Allergy – a hypersensitive state acquired through exposure to a particular allergen

- an over response of the immune system to the presence of an otherwise harmless substance (allergen)

- in pet animals this response commonly causes skin symptoms (itching, redness, swelling, thickening, etc). Only occasionally do allergies in pets cause respiratory symptoms, more commonly in cats.

- allergies are considered an inherited tendency and therefore we recommend spay/neuter of confirmed allergic animals


TYPES OF ALLERGIES - 4 Categories:

1) Flea bite allergic dermatitis – Most common, often seasonal, fleas not always present, often “punctate” pattern of red, centrally crusted skin lesions often around the rump, tail head, back of the thighs, bottom of the abdomen.

2) Atopic Allergic Dermatitis (Inhalant) – 2^nd most common, usually seasonal, hair loss and itching around eyes and face sometimes, paws/digits involved, onset usually < 3 yrs

3) Food Allergy Dermatitis – non-seasonal, unrelenting, often chronic ear infections associated, very generalized pattern, often secondary bacterial or fungal infections.

4) Contact allergic Dermatitis – rare, usually affects sparsely haired common contact skin surfaces

Animals subject to allergies usually have multiple antigens they are sensitive to, often from multiple categories, i.e. they can be      allergic to fleas, airborne allergens and certain foods at the same time. The specific antigens they are sensitive to may increase or decrease (rare) over time. Allergic symptoms are the additive effects of all the antigens an allergic animal is exposed to at any    given time.    


SECONDARY SKIN PROBLEMS: May be diagnosed initially as the primary problem until the root cause is recognized and may include: bacterial and/or fungal skin infections, ear infections, hair loss (alopecia), skin darkening (hyperpigmentation), skin thickening (hyperkeratosis), seborrhea (oily skin), mange, pododermatitis (infections of the skin of the paws), lick granulomas, “hot spots”, etc.


DIAGNOSIS OF ALLERGIES – Allergies are often initially a presumptive diagnosis made with symptoms and the rule out of other diseases. Rule outs may include mange, bacterial or fungal infection, hormonal disease such as thyroid problems or Cushings Disease (hyperadrenocorticism), and autoimmune disease such as pemphigus or lupus. A typical work up for allergies could include skin scrapings, bacterial and/or fungal cultures, blood testing, and skin biopsies. Ultimately, specific allergy testing, as discussed below, is the definitive diagnostic test.

ALLERGY TESTING (2 types)

1) Interdermal Testing – gold standard, usually performed by dermatologists, antigens are injected into the skin of the test subject and observed for reaction.

2) Pet ELISA testing – blood test, reasonably accurate, local laboratory, can  include inhalant allergens, both indoor and outdoor, food allergens, insect     allergens, molds, dust mites, etc. Accurate identification of the allergens involved in the allergy is critically important. Testing often leads to hyposensitisation therapy (see below).


THERAPY

Goal of Therapy: The goal of therapy in veterinary medicine in practical application is to do everything possible to reduce the long term use of systemic steroids (injections or pills) so as to minimize side effects. Using steroids for short term “flare ups” is, in this practice, acceptable. We refuse to repeatedly give long acting steroid injections.

Most treatments involve a combination of methods to reduce itching especially in the early course of the allergy. When allergies become severe, hyposensitization or the use of cyclosporine should be strongly considered.

Treat Secondary skin disease aggressively!

Antimicrobials – Antibiotics vs antifungal vs both

Underlying Metabolic Disease – Hypothyroidism, Hyperadrenocorticism, Diabetes, Autoimmune (pemphigus, lupus), Neoplastic (skin cancer)

Mange Treatment, etc.

1) Avoidance: Remove offending allergens from the pet’s environment. Applicable with flea, food and contact allergies. With inhalant allergies is almost impossible.

Food trials:  a minimum of 8 weeks duration, must be extremely strict, consider cat food, other dog’s food, feces consumption?, neighbors, treats of all kinds, heartworm preventative, infants or young children dropping food or giving treats, ……difficult to be conclusively negative.

Flea Treatment – Critical!
We must treat all other possible hosts such as other dogs and cats in the household. Our treatment must be effective and safe. Over bathing will often make skin itch more due to the removal of natural skin oils.

Indoor vs Outdoor, bedding choice, Air treatments  

2) Topical Treatments

Shampoos: Can be helpful as long as not overused.

Relief Shampoo^®: Contains a topical anesthetic, pramoxine that simply deadens the skin to temporarily relieve itching.

Colloidal oatmeal shampoos: removes the offending antigens from the skin.          

Ointments/Sprays/Powder: Topical steroid preparations like Cortaid^® or Hydrocort 10^® can be very useful parts of a program of treatment to reduce symptoms but must be applied 3 – 4 times daily. Topical antihistamine ointment like Benadryl^® ointment can also be useful. We will often dispense a prescription ointment that has both antibiotics and steroids. The topical use of steroids avoids the side effects commonlyassociated with long term systemic steroid use.

3) Systemic Anti- itch medications – Antihistamines, Anxiety medications, Pentoxifylline (expensive),  Melatonin +/- (hair issues), Acupuncture?

We recommend the aggressive use of antihistamines with almost all inhalant allergies as there are few side effects, they are inexpensive and at worst will   reduce the amount of steroids that are needed to control symptoms.

Dose: Diphenhydramine (Benadryl^®) for Dogs: 1 - 2 mg/lb up to 3 times daily. Dosages of other antihistamines are available.

4) Supplements - EPA/DHA (fish oils) – These fatty acids have been shown to have a wide variety of health benefits which include anti-inflammatory effects, as in allergies and arthritis. These supplements are available both for humans and pet species in the form of capsules, chews, or liquid or can be an ingredient in certain diets.

5) Immunomodulating Drugs

Steroids (glucocorticoids) – Lots of side effects, especially with long term use including opportunistic infections (skin, urinary, respiratory, GI), muscle wasting, PU/PD, hyperpigmentation, cartilage degradation, liver damage (“hydropic degeneration”) and more. Steroids are “The Hormone of Stress”.  Their long term use hormonally simulates the effects of stress on the body.

“Atopica^®” = Cyclosporine – Approved for use in dogs for allergic symptoms. Can be used alone or in combination with steroids – expensive but very effective and has been a life saver for many patients.

6) Hyposensitisation – Controlled exposure of immune system to reactive antigens in increasing dosages to affect a more appropriate immune response to their presence. It is most effective with inhalant antigens. Approximately 60 – 70% effective. Advantage: Treats the true cause of the problem instead of simply treating the symptoms.

After accurate identification of the offending antigens, solutions of those purified antigens are made up and given as injections in ever increasing amounts. These injections can be given at home (after training on how to administer them) and follow a very specific schedule. The attempt is to “desensitize” the immune system. This can be very effective but because of the amount of commitment it requires, both financial and time, is usually reserved for moderate to severe allergies.