ALLERGIC DERMATITIS AND OTITIS (ALLERGIES)

Overview:

1. Consider not breeding allergic pets.
2. Start treatment early for a better response.
3. All secondary infections must be treated!
4. Avoid common allergens.
5. Rinse off pollens, bacteria, yeast, and dander with baths every 3-7 days.
6. Limit the flea allergen burden by the use of flea control monthly year-round.
7. Reduce food allergen burden by performing an exclusive food trial.
8. Use symptomatic therapy (oral and topical) to help reduce signs of itch (eg, fatty acids, antihistamines, moisturizers).
9. "Allergy" testing with allergen-specific immunotherapy is the safest long-term treatment.
10. Cyclosporine therapy is highly effective and can be used alone or combined with other therapies.

Above information provided by Hnilica, KA.

As allergic skin and/or ears become inflamed (dermatitis and otitis, respectively), secondary infections (bacteria and yeast) take residence on the surface. Infection may cause worsening of itch, hair loss, scaling, pimples, discharge, scabs, discoloration, elephant-like skin, greasiness, and/or a bad odor. These signs may resolve with antibiotics and antifungals, but recur in weeks to months after discontinuing therapy. Controlling for these infections is only the tip of the iceberg when managing allergies. Unless the underlying allergic reason(s) for the infections is identified and managed, infections will continue to recur. Additionally, other underlying conditions (eg, endocrine and scaling disorders) can cause relapsing and remitting infections. Therefore, a thorough dermatologic history, examination, and diagnostic/therapeutic trial(s) (eg, antimicrobials, flea control, mite trial, novel protein diet trial, skin testing, allergen-specific injections) are required to get to the root cause of a patient's signs. Unfortunately, this systematic approach may take weeks to months before a diagnosis is made or improvement is seen.

It is important to remember that allergies can be managed, but not necessarily cured. Consequently, several therapies (oral and topical) may be prescribed for a patient as there is not a single wonder drug for allergies. A comprehensive therapeutic plan attempts to get as many benefits from a selection of drugs while decreasing the risk of their side effects when prescribed alone at higher dosages. This is true for people with allergies as well. A goal we strive for is to reduce itch by 80-90%, about 80-90% of the time. As the allergic signs are controlled, the frequency of secondary infections is improved. It will require the combined efforts of the patient, client and veterinarian(s) to reach this goal. Since there is a genetic component involved in the development of allergies, it is generally recommended that affected pets are not bred.

Two important concepts to understand when managing allergic dermatitis and/or otitis are:
Pruritus (itch) is additive. Every individual has a different pruritic threshold. Simply put FLEAS+DRY SKIN+INFECTION+MITES+FOOD ALLERGIES+ENVIRONMENTAL ALLERGIES+CONTACT ALLERGIES=COMBINED WORSENED STATE OF ITCH COMPARED TO EACH CAUSE ALONE. In order to provide relief to your pet, we need to control as many causes of pruritus as possible to get your pet below his/her itch threshold.
This means we do not have to identify and control everything an individual is allergic to, just enough to get below the pruritic threshold (subclinical). Four of the most common underlying causes of pruritus are allergies to fleas, Sarcoptes mites, food, and the environment. Allergic contact reactions are rare in veterinary patients as their coat provides a barrier to many contactants.

FLEA ALLERGIC DERMATITIS (FAD)

Fleas are the number one cause of pruritus in dogs and cats; however most owners are initially in fleanial. Animals allergic to fleas need not be infested with fleas, only exposed to a few flea bites. Exposure may occur in the indoor (eg, carpets, bedding, other animals) or outdoor (eg, grass, underbrush, other animals) environment. FAD often manifests as itchy skin along the tail base, rump, and groin in any aged pet. Animals may also have recurring "hot spots". Typically, FAD is worse during the more warm and humid times of the year. However, it can be a year-round problem especially during mild winters. Even if an animal is not truly "allergic" to fleas, fleas can perpetuate other allergies. Therefore, most all pruritic animals will need a topical flea preventative to reduce the number of flea bites. For those animals with only FAD, topical flea preventative may be curative. In-contact pets should be treated as well since they may be the source of fleas.

SARCOPTIC MANGE (SCABIES)
Hypersensitivity to this mite (burrowing microscopic tick-like organism) is often overlooked as a reason for pruritus. This is not surprising as the mite is extremely hard to find with skin scrapings. Pets get this mite from other infected animals (dogs, fox, etc.) that may be subclinical for the condition. Hypersensitive pets usually are severely pruritic along their ear margins, armpits, groin, and extremities. Excluding this mite as a cause of itch is made by response to anti-mite therapy (up to 8 wks). Ideally, all in-contact pets should be treated as this mite can jump to other untreated animals
possibly propagating the condition. If the other pets are not treated then they should at least be separated form the one being treated. Since the mite cannot survive for long periods off of a host, environmental control measures are usually not required. Insecticide sprays can be used when needed to treat the environment, but please contact CVDA or your veterinarian before using a product as some can be toxic to animals. This mite can infest the skin of humans. Lesions on people usually present as itchy red bumps (papules) on the forearms and trunk. If you think you have these lesions, contact your physician. The feline sarcoptic mite is called Notoedres.

