10 Most common Veterinary Medical Conditions :Most common presenting clinical signs of Allergy symptoms Top 1: Skin diseases
Affects on Pet and Owner Relationship: Poor quality of life to pets with allergy disease
- Painful ears
- Renders relationship between owner and pet
- Worse physical function
- Active disease
- Fatigue
- Poor sleep
- Moody
- Itching becomes very obvious
Much later on you see kidney and liver failure. Do not assume all itchy pets are environmentally allergic there are other underlying etiologies.
In a private practise there is no good diagnostic testing for food allergies and it is one of the main contributors to itch.
It's better to excel in the outcome vs. promote the entire resolve on a medication as some may not work or may cause other issues with long-term use for certain pets.
Follow-ups in veterinary dermatology is extremely important a lot of things come into play overtime even though it initially responded to that therapeutic regimen.
70% of diagnosis of skin disease is actually related to the historical evaluation over environmental allergies.
Pets less then a year of age of onset allergies tend to be more food related, what that means is whenever they start with the clinical onset beyond six years of age having been in their same environment that pushes us more towards FOOD ALLERGY. Why? We're feeding the food day in and day out no matter the season.
Flavours which pets may ingest might actually elicit or worsen an allergic response, so we can see some seasonality association with that.
ORAL ALLERGY SYNDROM
- When a pet eats certain fruits and vegetables at that time of the year when those fruits and vegetables contain the same pollen and antigen that are emerging then you will also see a Cross Allergy Effect (Seasonality associated with the allergic disease). With food allergies depending on what system is triggered gut or skin you will notice Inflammatory Bowel Disease at the same time.
Since the triggers are being given day in and day out the food allergies actually surmount the effects of allergy treatments (Steroids, Immunosuppressant, Anti-inflammatory meds).
What this means is you can give the medication and yes, it will help decrease the inflammation, but because the antigen is being given everyday of their lives it pushes them over the effect of those medication, so you see pets being less responsive to treatment resulting in chronic recurrent bacterial folliculitis. The pet's not necessarily licking, chewing, scratching yet, but the upset balance of the immune system allows for secondary infection to erupt.
Combination Patients:
Every pet has a threshold for allergic reactions. Below this threshold, the immune system doesn’t overreact, and the pet seems fine. Above the threshold, clinical signs like itching, redness, or inflammation appear.
Food Allergies
A pet may be consuming an allergen (e.g., chicken, beef, soy, fruit, vegetable, grain) regularly but not enough to trigger obvious signs. The pet is “under the radar” of their allergic threshold.
Environmental Allergies (Atopy)
Seasonal allergens like pollen, dust mites, or mold increase immune activation.
When combined with existing low-level food allergens, the cumulative immune stimulus can push the pet over the threshold, triggering visible reactions.
Clinical Patterns You May See
Seasonal peaks: Itching or dermatitis flares during pollen seasons, even if the diet hasn’t changed.
Year-round mild itching with seasonal exacerbations: A pet has a baseline level of discomfort from chronic food allergens, worsened when environmental triggers spike.
Management Considerations
Strict elimination diet trials to rule in/out food allergens.
Environmental control measures during high pollen/mold seasons.
Anti-pruritic therapy (e.g., oclacitinib, lokivetmab, antihistamines) for peak seasons.
Combination approach is often needed for pets showing this overlapping pattern.
If your pet is experiences Chronic recurrent otitis externa as the only clinical sign which happens in
24 % food related allergies, it is a significant indication. You don't have to see all three areas and the back in every dog, effects can be local or regional.
With environmental allergic dogs the antigenic load is not high enough unless there is the addition of a food allergen.
This is the classic antigen antibody complex that basically makes its way through the limbs, starts plugging holes into the blood vessels and then you get necrosis beyond where the antigen antibody complex deposits.
Traditional Classification (Back in the Day)
Type I Hypersensitivity
- Immediate, IgE-mediated.
- Classical “allergies” like atopy, pollen, dust mites, molds.
- Rapid onset of pruritus, redness, hives.
Type II Hypersensitivity
- Antibody-mediated cytotoxic reactions.
- Rarely associated with typical “allergic” skin disease in pets.
Modern Understanding
Type I – Environmental/atopic triggers (IgE-mediated) remain central.
Type III – Immune complex-mediated/ Immune Complex Deposition(e.g., some food allergies).
Chronic exposure to food allergens can lead to immune complex deposition in skin, GI, or other tissues.
Type IV (delayed-type hypersensitivity, sometimes called Type IIII in older texts)
T-cell mediated, slower onset, can contribute to chronic dermatitis.
