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Dermatology > Allergies and Drug Reactions > Flashcards

Allergies and Drug Reactions Flashcards

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Dermatology Board Prep flashcards
1
Q

When do allergic reactions occur?

A

When a person’s immune system overreacts to a normally harmless substance

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2
Q

What is hypersensitivity?

A

An immune reaction which causes damage to self

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3
Q

What are the main hypersensitivity reactions that involve the skin?

A

Type I and type IV

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4
Q

Which type of hypersensitivity can result in anaphylaxis?

A

Type 1

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5
Q

Describe urticaria?

A

Very itchy lesions which appear in 1 hour- can last up to 24 hours

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6
Q

Describe type 1 hypersensitivity?

A

The antigen induces cross linking of IgE bound to mast cells and basophils, with release of vasoactive mediators

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7
Q

How quickly do type 1 hypersensitivity reactions occur?

A

Within minutes and up to 2 hours

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8
Q

How can a person be exposed to an allergen?

A

Contact, inhalation, ingestion, injection

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9
Q

In type 1 reactions, must the history be consistent with every reaction?

A

Yes

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10
Q

Describe angioedema?

A

Localised swelling of subcutaneous tissue or mucous membranes, not usually itchy and associated with non-pitting oedema

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11
Q

What are some features of a clinical presentation of a type 1 reaction?

A

Urticaria, angioedema, wheezing/asthma, anaphylaxis

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12
Q

What are some investigations for type 1 hypersensitivity?

A

Specific IgE test (RAST), skin prick testing, challenge testing

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13
Q

What must you do while performing a challenge test?

A

Monitor vital signs

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14
Q

When should a challenge test be done?

A

Only if the skin prick test is negative

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15
Q

What test can be done during anaphylaxis?

A

Serum mast cell tryptase levels

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16
Q

How do you manage type 1 allergy?

A

Allergen avoidance, anti-histamines, steroids, adrenaline, mast cell stabilisers, immunotherapy

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17
Q

How much adrenaline should an auto injector for adults and children?

A

Adults = 300micrograms, children = 150micrograms

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18
Q

How many adrenaline auto injectors should patients with type 1 allergy be given?

A

2

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19
Q

Anaphylaxis is a life threatening reaction which is usually characterised by what?

A

Rapidly developing symptoms involving the airway (pharynx/larynx oedema), breathing (bronchospasm) and circulation (hypotension, tachycardia)

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20
Q

Give some examples of reactions which are not allergic?

A

Not mediated by IgE, direct mast cell degranulation, metabolic, toxins

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21
Q

Give two drugs which can cause direct mast cell degranulation?

A

Morphine, NSAIDs

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22
Q

Give an example of a metabolic non-immune mediated reaction?

A

Lactose intolerance

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23
Q

Describe type IV hypersensitivity?

A

Sensitised Th1 cells release cytokines which activate macrophages and CD8+ T cells to mediate cellular damage

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24
Q

What type of reaction is allergic contact dermatitis?

A

Type IV

25
Q

When is the onset of a type IV reaction?

A

24-48 hours

26
Q

What is the gold standard test for a type IV hypersensitivity reaction?

A

Patch testing

27
Q

How long are the allergens left on for before testing a patch test?

A

48 hours

28
Q

When are the results from a patch test tested?

A

48 and 96 hours

29
Q

What type of reaction is irritant contact dermatitis?

A

Not an immune reaction

30
Q

Does irritant contact dermatitis require prior sensitisation?

A

No

31
Q

Which type of drug reactions are dose dependent? What does this mean?

A

Non-immunologically mediated- it means the reaction will get worse the more of the drug you have

32
Q

What is the most common type of drug reaction?

A

Exanthamous

33
Q

What are the symptoms of a non-immunologically mediated drug reaction?

A

Mainly rash; may also be pigment changes, itch/pain, photosensitivity

34
Q

When pain occurs in a drug reaction, what does this imply?

A

Quite a serious reaction

35
Q

When will the rash from a drug reaction withdraw?

A

When the drug is stopped

36
Q

What are some very common drugs to cause reactions?

A

Beta lactams and NSAIDs

37
Q

What are some risk factors for drug reactions?

A

Young adult, female, viral infections, CF, immunosuppressed

38
Q

What are 5 drugs which are associated with exanthematous drug reactions?

A

Penicillin, erythromycin, allopurinol, NSAIDs, chloramphenicol

39
Q

What type of reaction are exanthematous reactions (usually)?

A

Type IV

40
Q

What is the onset of an exanthematous reaction?

A

4-21 days after taking the drug

41
Q

How will the rash of an exanthematous drug reaction look?

A

Widespread and symmetrical

42
Q

What are some other features of an exanthematous drug reaction which may or may not be present?

A

Itch and fever

43
Q

Involvement of where in an exanthematous drug reaction usually implies something more serious?

A

Mucosal membranes

44
Q

What are some indicators of a potential severe reaction?

A

Mucous membrane involvement and face, fever, lymphadenopathy, SOB and wheezing

45
Q

Urticarial drug reactions are usually what type? Mediated by what?

A

Type 1 IgE

46
Q

Describe the two types of urticarial drug reactions?

A

IgE mediated after re-challenge with drug or direct release of inflammatory mediators from mast cells on first exposure

47
Q

How will fixed drug eruptions look?

A

Well formed, round plaques which are red and painful

48
Q

Where do fixed drug eruptions occur?

A

Hands, genitals, lips, oral mucosa

49
Q

Do fixed drug eruptions involve one or more lesions?

A

Usually restricted to a single lesion, if it re-occurs this will also appear at the same site

50
Q

Give two examples of severe cutaneous adverse reactions?

A

Stevens Johnsons Syndrome and Toxic Epidermal Necrolysis

51
Q

What are the acute problems in a phototoxic drug eruption?

A

Skin toxicity

52
Q

What are the chronic problems in a phototoxic drug eruption?

A

Pigment changes, photo aging, photocarcinogenesis

53
Q

Are phototoxic drug reactions immunological?

A

No

54
Q

Which types of light cause phototoxic drug reactions?

A

UVA and visible light

55
Q

History and examination are usually sufficient to treat phototoxic drug eruptions. If extra investigations are needed, what can be used?

A

Phototesting or biopsies

56
Q

Which patients are more likely to suffer from cutaneous drug eruptions?

A

Immunocompromised

57
Q

What drugs can cause acne?

A

Steroids, androgens, lithium, isoniazid, amiodarone

58
Q

What drugs can cause drug induced bullous pemphigoid?

A

ACE inhibitors, penicillin, furosemide

59
Q

What drug causes linear IgA disease?

A

Vancomycin

Dermatology (15 decks)

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