Allergic skin disease Flashcards Preview

Dermatology > Allergic skin disease > Flashcards

Flashcards in Allergic skin disease Deck (71):
1

definition of contact dermatitis

inflammation of the skin caused by direct contact with an irritating or allergy-causing substance

2

irritant

irritating substance, eg acid, base, chemicals, metal salt etc.

3

allergen

allergy-causing substance, eg dye, oil, chemical used for fabrics, rubbers, cosmetics etc.

4

classification of contact dermatitis

irritant, allergic

5

irritant contact dermatitis

inflammatory reaction in the skin resulting from exposure to a substance that causes an eruption in most people who come into contact with it

6

allergic contact dermatitis

acquired sensitivity to various substances that produce inflammatory reactions in those, and only those, who have been previously exposed to the allergen

7

how to recognize contact dermatitis caused by acid?

brownish scab, beneath which is an ulceration that heals slowly

8

how to recognize contact dermatitis caused by pesticides?

large bullae, erythema

9

bromhydrosis

underarm odor

10

what is bromhydrosis caused by?

bacterial decomposition of apocrine sweat, producing fatty acids with distinctive offensive odors

11

give an example for chronic allergic contact dermatitis

lichenification caused by metal clasps

12

give an example for an allergen causing subacute allergic contact dermatitis

metal in a metal buckle

13

what may cause acute allergic contact dermatitis?

plants

14

which plants may cause contact dermatitis?
name 2 examples

many, including trees, grasses, flowers, vegetables, fruits, and weeds
ex: poison ivy, mango

15

which allergen may cause allergic contact dermatitis in women?

cosmetics

16

what allergen may cause edema in the foreskin?

drugs

17

what are the differences between irritant dermatitis and allergic contact dermatitis? (6)

irritant dermatitis:
- acids, alkalis
- burning reaction
- pain
- everyone's affected
- no latent period
- do not use patch test!

allergic contact dermatitis:
- various substances
- allergic reaction
- itching
- only some people affected
- latent period
- patch test positive

18

latent period

delay between exposure to a disease-causing agent and appearance of manifestations of the disease. interval between exposure to an infectious organism or carcinogen and the clinical appearance of disease.

19

give 2 examples for "latent period"

after exposure to radiation, there is a latent period of 5 years, on average, before development of leukemia, and more than 20 years before development of other malignant conditions.

HIV -- latent period -- AIDS

20

what happens during the latent period of allergic contact dermatitis?

1) first exposure
2) skin sensitization
3) hypersensitivity develops
4) exposure (light is sufficient)
5) outbreak

21

how is the patch test performed in allergic contact dermatitis?

a piece of blotting paper is soaked with suspected allergen, taped to skin for 24 to 48 h
if rash develops, the test is positive

22

when does reevaluation need to be done after the patch test in allergic contact dermatitis?

2 days, and again on day 4 or 5, because a positive reaction may not occur earlier

23

allergy skin prick test

- one of the most common methods of allergy testing
- small amount of suspected allergen is placed on skin (usually forearm, upper arm or back)
- skin is pricked to transfer the allergen to the area under skin surface
- close observation for signs of reaction (eg swelling, redness)
- several suspected allergens can be tested simultaneously
- result is obtained within 20 minutes

24

clinical manifestations of contact dermatitis

- contact spots with clear boundaries
- erythema or blisters
- itching or pain
- course: 1-2 weeks
- long-term repeated contact: lichenification

25

what is the diagnosis of contact dermatitis based on?

1. contact history
2. clinical manifestations
3. patch test

26

which treatments does contact dermatitis involve generally?

1. get rid of suspected allergen or irritant
2. local treatment
3. systemic treatment: antihistamines, calcium, vitamin C, corticosteroids

27

treatment of choice for acute dermatitis?

wet compresses of solution

28

what is the treatment of choice for eruptions that are limited?

topical corticosteroid cream (superior to any other local application)

29

definition of drug eruption

an adverse cutaneous reaction produced by ingestion, parenteral use, or local application of a drug, which may produce various morphologic patterns and types of lesions, also called drug rash

30

drug eruptions are most commonly caused by which drugs? (6)

- antibiotics
- NSAIDS
- sulfa drugs
- sedatives
- blood serum and antitoxin
- TCM drugs

31

pathogenesis of drug eruptions

1) allergic reaction (most)
2) non-allergic reaction (few)
- may result from normal pharmacological effects of a drug, eg urticaria worsens with aspirin intake

32

features of allergic drug eruptions (6)

- occurs in a few individuals
- not related to a drug's pharmacological action and dosage
- latent period is commonly 4-20 days
- multiple lesions
- cross-reaction
- corticosteroids are effective

33

cross-reaction definition and example

a patient is sensitive to drug A, drug B is similar to drug A in chemical structure --> patient is also sensitive to drug B
Ex: a patient allergic to penicillin should not use cephalosporin due to risk of cross-reaction - consult department of infectious diseases for alternative drugs

34

classification of clinical manifestations of drug eruptions

mild drug rash and severe drug eruption

35

manifestations of mild drug rash

- fixed drug eruption
- urticarial drug eruption
- exanthems
- erythema multiforme
- purpuric drug eruption

36

erythema multiforme

- peripheral ring of erythema
- flatter, more purpuric, and duskier towards the center
- iris or target-like looking lesion

37

manifestations of severe drug eruption

- exfoliative dermatitis
- drug-induced bullosa epidermolysis
- serious erythema multiforme drug eruption

38

how to diagnose drug eruptions?