Often overlaps with both food and environmental allergies.
Key Clinical Insight
Food allergies can lower the allergic threshold and make pets more sensitive to environmental triggers.
Combination reactions are common: A pet may have mild food allergies year-round, which alone don’t cause severe signs, but when environmental allergens rise seasonally, the cumulative effect pushes the pet over the threshold, producing flares.
Immune Complex Deposition (Type III Hypersensitivity)
Antigens (e.g., food proteins) combine with antibodies (usually IgG or IgM) to form immune complexes.
Normally, these complexes are cleared by the immune system. If they accumulate, they can deposit in tissues such as the skin, kidneys, or blood vessels.
Deposited complexes activate complement and recruit inflammatory cells, causing tissue damage.
In skin: this can manifest as chronic pruritus, redness, or secondary infections.
In other organs: may cause glomerulonephritis (kidneys), vasculitis, or arthropathy.
Relation to Food Allergies
Certain food allergens can drive immune complex formation. Chronic low-level exposure may not trigger immediate itching, but over time can contribute to subclinical inflammation.
When combined with environmental allergens, the total immune activation can exceed the allergic threshold, producing flares.
**Key Point
Type I (IgE-mediated) reactions are fast and immediate.
Type III (immune complex-mediated) reactions are often slower, chronic, and cumulative, making them harder to detect without careful dietary and environmental management.
Emerging Hypersensitivity Types (V, VI, VII)
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Type V, VI, VII Hypersensitivities
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Type V: Often associated with autoantibody-mediated activation of cell receptors (e.g., some pemphigus variants).
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Type VI: Can involve chronic inflammation mediated by immune dysregulation, manifesting as chronic pruritus, chewing, scratching, vomiting, diarrhea, or acrylic granulomas.
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Type VII: Tied to broader immune-mediated disorders, including behavioral disorders, pemphigus, or systemic immune-mediated diseases.
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These types often overlap with classical I–III mechanisms but are recognized for their complex, chronic, or systemic presentations.
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Antigen-Antibody Complexes in Cats (Example: Penile Vasculitis)
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Pathophysiology:
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Environmental or food antigens trigger immune complex formation (IgG or IgM bound to antigen).
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Complexes deposit in small blood vessels, particularly in distal extremities (limbs, penile tissue).
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Deposition activates complement, attracts neutrophils, and leads to vascular plugging.
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Result: ischemia, necrosis, and tissue damage beyond the site of deposition.
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Clinical Signs:
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In cats, penile vasculitis is a classic manifestation.
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Can also occur in limbs, ears, or tail.
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Often associated with itching, inflammation, secondary infections, or systemic immune signs.
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Key Takeaways
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Chronic food or environmental allergens can contribute to multiple hypersensitivity mechanisms simultaneously.
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Type V–VII hypersensitivities explain more complex or chronic allergic presentations that were poorly understood in the classical system.
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Recognition of immune complex–mediated vascular injury (e.g., penile vasculitis) highlights the systemic impact of allergies, not just skin or GI signs.
Type III (immune complex-mediated) reactions are often slower, chronic, and cumulative, making them harder to detect without careful dietary and environmental management.
Classic pattern of barrier dysfunction and localized hypersensitivity reactions (happens in both veterinary and human dermatology)
1. Predilection Sites
Ventral body: Limbs, paws, inguinal region, axillae.
Frictional surfaces: Areas with constant rubbing or moisture (armpits, inner thighs, paw pads).
These areas are prone to microtrauma that compromises the epidermal barrier.
2. Barrier Dysfunction and Antigen Penetration
The epidermal barrier normally prevents allergens and microbes from penetrating the skin.
Friction, moisture, or minor trauma can create micro fissures, allowing antigens to bypass the barrier.
Once absorbed, antigens are presented to the immune system, triggering localized Type I (IgE-mediated) or Type III (immune complex-mediated) reactions.
3. Clinical Signs
Mild or chronic pruritus localized to affected areas.
Erythema, alopecia, excoriations from scratching or licking.
Sometimes secondary infections due to barrier compromise.
In humans, similar patterns are seen in eczema or atopic dermatitis at flexural surfaces.
4. Clinical Implications
Areas under constant friction or moisture are hotspots for allergic flares.
Repeated barrier damage can lead to chronic inflammation, perpetuating the allergic cycle.
Management may include:
Environmental or dietary allergen control.
Barrier repair (medicated shampoos, medicated creams).
Anti-pruritic therapy during flares.
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