© 2023 MJH Life Sciences™ and dvm360 | Veterinary News, Veterinarian Insights, Medicine, Pet Care. All rights reserved.
Therapies to get patients through a tough allergy season
This allergy season in the Midwest appears to be one of the worst in memory.
This allergy season in the Midwest appears to be one of the worst in memory.
Patients that usually begin symptoms in April or May had already started them in March. A possible explanation might be that, because the Midwest had an extremely mild winter, some patients never had the winter break from allergic problems.
Atopy in a 5-month-old Irish Wolfhound. The perception is that onset is occurring at an earlier age.
This article offers some ideas that might help your patients this year. Some are reminders; others may be new, and some are a combination of the two.
Bathing and topicals
If nothing else, frequent bathing mechanically removes pollen from the coat and skin. In human allergy there is evidence to show that percutaneous absorption of pollen occurs to get the allergic reaction started; therefore bathing may be even more important for allergic dogs and cats.
Because pets tend to absorb more substances through hairless parts of the body (i.e., footpads, groin, medial pinnae and perineum), it is a good idea to rinse those areas more often during pollen season. Rinsing – not soaking – is important because soaking causes maceration of the skin; substances are more readily absorbed through waterlogged skin.
Bathing reduces the number of skin bacteria, already higher in allergic dogs and in warm weather. Also, it reduces secondary seborrhea and odor. A general cleansing shampoo is helpful; so are oatmeal-based shampoos or those containing pramoxine.
Antibacterial bathing with benzyl peroxide or chlorhexidine, for pets with bacterial pyoderma, along with allergy or miconazole/chlorhexidine shampoos for patients with secondary yeast dermatitis, can help with pruritus.
Topicals containing low-dose steroids are helpful. Use them once or twice daily to skin folds such as the axillae, groin or ventral neck fold where so many atopics tend to flare.
The topical Resicort can be diluted 4 capfuls/1 C water and used as a spray daily or as an after-shampoo, leave-on rinse. I favor less-potent topical steroids such as Resicort because owners tend to overdo topicals and may overuse more potent triamcinolone-containing products. If these products are dispensed, do so with explicit instructions.
Leave-on antipruritic, non-steroid rinses (such as relief cream rinse) can be helpful. Oil-based products should be avoided because yeast favor oil for growth. For focal areas of pyoderma, mupirocin 2% ointment can be used twice daily.
Because the skin of allergic dogs (and humans) tends to attract bacteria more than nonallergenic dogs, antibiotics are essential in treating the pyoderma that most often accompanies allergy.
Bacterial pyoderma by itself can be pruritic in some patients. It is always a good idea to treat with antibiotics alone or in combination with antihistamines, avoiding steroids. Even a small dose of steroid combined with antibiotics may immunosuppress the patient enough that the pyo derma will not resolve. Be sure to treat the pyoderma until it is totally resolved, then add an additional week.
Note the chronic skin changes in an atopic dog from constant foot licking. (Top); Yeast dermatitis can present in the muzzle folds of an atopic dog. (Center); An acral lick granuloma on the foreleg of an allergic Poodle. (Below)
If you find that the antibiotic helps with the pruritus yet the patient flares without it, consider pulse-dosing the antibiotic (i.e., one week on/one week off).
Recall also that antibiotics such as penicillin, ampicillin and tetracycline have little activity against Staph intermedius. As mentioned previously, bathing with antibacterial shampoos not only can be preventive but, along with the appropriate antibiotics, can bring about a more rapid reso lution of the pyoderma.
With deep pyoderma that accompanies allergy, be sure to check skin scrapings so you don't miss demodex mites. Demodex mites can occur secondary to allergy and particularly in those patients kept on steroids for their allergy. Steroids are contraindicated in patients with demodicosis.
Since atopics not only have bacteria as an accompanying factor in allergy, yeast in some patients can be equally common. Since most atopics have ear involvement and lick their feet — two places where yeast is most-often found — it is important to check ear smears and nailbed/skin smears, especially of folded areas (axillae, groin, chin folds, nailbeds).
