Allergy and the skin

Question 1

What is hypersensitivity?

Answer 1

An exaggerated immune response which causes damaged to oneself

Question 2

How can hypersensitivity be classified?

Answer 2

Type 1 - IgE mediated
Type 2 - IgG mediated cytotoxic
Type 3 - Immune complex mediated
Type 4 - Delayed cell mediated

Question 3

What are allergic reactions?

Answer 3

Immune system response to a normally harmless substance

Question 4

What is an allergen?

Answer 4

Substance which causes an immune reaction

Question 5

What is the theory behind the increasing prevalence of allergy?

Answer 5

Hygiene hypothesis

Question 6

What is the time frame of a type 1 allergic reaction?

Answer 6

Between minutes to two hours

Question 7

What routes of exposure can cause a type 1 allergic reaction?

Answer 7

Inhalation
Ingestion
Skin contact
Injection

Question 8

What is the main history feature of a type 1 allergic reaction?

Answer 8

Consistent reaction every time

Question 9

What are the common ingested allergens?

Answer 9

Nuts

Seafood

Question 10

What are the common inhaled allergens?

Answer 10

House dust mite

Pollen

Question 11

What are the common skin contact allergens?

Answer 11

Animal dander

Latex

Question 12

What are the common injected allergens?

Answer 12

Bee

Medication

Question 13

How does a type 1 allergic reaction present?

Answer 13

Urticaria
Angioedema
Wheezing/asthma
Anaphylaxis

Question 14

How does urticaria present?

Answer 14

Itchy
Wheals
Lasts 2-6 hours but less than 24 hours

Question 15

What is angioedema?

Answer 15

Swelling of the subcutaneous tissues or mucous membranes

Question 16

How does angioedema present?

Answer 16

Swelling
Not itchy
Non-pitting

Question 17

What is anaphylaxis?

Answer 17

Life threatening general or systemic hypersensitivity reaction

Question 18

How does anaphylaxis present?

Answer 18

Rapidly developing
Airway (oedema)
Breathing (tachypneoa)
Circulation (hypotension)
Associated skin/mucosal changes

Question 19

How is suspected type 1 hypersensitivity investigated?

Answer 19

Specific IgE (RAST)
Skin prick
Challenge test (rare)
Serum mast cell tryptase (during anaphylaxis)

Question 20

What are the benefits and drawbacks of skin prick testing?

Answer 20

Cheap
Quick
Specific
Sensitive

Small anaphylaxis risk

Question 21

When would challenge testing be undertaken?

Answer 21

Skin prick testing negative

Last resort

Question 22

How is type 1 allergy managed?

Answer 22

Avoidance
Anti-histamines
Corticosteroids (anti-inflammatory)
Adrenaline autoinjector (anaphylaxis)
Sodium chromoglycate 
Immunotherapy

Question 23

What is the dose of an adrenaline autoinjector in children and adults?

Answer 23

150ug

300ug

Question 24

How many adrenaline autoinjector pens should a patient have at the one time?

Answer 24

2

Question 25

Is coeliac an allergic condition?

Answer 25

No

Question 26

Is lactose intolerance an allergic condition?

Answer 26

No

Question 27

What is the timeframe for a type 4 hypersensitivity reaction?

Answer 27

Reaction occurs within 24-48 hours of exposure

Question 28

Is type 4 hypersensitivity specific to a particular antigen?

Answer 28

Yes

Question 29

Which type of cells are involved in type 4 hypersensitivity?

Answer 29

T cells

Question 30

What type of skin reaction is mediated by type 4 hypersensitivity?

Answer 30

Allergic contact dermatitis

Question 31

How do type 4 hypersensitivity skin reactions present?

Answer 31

Specific to allergen contact/exposure site/pattern | Mostly eczematous reaction

Question 32

How are type 4 hypersensitivity skin reactions investigated?

Answer 32

Patch testing

Question 33

How is a patch test carried out?

Answer 33

Allergens placed in wells Wells applied to back and removed after 48 hours Back is checked at 48 hours and 96 hours If photo-allergens are suspected two wells must be done one exposed to UV and one not

Question 34

What are the three main categories of dermatitis?

Answer 34

Atopic Irritant Allergic

Question 35

Is irritant contact dermatitis an immunologically mediated process?

Answer 35

No

Question 36

How does irritant contact dermatitis happen?

Answer 36

Skin comes into contact with something which directly irritates, abrades or traumatises it

Question 37

How does irritant contact dermatitis present?

Answer 37

Depends on the pattern of exposure

Question 38

Give two examples of irritant contact dermatitis

Answer 38

Lip lick dermatitis | Nappy rash

Question 39

What is atopic eczema associated with?

Answer 39

Asthma | Hayfever/allergic rhinitis

Question 40

How is atopic eczema distributed?

Answer 40

Flexural

Question 41

How is psorisasis distributed?

Answer 41

Extensor

Question 42

How is irritant dermatitis managed?

Answer 42

Avoidance or modification

Question 43

How is dermatitis treated?

Answer 43

Emollients Steroids UV phototherapy Immunosupressants