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Dermatology - Atopy & Food Allergy

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sihirlifil's version from 2017-08-27 21:26

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Question Answer
Etiology of atopyDogs are predisposed to making IgE, causing allergies to environmental contaminants via inhalation, percutaneous absortption
How is a dog sensitized to (& elicit) allergens?(Usually seasonal) Exposed during the first year, then show CS when challeneged again second year
Atopy: onset?Over 1 year old Need to be sensitized first
Atopy: breed dispositionsTerrier, labrador retriever, maltese, mutt
Atopy: distribution patternFace (muzzle, periorbital), feet, ears, axillae, forelegs
How is a dx of atopy made?Based on HISTORY & CS e.g. distribution & seasonality (no skin test!!)
Signs of pruritis?Licking, chewing, rubbing, biting, scratching, head shaking, plucking hairs
Brown staining = Salivary porphyrins (sign of pruritis)
Secondary complications of atopy:Pyoderma, otitis, seborrhea, Malassezia, conjunctivitis
Most common cause of recurrent pyoderma:2ry to Atopy
What does lichinification indicate?Chronicity (**cytology**)
Feline atopy: onset?1-3 years but can develop when older
Feline atopy: distributionHead, neck, pre-aural
Feline atopy: CSINTENSE prurities --> excoriations, excessive grooming
T/F you should not do allergy testing if you suspect atopyT. No allergy testing unless you plan on putting patient on allergy shots. Allergy test does not confirm dx of atopy
Consider allergy shots whenPatient needs to be on steroids / meds just to have good quality of life (e.g. behavior change from itching all the time)
Really bad 3/4 of the year
Recurrent pyodermas & always pruritic even when not infected
Owner is willing to give injection / sublingual daily
Gold standard allergy testIntradermal skin test
How is in intradermal skin test done?Inject allergen into skin, mast cells will degranulate if IgE specific for an Ag is present --> wheals (type I hypersensitivity). Compare to positive control (histamine) & negative control (saline). Check for correlation with seasonal allergens
What do you need to do before allergy testing?Drug withdrawal. 30 days for steroids (they stabilize mast cells), antihistimines, fatty acids; 90 days if injection
Advantages of serum testingNo need for sedation, clipping, or withdraw drugs; cheaper
Disadvantages of serum testingBlindly trusting company, still have to make sure results fit the hx (yak...? Lol), takes a long time, can't use for food allergies
Mild therapies for pruritis:Antihistamines - diphenhydramine, hydroxyzine (sedating properties helpful)
Low dose TCA (amitriptyline, doxipen)
Fatty acids ((mostly anti-inflammatory, drives anti-PG)
Tx for 8-9-10/10 pruritis? How much do we want to give?Prednisone
Lowest possible dose every other day
Nice thing about Prednisone?WILL WORK for atopy as well as possibly food, mite, etc! Very steroid-responsive. If dog doesnt respond to pred, it isn't atopy (2ry bact infxn, flea allergy type 4 hs rxn, scabies, food allergy...)
What is Temaril-P? Drawback?Combo of Pred & antihistamine. Good for atopics that flare only a few months out of the year (low dose, short term)
Only really works well for atopy
Long-term therapy: cyclosporine. Considerations? how long to effx?Immunosuppressive (not so good long-term, but fewer SEffx than pred)
Takes weeks to effect, should use additional anti-itch drugs until then. Only works on atopy
Long-term therapy: cyclosporine. How do you give it?1 a day until effect, then drop to every other / every 3rd day
Don't cut dose! (Tx failure)
T/F a patient on cyclosporine should also be allergy testedT
Ideal cost-wise if owner compliance
Oclacitinib: Who can get it? how is it given?>1 year!
Give BID x 14, then once a day for maintenance. Good for short-term
Oclacitinib: What do you have to make sure you do with a patient on this drug?Monitor! CBC (BM suppression --> anemia) (Affects JAN-K signaling pathway)
Oclacitinib: Advantages?Doesn't interfere with allergy testing (don't need withdrawal period)
Not a steroid, so no PU/PD, muscle wasting...
Oclacitinib: Contraindications?Hx of cancer or demodex! ALSO not approved for cat! dont do it
Canine Atopic Dermatitis Immunotherapy:Cytopoint
Cytopoint: what is it? what does it do?Canine IgG monoclonal Ab
Binds to IL-31 (cytokine that causes pruritis) and blocks binding (Apoquel is similar; allows binding butblocks msg to nucleus)
Cytopoint: how is it given?SubQ injection q21-30 days
Good for short-term, esp. in combo with cyclosporine (give 1 injection when starting cyclosporine, so it can work while cyclo kicks in)
Cytopoint: downsides?$$$ 1 injection = $70
Hyposensitization: need? advantages?Good owner compliance! Cheap, very safe, works well, helps reduce incidence of recurrent infection
Hyposensitization: downsides?Takes 4-6 months to work. Need to commit to 1 year before giving up (owner compliance)
Topical therapy: types?Oatmeal based
Anesthetics
Corticosteroids
Cool water (help remove allergens, reduce inflammation)
Food allergy: Type of hypersensitivity?Can be I, III, or IV
Age onset of food allergy:Any! Sometimes very young, e.g. terrier, spaniel, shar-pei (Atopy = 1-3 years)
T/F Food allergies are seasonalF. No waxing/waning (always eating same food)
If a patient responds poorly to Pred, top differential = Food allergy (less common than atopy though)
Food allergy: distributionSAME AS ATOPY!
Food allergy: CSUrticaria, GI symptoms (can have only derm, only GI, or both), seizures (idiopathic epilepsy), infections; recurrent ear infxn on 1 side (weird)
Test for food allergy:Food trial = gold standard
Diagnosis of food allergy based on:Non-seasonal pruritis, CS, dietary Hx, (lack of) response to steroids
Unique behavioral thing about atopy?Will stop itching if owner asks. With food allergy, scabies, fleas etc, don't stop itching
What is in an elimination test diet? How is it done?Novel protein & carbohydrate (never seen Ag before). Feed for 8 weeks (takes that long to 'flush old food out of system'), and NOTHING ELSE PER OS! (owner compliance issue). Then re-challenge with the old food
What is hydrolyzed protein?Part of elimination diet. Broken down protein, too small to be antigenic (but can still be haptens if they bind to protein!)
Only way to definitively dx food allergy:Elimination test diet (novel protein, carb)
On an elimination diet: DO NOT GIVEFlavored heartworm medications, rawhides, pigs ears, milk bones, treats, ANYTHING!
Examples of food trial foodsPurina HA (he eats it in front of clients, it has no taste), Hills ZD (hydrolyzed chicken so not great), Royal Canin Ultamino (proteins from feathers)
Tx of food allergyAvoid allergen
Steroids (poor response to pred: ddx food allergy, scabies, flea allergy)
+/-Apoquel or Cytopoint
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