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Allergies and Drug Reactions 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?

25
When is the onset of a type IV reaction?
24-48 hours
26
What is the gold standard test for a type IV hypersensitivity reaction?
Patch testing
27
How long are the allergens left on for before testing a patch test?
48 hours
28
When are the results from a patch test tested?
48 and 96 hours
29
What type of reaction is irritant contact dermatitis?
Not an immune reaction
30
Does irritant contact dermatitis require prior sensitisation?
No
31
Which type of drug reactions are dose dependent? What does this mean?
Non-immunologically mediated- it means the reaction will get worse the more of the drug you have
32
What is the most common type of drug reaction?
Exanthamous
33
What are the symptoms of a non-immunologically mediated drug reaction?
Mainly rash; may also be pigment changes, itch/pain, photosensitivity
34
When pain occurs in a drug reaction, what does this imply?
Quite a serious reaction
35
When will the rash from a drug reaction withdraw?
When the drug is stopped
36
What are some very common drugs to cause reactions?
Beta lactams and NSAIDs
37
What are some risk factors for drug reactions?
Young adult, female, viral infections, CF, immunosuppressed
38
What are 5 drugs which are associated with exanthematous drug reactions?
Penicillin, erythromycin, allopurinol, NSAIDs, chloramphenicol
39
What type of reaction are exanthematous reactions (usually)?
Type IV
40
What is the onset of an exanthematous reaction?
4-21 days after taking the drug
41
How will the rash of an exanthematous drug reaction look?
Widespread and symmetrical
42
What are some other features of an exanthematous drug reaction which may or may not be present?
Itch and fever
43
Involvement of where in an exanthematous drug reaction usually implies something more serious?
Mucosal membranes
44
What are some indicators of a potential severe reaction?
Mucous membrane involvement and face, fever, lymphadenopathy, SOB and wheezing
45
Urticarial drug reactions are usually what type? Mediated by what?
Type 1 IgE
46
Describe the two types of urticarial drug reactions?
IgE mediated after re-challenge with drug or direct release of inflammatory mediators from mast cells on first exposure
47
How will fixed drug eruptions look?
Well formed, round plaques which are red and painful
48
Where do fixed drug eruptions occur?
Hands, genitals, lips, oral mucosa
49
Do fixed drug eruptions involve one or more lesions?
Usually restricted to a single lesion, if it re-occurs this will also appear at the same site
50
Give two examples of severe cutaneous adverse reactions?
Stevens Johnsons Syndrome and Toxic Epidermal Necrolysis
51
What are the acute problems in a phototoxic drug eruption?
Skin toxicity
52
What are the chronic problems in a phototoxic drug eruption?
Pigment changes, photo aging, photocarcinogenesis
53
Are phototoxic drug reactions immunological?
No
54
Which types of light cause phototoxic drug reactions?
UVA and visible light
55
History and examination are usually sufficient to treat phototoxic drug eruptions. If extra investigations are needed, what can be used?
Phototesting or biopsies
56
Which patients are more likely to suffer from cutaneous drug eruptions?
Immunocompromised
57
What drugs can cause acne?
Steroids, androgens, lithium, isoniazid, amiodarone
58
What drugs can cause drug induced bullous pemphigoid?
ACE inhibitors, penicillin, furosemide
59
What drug causes linear IgA disease?
Vancomycin

Dermatology (15 decks)

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