- history of taking medicine
- latent period
- lesions appearing abruptly
- positive drug test

39

how to treat drug eruptions?

- stop using suspected drug/s
- local treatment
- systemic treatment

40

systemic treatment of drug eruptions includes...

- corticosteroids
- calcium
- antihistamines
- supportive treatment
- antibiotics

41

definition of urticaria

itchy, swollen, red wheals or patches on the skin that appear suddenly as a result of the body's adverse reaction to certain allergens. it can appear anywhere, including the face, lips, tongue, throat or ears. varies in size and can last for minutes or hours

42

what is urticaria also called?

hives

43

definition of angioedema

- swelling similar to urticaria (hives), but occurs beneath the skin instead of on surface
- characterized by deep swelling of eyes, lips and sometimes scrotum (the most distensible tissues)

44

what is angioedema also called?

giant urticaria

45

how frequent is urticaria?

extremely common

46

how much percent of the population experience urticaria at some point in life?

15-25 %

47

how much percent of the population will experience urticaria alone?

40 %

48

how much percent of the population will experience angioedema alone?

10 %

49

how much percent of the population will experience urticaria and angioedema at the same time?

50 %

50

classification of urticaria

acute, chronic

51

acute urticaria

- evolves over days to weeks
- individual wheals last less than 24 h
- resolution within 6 weeks of onset

52

chronic urticaria

daily episodes of urticaria lasting longer than 6 weeks

53

etiology of urticaria

allergic triggers

54

allergic triggers of acute urticaria

- drugs
- food
- food additives
- viral infections: hepatitis ABC, EBV
- insect bites and stings
- contactants and inhalants (including animal tander and latex)

55

allergic triggers of chronic urticaria

- physical factors: cold, heat, dermatographic, pressure, solar
- idiopathic: 75 % of triggers unclear

56

primary effector cell in urticarial reactions?

mast cell

57

pathogenesis of urticaria

1. release of histamine from mast cells situated around capillaries
2. increased capillary permeability, small vessel dilatation -> extravasation of fluid and proteins
3. urticarial wheal formation

58

clinical manifestations of acute urticaria

- wheals, erythema
- duration: minutes to hours
- sudden onset and sudden disappearance
- no remaining skin changes after disappearance of lesions

59

clinical manifestations of severe cases of urticaria

accompanying syndromes, some being life-threatening, such as:
- respiratory: dyspnea
- GI tract: nausea, vomiting, abdominal pain
- cardiovascular system: hypotension
- edema on the skin, mucus membranes, GI tract, along with small vessel dilatation

60

duration of chronic urticaria

at least 6 weeks

61

dermatographia

sharply localized edema or wheal with surrounding erythematous flare occuring after seconds to minutes after the skin has been stroked

62

what is dermatographia also called?

factitious urticaria

63

what is the diagnosis of urticaria based on? (4)

1. wheals, erythema
2. sudden onset and disappearance
3. itching
4. recurrence

64

pharmacological options for urticaria

- antihistamines
- corticosteroids
- calcium, vitamin c
- local treatment

65

antihistamines used for the treatment of urticaria (4)

- 1st generation H1 blockers
- 2nd generation H1 blockers
- tricyclic antidepressants (eg doxepin)
- combined H1 and H2 blockers

66

when should corticosteroids used for the treatment of urticaria? what should be avoided?

- severe acute urticaria
- long-term use

67

what type of solution is used to administer calcium for urticaria?

10 % calcium gluconate solution

68

mechanism of action of vitamin c and calcium

reduce capillary permeability

69

local treatment options

lotion containing menthol, phenol, and camphor has an antipruritic effect

70

pros and cons of 1st generation H1 blockers (diphenhydramine, hydroxyzine) for uritcaria and angioedema?

pros: rapid onset of action, inexpensive
cons: sedating, anticholinergic

71

pros and cons of 2nd generation H1 blockers (astemizole, cetirizine, fexofenadine, loratadine)?

pros: no sedation (except cetirizine); no anticholinergic effects; bid and qd dosing: 10 mg
cons: QT prolongation, ventricular tachycardia (astemizole only) in a subgroup of patients