Topic 44 - Allergodermatitis (without atopy) Flashcards by Hege Osland

What are the different steps of a clinical approach in case of allergy dermatitis?

History
physical exam: ectoparasites, hair and skin, take pictures
Skin scrape: for microscopic examination
Blood exam
contact allergy - check for
Food allergy - check for
Allergy tests
skin biopsy

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Additional examination methods for dermatological patient:

Skin scraping
Skin biopsy
Cytology
Otoscpy
Flea comb
Intradermal skin test

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Most important problem(s) concerning a dermatological patient

Pruritus and alopecia

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Why is it important to have a diagnosis in case of allergy dermatitis?

If the animal has any ectoparasites, and we decide to treat for allergy with long-term cortisone, and without any antiparasitic drug - The cortisone will aid the sarcoptic overgrowth

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Definition of allergy:

Increased reactivity after meeting with a foreign body 2 or more times with the result of inflammation

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Name the terminology we use in regards to dermatology:

Atopy
Allergy
Pesudo-allergy
Idiosyncrasy
Allergen
Food allergen

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What is Atopy?

An exagerated immune response

genetic tendency to develop allergic diseases

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What is allergy?

Hypersensitivity of immunological origin

It is an exaggerated immune response to a foreign antigen

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What is pseudo allergy?

Hypersensitivity of non-immunological origin and non-specific sensitivity

Example: nettle sting (brennesle)

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What is Idiosyncrasy?

Hypersensitivity of non-immunological origin, but with increased sensitivity of the mast cells that contain histamine nad serotonin

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What is allergen?

Non-infectious, non-invasive and innocous antigen

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What is food allergen?

re almost always proteins although other food constituents, such as certain additives, are known to have allergenic properties

Example: heat, acid and protease stabile; water-soluble glycoproteins

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Name the levels of hypersensitivity reactions:

Anaphylaxis
Cytotoxic
Immuno-complex
Cell mediated

Hypersentiivy type 1-4

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For which type of disorder(s) do we use the hypersensitivt reaction levels?

Immune mediated disorders

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Definition of immune mediated disorder:

a condition that results from an abnormal immune system response

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Anaphylaxis

Which antibody reacts?
Reaction time?
Symptoms:

Antibody: IgE, IgG, antibody on cell surface

Reaction time: 1-15/20 min

Symptoms: Urticaria, allergic dermatitis, atopy, angioedema

Cytotoxic

Which antibody reacts?
Reaction time?
Name diseases:

Antibody: Complement binding IgG, IgM

Reaction time: 4-8 hours

Disease: Drugs, haemolytic anaemia, blood transfusion,

Immuno-complex

Which antibody reacts?
Reaction time?
Name diseases:

Antibody: Complement binding free IgG

Reaction time: 2-4-8 hours

Disease: Vasculitis, drugs, Systemic Lupus Erythematosus

Cell-mediated

Which antibody reacts?
Reaction time?
Name diseases:

Antibody: Antibody binds to T-lymphocyte

Reaction time: 24-72 hours

Disease: Allergy, contact allergy

Name diseases that are of allergic origin

Urticaria
Angiodema
Food hypersensitivity
Contact hypersensitivity
Drug eruption
Intestinal parasitic hypersensitivity
Hormonal hypersensitivity
Flea allergy dermatitis

Urticaria

Definition
Occurence, which species?
Causative agent

Definition: Cutaneous reaction to a immunological or non-immunological stimuli, also called = Hives

Occurence: Uncommon in dogs and cats

Causative agent: Vaccine, drugs, insect bite

Urticaria

Type of reaction:
Clinical signs:
Treatment:

Type of reaction: Type 1 and 3 hypersensitivty

Clinical signs:
1. Wheals
2. Bumps
3 hair “up” on lesions
4 Variable prurotus

Treatment:
- Allergen elimination
- antihistamines + glucocorticoids

Angiodema

Definition
Occurence, which species?
Causative agent

Definition: Oedematous swelling by vascular leakage into subcutis

Occurence, which species?: Dogs and cats

Causative agent: Bee, wasp stings

Angiodema

Type of reaction:
Clinical signs:
Treatment:

Type of reaction: Type 1 hypersensitivity

Clinical signs:
1. Extreme swelling of the face
2. Anaphylactics shock can develop