In some atopics, treating the accompanying yeast gives the pet a good deal of relief. Breeds that tend to have yeast as a primary factor or a complicating factor of atopy include Cocker Spaniels, Shih Tzus, Lhasa Apsos, Golden Retrievers, Labrador Retrievers, Basset Hounds, Beagles and Poodles.
In patients with facial pruritus, especially periocular lesions, be sure to check ear smears. When treating the yeast otitis with topical miconazole or clotrimazole, sometimes including a topical steroid for the localized yeast hypersensitivity that can occur, as well as antiyeast bathing in chlorhexidine, miconazole or benzyl peroxide can reduce pruritus.
Often, however, a systemic antiyeast medication such as ketoconazole 2.5-5mg/kg bid is helpful. A small percentage of humans taking ketoconazole develop elevated liver enzymes, but this occurs less frequently in dogs. Still, it is a good idea to monitor liver enzymes, particularly in patients on long-term maintenance doses (i.e., MWF or twice a week).
Many patients can be maintained even below published doses. The fact that the main adverse effect of ketoconazole in dogs is vomiting and diarrhea is good reason to start at a low dose and increase later if necessary.
Within the context of this article, immunotherapy refers to desensitization, hypo sensitization and allergy injections.
If you have a patient who is maintained on immunotherapy but flares during warm weather, schedule a recheck to rule out ecto parasites, bacterial infection and yeast infection.
Perhaps no lesions or ectoparasites are found, yet a once well-controlled dog has become pruritic. He/she may be getting too much antigen during the affected season. I often have the owner skip a dose of allergy injection and call me with the response. If the patient was less itchy without the injection, then I reduce the amount of the injection by 50 percent.
Conversely, if, when beginning injections, the patient is more pruritic after the injection, we will also skip a week and proceed at 50 percent of the dose the following week.
What we like to hear is that, after the injection, the patient is less itchy, then starts with pruritus as the next injection is due. In some patients where the injection seems to hold them for a few days, we will administer the injection twice during the injection period until we can get them stable.
In patients that are only outdoor-pollen allergic, I prefer to start immunotherapy in the late fall after the majority of their allergy season is over. It is too difficult to try and monitor their responses to the injections if you are administering what they are allergic to during their affected season.
In some atopic patients, recurrent bacterial pyoderma is a symptom of underlying atopy but that can be true of hypothyroid patients too. I have had patients who responded well to immunotherapy, then became non-responsive once they became hypothyroid.
In middle-aged and older dogs that we are working up for atopy, checking for hypothyroidism is part of the workup. We check a T4 and if borderline, a FT4 TSH (15 percent to 30 percent of hypo thyroid patients can have a normal TSH). T4 values can be artificially reduced if the patient is receiving sulfas, NSAIDs, steroids or anticonvulsants, so be sure to take that into consideration. Some dermatologists believe patients with acral lick granulomas (also seen with atopy) can be hypo thyroid.
Much has been written on the potential benefits of fish-oil (omega 3, 6) supplementation. Omega 3 supplements have been shown to help with pruritus, and omega 6 supplements can help with skin and coat quality.
In atopy, because pruritus and changes in skin and coat quality (i.e., lipid changes in the epithelium) occur, I prefer to use a product with a mixture of both omega 3 and 6 fatty acids. I find that these supplements can take several months to become effective, so it might be a good idea to start the atopic patient off on these immediately.
One mistake that clients make is discontinuing the product after the usual 60-day supply is completed, either because the dog is doing well or because they feel the product is not working. In either case, it needs to be explained that these supplements may be more preventive than thera peutic, at least initially when building up to an effective level.
Some evidence shows that combining fatty acids with an antihistamine may in fact increase the rate of reducing pruritus. These supplements can be helpful particularly in clients that want to employ "natural" and/or non-drug means to treat their pets.
Many owners administer antihistamines without first consulting veterinarians, thereby giving too low a dose. Or they may use one of the newer antihistamines that do not yet have recommended doses.
Antihistamines in the atopic dog reportedly are successful about 10 percent to 30 percent of the time, although I have not seen that high a success rate in my practice. However, because antihistamines are a better choice than steroids, veterinarians continue to dispense them with the hope that they will be effective.