CUTANEOUS ADVERSE FOOD REACTIONS (FOOD ALLERGIES)

Animals allergic to food, usually protein (eg, beef, dairy, lamb, chicken, etc.), can develop signs of itch at any age. Usually their itch is year-round as they are constantly exposed to food allergens. Some animals may respond to steroids, but this response is highly variable. Food allergic animals present with pruritus affecting the face, ears, paws, armpits, groin, and/or rump. Some animals have only skin disease while others have only ear disease. Additionally, they tend to develop chronic and recurrent infections on their skin and/or in their ears which need to be controlled. A few animals might experience episodes of vomiting, diarrhea, or increased frequency of defecation as well. Blood and skin tests to foods have failed to identify this population of allergic animals. Consequently, the only way to diagnose food allergies is by feeding the pet a novel diet for up to 12 weeks with subsequent "old" diet challenge. During a diet trial the pet will not be allowed to eat milk bones, rawhides, table scraps/people food, other pet food, or flavored medication. If the pet improves while on the diet trial (remember infection needs to be controlled too), but relapses upon diet challenge then food allergies is likely contributing to the pet's pruritus. If this is the case, the novel diet will need to be fed long term or another diet to which the animal is not allergic to should be fed as determined by an individual ingredient challenge.

ENVIRONMENTAL ALLERGIES (ATOPY, ATOPIC DERMATITIS)

Pets may be allergic to pollens (eg, trees, grasses, weeds), dander, molds, insects, and housedust mites. Atopic animals usually develop signs of pruritus and recurring skin and/or ear infections between 0.5-3 years of age. Many times their signs are initially seasonal but progress with each season to become year-round (nonseasonal). Typically these animals are very steroid-responsive. Clinically, these pets look like ones with food allergies meaning the same body areas are affected. This disease is diagnosed by the exclusion of other causes of pruritus. Once diagnosed, skin and/or blood allergy tests can aid in the identification and selection of allergens to "desensitize" your pet. Desensitization (immunotherapy) is accomplished by injecting the specific allergens to which the animal is allergic to in hopes of dampening the immune response to harmless allergens. About 60-80% of animals respond to immunotherapy (best long term solution), but it may take up to 1 year to see improvement. Regardless of the response, many of these pets may still require the benefits of other therapies (oral and topical), including flea preventative, antihistamines, fatty acids, steroids, and/or other immune-modifiers (eg cyclosporine) albeit at lower doses and frequencies. NOTE: Steroids are the most commonly used and abused drugs. However, when used appropriately for pruritus (eg, low dose every 2-4 days for proper duration) their benefits can outweigh their risks.

Allergen avoidance and control measures can also be helpful for the pet allergic to house dust, house dust mite (HDM), molds, feathers, and pollens. HDM are microscopic tick-like organisms that live in pillows, mattresses, pet beds, fabric upholstered furniture, stuffed animals, carpets, and rugs. These mites, a common cause of both animal and human allergies, feed on dust dander. Covering bedding material in impermeable covers, not allowing the pet into areas where dust accumulates, frequent vacuuming/dusting (while pet is outside), frequent linen washing (hot water), and removal of carpets/rugs/pet bedding can help reduce the numbers of HDM and dust load. Keeping the pet away from basements, closets, laundry rooms, bathrooms, crawl spaces under the house, house plants, freshly mowed grass, hay, leaf piles, barns, and pet food bags will help reduce exposure to molds. Removal of feathers (eg, pillows, comforters) and birds help those allergic to feathers. Confining the pet indoors at dusk and dawn during heavy pollen seasons, keeping the grass cut short, mowing while the pet is indoors, and rinsing the pet off after periods in fields and grass can help reduce the pollen burden your pet faces. While most of these strategies are not completely effective at reducing allergic signs, they do improve the response of your pet to other therapies employed.

Highlights:

1. Most types of allergies can be managed, but not necessarily cured.
2. More than 1 type of allergy can exist in a given patient.
3. Diagnosis is made by history, clinical findings, and exclusion of all causes of pruritus.
4. A definitive diagnosis may take weeks to months to make.
5. Reaching a definitive diagnosis and selecting specific treatments will be more successful in the long-term, and often less expensive.
6. Diagnostic tests may include cytology, skin scrapings, response to topical flea preventative, response to anti-mite therapy, response to antibiotherapy, skin/ear culture, elimination diet trial, skin testing, blood allergy testing, and skin biopsy.
7. There is no wonder drug for allergic dermatitis. Therapy is tailored to each individual.
8. All infections must be controlled!
9. Periodic flare-ups will occur.
10. A goal is to reduce pruritus by 80-90%, roughly 80-90% of the time.