation, and these were not listed on the label.5 So it is important to use a therapeutic, veterinary-distributed hypoallergenic diet in treating or testing for food allergy. It appears that with therapeutic hypoallergenic diets, the ingredients are more or less guaranteed to be what the label states.

Secondary factors

Because of the defective skin barrier present in atopy, which doesn't allow the normal bacterial flora (or yeast) to be kept in check, it is important to address the secondary bacterial or yeast component in atopic patients. Using antibiotics, antiyeast medications or antibacterial-antiyeast shampoos can help alleviate clinical signs. Miconazole formerly considered in yeast-fungal infections has now been found to have antibacterial properties.6

Contact time with shampoos should be a good 10 to 15 minutes. Most antibacterial-antifungal shampoos do not lather well, so owners do not feel they're effective. Tell owners not to keep using more product to generate a lather; it will never happen. And be sure to ask the owner about the patient's response to shampoos since not every dog with yeast responds to antiyeast shampoos, and some may actually be irritating. We don't want to make the dog worse with bathing.

I usually start with a hypoallergenic shampoo just as a cleansing shampoo and have clients spot-test the more medicated shampoos to be sure no adverse reactions occur. Stripping shampoos such as those that are tar-based are rarely needed in atopic patients.

If systemic antibiotics are used, be sure to treat long enough and without corticosteroids if possible. Sometimes even a tiny dose of systemic corticosteroid will compromise the full potential of the antibiotic. Topical corticosteroids are favored over systemic corticosteroids. Low-potency topical corticosteroids are preferred over long-acting sprays, which most owners tend to overuse. Oral antifungals such as ketoconazole or fluconazole can help control the secondary yeast overgrowth and can usually be reduced to two times a week as a maintenance.

Immunotherapy pointers

If you are using immunotherapy, either injectable or sublingual, remember that flare-ups are not unusual. Owners must be made aware of this as they often have high expectations that the immunotherapy will take care of everything.

Sublingual immunotherapy for atopic dogs has recently become available. It has a similar success rate to injectable immunotherapy (60 percent to 75 percent) and offers advantages in that it is available as oral drops, can be effective in three to six months, does not need refrigeration, and anaphylaxis is not commonly seen (it is reported in 1 percent or fewer of injectable immunotherapy patients).7

My clinic has been using sublingual immunotherapy in patients for more than a year with good results. But as with any type of immunotherapy, nothing is "cookie cutter." Individual patients will vary with their response, ranging from the initial vial being too strong (causing more pruritus) to some patients being maintained on the lower-strength vials and not having to proceed according to schedule.

Just keep in mind that once immunotherapy is dispensed, individual monitoring is essential, and the owner should be checking in routinely or notifying you of any increase in pruritus or flare-up of otitis or bacterial pyoderma. Clients often mention to me that immunotherapy solutions are dispensed to them without any follow-up or reactions to watch for. Even though instructions are available with the immunotherapy, it is essential for you or a member of your staff to sit down and go over instructions—what to watch for and how often or when to contact your office.

Conclusion

Allergy problems are never easy, and in most cases they are there for the long term. Establishing a safe, long-term method of treating these atopic patients is essential in order to provide them with a good quality of life. As mentioned above, topicals such as shampoos and ceramide replacers, diet changes and good communication are small ways of enhancing a pet's response to a long-term therapy.

Minimizing corticosteroid use is important, but when a flare-up occurs, corticosteroids are needed for the short term to get the pet back on track. But be "steroid-stingy"; once you dispense corticosteroids, instruct the owner on the short length of time they are to be used and dispense only small amounts. Many clients see the patient doing well on corticosteroids and continue to use the medication long term, which brings about other problems that didn't exist in the first place.

There is no one magic potion for allergy but instead a combination of medications that is unique for each patient. It's just achieving that right combination that's the trick!

Dr. Alice Jeromin is a pharmacist and veterinary dermatologist in private practice in Cleveland, Ohio. She is a graduate of The Ohio State University College of Veterinary Medicine.

References

1. Marsella R, Sousa CA, Gonzales AJ, et al. Current understanding of the pathophysiologic mechanisms of canine atopic dermatitis. J Am Vet Med Assoc 2012;241(2):194-207.

2. Cork MJ, Danby SG, Vasilopoulos Y, et al. Epidermal barrier dysfunction in atopic dermatitis. J Invest Dermatol 2009;129(8):1892-1908.

3. Piekutowska A, Pin D, Reme CA, et al. Effects of a topically applied preparation of epiderma lipids on the stratum corneum barrier of atopic dogs. J Comp Pathol 2008;138(4):197-203.

4. Glos K, Linek M, Loewenstein C, et al. The efficacy of commercially available veterinary diets recommended for dogs with atopic dermatitis. Vet Dermatol 2007;19(5):280-287.

5. Raditic DM, Remillard RL, Tater KC. ELISA testing for common food antigens in four dry dog foods used in dietary elimination trials. J Anim Physiol Anim Nutr 2011;95(1):90-97.

6. Weese JS, Walker M, Lowe T. In vitro miconazole susceptibility of methicillin-resistant Staphylococcus pseudintermedius and Staphylococcus aureus. Vet Dermatol 2012;23(5):400-e74.

7. DeBoer DJ. Sublingual immunotherapy for atopic dermatitis. Clinician's Brief June 2013.