Some of the newer antihistamines and their doses for dogs include: Claritin 10mg tablets (loratidine) — 0.5mg/kg sid; Clemastine 1.34mg. tablets – 0.05mg/kg bid; Allegra 10mg if <10kg, 20mg if 10-14kg, 60mg if >25kg body wt. sid.
Old standbys include: hydroxyzine 1mg/lb body wt b-tid; diphenhydramine 1mg/lb body wt b-tid; chlorpheniramine 2-12mg b-tid; amitriptyline 1-2mg/kg s-bid; doxepin 1-2mg/kg sid.
Most dermatologists believe an adequate trial is 14 days, then if not effective change to another antihistamine of a different chemical class.
Antihistamines are not without side effects, and they should be used with caution in breeding dogs and those with seizures, glaucoma and cardiac problems. Antihistamines can be helpful when used with a combination of therapy for atopy such as immunotherapy, fatty acids and bathing.
Nothing has revolutionized therapy for atopic dogs recently more than cyclosporine. Whereas some patients that were nonresponsive to immunotherapy or relied on steroids to maintain their condition, cyclo sporine appears to be an important alternative.
Perhaps the most important qualification for using cyclosporine is the determination that the patient is, in fact, atopic. It sounds elementary but as always with the diagnosis of atopy, a good dermatological history is important, including age of onset, seasonality vs. non-seasonality, breed of dog, areas of the body affected and, in some patients, response to steroids.
A diagnosis of atopy is confirmed by a good history and ruling out the other differentials of atopy, including ectoparasites, food allergy, bacterial pyoderma, yeast dermatitis and hypothyroidism. Atopy is not confirmed by a positive serum test or by a positive skin test because some non-atopics will test positive for allergy and 5 percent of atopics will have negative skin and blood tests.
The main side effects we have seen with cyclosporine at 5mg/kg/day is vomiting and diarrhea, so I will start some patients at a lower dose, particularly those with a sensitive GI tract.
In some patients that still experience vomiting on a low dose of the cyclosporine capsule, changing to cyclosporine oral liquid (100 mg/ml) or adding Pepcid AC to the regimen may be advised. Most patients will respond in 30 to 60 days, and some patients are able to go on an every-other-day regimen or less. Long-term effects of cyclosporine include gingival hyperplasia (usually reversible upon discontinuation of the drug), papillomas, neutropenia and hypoalbuminemia.
When yeast accompanies atopy, lower doses of cyclosporine may be possible if ketoconazole is added to the regimen. There is no set dose of ketoconazole that will prolong cyclosporine in each patient; it appears to be individual.
Cyclosporine for atopy appears to be a work in progress, and we still are adding to the list of side effects seen with long-term use. Some owners will start using cyclo sporine for the more rapid relief of allergy symptoms, then elect to start immunotherapy injections because of the expense.
While steroids can give immediate relief to atopic patients, the key is to use them infrequently, at low doses (preferably short-acting and every other day) and monitor their use.
Because they do tend to work well, owners get in a habit of administering them as a daily routine without regard to whether the pet actually needs the drug.
Soon you have an iatrogenic Cushingoid dog that you as the veterinarian see, but the owner has no idea what they've created. So be stingy in dispensing steroids and maintain close communication with the owner, so that the dog is not on prolonged steroid use.
One way to use less steroid is to change to Temaril P, which is a combination of anti histamine (not to be used in seizure patients) and steroid. It can be a good first attempt of getting a patient from using prednisone 20mg daily to one or two tablets of Temaril P daily, which would total 2 mg to 4 mg prednisolone daily — quite a reduction.
Short-term use of low-dose, alternate-day, short-acting steroids such as prednisone may be acceptable in getting the atopic patient through a tough few weeks of their season, but now that cyclosporine is available as an alternative, or even topicals such as Resicort may suffice, try those first instead.
Alice Jeromin DVM, Dipl. ACVD
Dr. Jeromin is a pharmacist and veterinary dermatologist in private practice in Cleveland, Ohio. She is a 1989 graduate of The Ohio State University College of Veterinary Medicine and an adjunct professor at Case Western Reserve University's College of Medicine in Cleveland.