Allergy and the skin

Question 1

What is the most common presentation of an allergy?

Answer 1

Urticaria

Question 2

What is urticaria?

Answer 2

Very itchy erythematous lesions

“hives/wheals/nettle rash”

Question 3

When does urticaria appear and how long does it last?

Answer 3

Lesions appear within one hour

last 2-6 hours, sometimes 24 hours

Question 4

What is angioedema?

Answer 4

• Localised swelling of subcutaneous tissue or mucous membrane
• non-pitting oedema
• not itchy (unless associated with urticaria)

Question 5

What respiratory symptoms can allergy produce?

Answer 5

wheezing
nasal itching
sneezing
rhinorrhoea

Question 6

Give some symptoms of anaphylaxis.

Answer 6

• itchy skin or a raised, red skin rash (hives)
• swollen eyes, lips, hands and feet (angioedema)
• feeling lightheaded or faint.
• narrowing of the airways (wheezing and breathing difficulties)
• abdo pain, nausea and vomiting.
• collapse and unconsciousness.

Question 7

What investigations can be done for an allergy?

Answer 7

HISTORY
Specific IgE (RAST)
Skin prick 
Patch test 
Challenge test 
Serum mast cell tryptase level

Question 8

What is the risk of anaphylaxis in a skin prick test?

Answer 8

1:3000

Question 9

When is a challenge test used?

Answer 9

Only if skin prick test negative and history is strongly suggestive

Question 10

How is an allergy managed?

Answer 10

• allergen avoidance
• anti-histamines
• anti-inflam corticosteroid
• adrenaline autoinjector
• mast cell stabilisers
• immunotherapy

Question 11

what dose of antihistamine should be given during an allergic reaction?

Answer 11

Double the standard treatment should be enough. If not then seek medical attention

Question 12

What are the doses of adrenaline autoinjectors?

Answer 12

300µg adults

150µg children

Question 13

How long should be left before administering a second adrenaline autoinjector?

Answer 13

5-10 mins

Question 14

What is a type 4 allergy?

Answer 14

delayed type hypersensitivity
T cell mediated
onset of reaction typically after 24-48 hours

Question 15

What is a type 1 allergy?

Answer 15

IgE mediated hypersensitivity

Question 16

Give some examples of causes of contact allergic dermatitis?

Answer 16

Preservatives in cosmetics
rubber accelarators 
plants 
tattoo ink 
fragrances

Question 17

Which test is used for allergic contact dermatitis?

Answer 17

Patch testing

Question 18

When are the Finn chambers removed and when are the readings taken during patch testing?

Answer 18

Removed after 48 hours

Readings at 48 and 96 hours

Question 19

What is irritant contact dermatitis?

Answer 19

Non-immunological process
Contact with agents that abrade, irritate and traumatize skin directly
Does not require prior sensitization
Pattern depends on exposure

Question 20

Define allergy?

Answer 20

Allergy is a hypersensitivity disorder causing an exaggerated immune response to normally harmless substances in the environment