Allergic Skin Disease

Question 1

Define hypersensitivity disease

Answer 1

Objectively reproducible signs due to exposure to a defined stimulus at a dose tolerated by normal individuals with NO ALLERGIC IMMUNOLOGIC mechanism or UNKNOWN mechanism

Question 2

Define allergic disease

Answer 2

Objectively reproducible signs due to exposure to a defined stimulus at a dose tolerated by normal individuals initiated by IMMUNOLOGIC HYPERSENSITIVITY due to a state of heightened reactivity to antigen or specific immunological mechanisms

Question 3

What is allergic disease?

Answer 3

Reaction to a normally innocuous non-self antigen and the allergic inflammation produces a tissue injury and can be induced or aggravated by non-immunological factors

Question 4

What are some examples of hypersensitivity/allergic skin disease?

Answer 4

Urticaria/angioedema (syndrome)
'Food allergy'
Contact allergy/dermatitis
Atopic dermatitis
Insect sting/bite hypersensitivities

Question 5

Define utricaria

Answer 5

Multiple wheals (hives)
Circumscribed raised lesions caused by dermal oedema

Question 6

Define angioedema

Answer 6

Marked localised subcutaneous oedema

Question 7

What is the pathomechanism of urticaria/angioedema?

Answer 7

Mast cell is the principle effector cell

Mast cell activation can be IgE dependent (type 1 allergy) or IgE independent (complement activation/non-immunological)

Question 8

What are the clinical characteristics of urticaria/angioedema?

Answer 8

Acute, recurrent, chronic, seasonalnon-seasonal, may progress to crusting/sloughing, variable pruritis

Question 9

What are some possible triggers for urticaria/angioedema?

Answer 9

Administered/applied substances, infections, parasitis infestation, insect bites/stings, dietary components, aeroallergens, contact allergens, other environmental substances, systemic disease, physical stimuli, hereditary condistion, auto-antibodies, idiopathic

Question 10

How is urticaria/angioedema diagnosed?

Answer 10

Avoidance and re-challenge ideally blinded and placebo controlled
For IgE mediated disease demonstration of allergen-specific IgE

Question 11

What are the possible immunological adverse reactions to food?

Answer 11

IgE mediated food allergy

Non-IgE mediated food allergy

Question 12

What are the possible non-immunological adverse reactions to food?

Answer 12

Idiosyncratic
Pharmacological
Metabolic

Question 13

What are the possible clinical signs of food intolerance and allergy?

Answer 13

Gastroenteritis, enteropathy

Urticaria, angioedema, pruritic skin disease

Question 14

How is food hypersensitivity/allergy diagnosed?

Answer 14

History and signs, response to restricted diet and relapse on old diet
Intra-dermal and serological tests of no benefit

Question 15

How is food hypersensitivity managed?

Answer 15

Allergen avoidance, treat secondary complications, glucocorticoids if allergen avoidance isn’t possible

Question 16

What is the aetiology of atopic dermatitis?

Answer 16

Genetics = skin barrier, IgE response, (skin) immune system
Environmental factors = reduced skin barrier, allergen exposure, typre of early immune stimulation (puppy/kitten), other factors?

Question 17

What is the pathophysiology of atopic dermatitis?

Answer 17

IMAGE

Question 18

What is the typical history of atopic dermatitis?

Answer 18

Age of onset 6mths- 3yrs, pruritis, rashes, ear infections

Time course can be seasonal, non-seasonal, non-seasonal with seasonal exacerbation, intermittent

Question 19

What primary skin lesions are seen with atopic dermatitis?

Answer 19

None, erythema, erythematous maculopapular rash

Question 20

What is the distribution of itch and lesions of atopic dermatitis?

Answer 20

Ears, face, armpits, feet, ventral abdomen, gluteals and hamstrings
Breed specific distributions

Question 21

What is the pathology of skin and ear disease with atopic dermatitis?

Answer 21

Immunological derangement leads to cutaneous abnormalities in skin barrier so Staph pseudintermedius and Malassezia pachydermatis can infect causing skin lesions exacerbating pruritis

Question 22

How is atopic dermatitis diagnosed?

Answer 22

Rule out/resolve other pruritic disease
5 of following criteria present = < 3 at onset, mostly indoor, corticosteroid responsive pruritis, chronic/recurrent yeast infections, affected front feet, affected pinnae, non-affected ear margins, non-affected dorso-lumbar area

Question 23

What is the treatment aim of atopic dermatitis?

Answer 23

Reduce pruritis to acceptable level with long-term control as safely as possible

Question 24

How is control of atopic dermatitis achieved quickest?

Answer 24

Addressing as many trigger factors as possible through combination of treatment modalities requiring a custom-tailored treatment plan