Treatment:
1. Adrenalin SCin case of anaphylactic shock
2. corticosteroids IV

**Food hypersesntivity** ## Footnote Definition Occurence, which species? Causative agent

*Definition:* Adverse reaction to a food or a food additive *Occurence, which species?:* Dog and cat *Causative agent:* Varies from dogs to cat, any food antigen can be allergenic if it reaches and stimulates allergy-associated immune cells ## Footnote Dog = chicken, turkey, beef, milk, Cat = chicken, turkey, beef, milk, fish

**Food hypersesntivity** ## Footnote Type of reaction: Clinical signs: Treatment:

*Type of reaction:* Type **1**, **2**, **3**, **4** hypersensitivity *Clinical signs:* Depending on species *Treatment:* - Alleregen avoidance - Hypoallergic diet for 2 months ## Footnote Clinical signs DOG: Pruritus, urticaria, seborrhea Clinical signs CAT: Generalised pruritus, miliary dermatitis

**Contact hypersensitivity** ## Footnote Definition Occurence, which species? Causative agent

*Definition:* Skin disease triggered by an exogenous agent *Occurence, which species?* Uncommon due to fur/coat protection *Causative agent:* Pollen, soap/shampoo, metal, rubber, plastic

**Contact hypersensitivity** ## Footnote Type of reaction: Clinical signs: Tests to diagnose: Treatment:

*Type of reaction:* Type **4** hypersensitivity *Clinical signs:* They appear after being in contact with the allergen for over 6 months Lesions: maculas, papulas, hyperpigmentations and possible pruritus *Tests to diagnose:* elimination and provocative exposure for 2 week or patch testing for 48 hours *Treatment:* Avoidance

Name the different types of contact hypersensitivity

Allergic contact dermatitis Irritant contact dermatitis

**Drug eruption** ## Footnote Definition Occurence, which species?

*Definition:* Cutaenous adverse drug reastion *Occurence, which species?* dogs and cats, bu very rare!

**Drug eruption** ## Footnote Clinical signs: Treatment:

*Clinical signs:* Mimimc any other skin disease, with variable skin lesions *Treatment:* Stop all drugs that may have caused lesions, and administer symptomatic treatment

Why are glucocorticoids not advised to use in case of drug eruption?

Because they have an effect on humoral and cell-mediated immunity ## Footnote = they may predispose secondary infections, sepsis, delayed healing and continued organ damage

**intestinal parasitic hypersensitivity** ## Footnote Definition: Occurence, which species? Type of reaction:

*Definition:* Reaction to parasites *Occurence, which species?* Dogs and cats, but very uncommon *Type of reaction:* Unknown, but may be type **1** hypersensitivity

**intestinal parasitic hypersensitivity** ## Footnote Clinical signs: Treatment:

*Clinical signs:* pruritic crusting papules or seborrhea may develop *Treatment:* Antiparasitic treatment

**Hormonal hypersensitivity** ## Footnote Definition: Occurence, which species? Causative agent(s): Type of reaction:

*Definition:* *Occurence, which species?* Moslty intact females, rare in dogs *Causative agent(s):* Progesterone, estrogen, testosterone *Type of reaction:* Might be related to type **1** or **4**

**Hormonal hypersensitivity** ## Footnote Clinical signs: Tests to diagnose: Treatment:

*Clinical signs:* * - Pruritus - Symmetrical lesions on face, feet and ears - Enlarged vulva and nipples - Irregular cycles - Pseudopregnancy *Tests to diagnose:* Intradermal testing with hormones *Treatment:* Spaying

**Flea allergy dermatitis** ## Footnote Definition: Occurence, which species? Type of reaction:

*Definition:* Hypersensitive reaction to antigens in the flea saliva *Occurence, which species?* Both cats and dogs, but more common in dogs *Type of reaction:* Type **1** and **4** immunological reaction which is seasonal ## Footnote Type 1 = immediate reaction Type 4 = delayed reaction

**Flea allergy dermatitis** ## Footnote Clinical signs: Treament:

*Clinical signs DOGS:* Typical localisation on the back, dorsal tail, inner thighs. We see: pruritus, papulas, seborrheic alopecia, pyoderma, lichenification *Clinical signs CATS:* No unique pattern, but we see pruritic miliary dermatitis *Treament:* Flea contol, topical therapy, anti-inflammatoies and might give corticosteroids for a short time