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Dermatology > allergic contact dermatitis > Flashcards

allergic contact dermatitis Flashcards

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Dermatology Board Prep flashcards
1
Q

define allergy

A

exaggerated reaction of immune system following contact with certain foreign substances

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2
Q

define allergen

A

Allergen: substance that causes or elicits the allergic reaction

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3
Q

Red, itchy, weepy patches of skin. Can occur in different conditions, including allergic contact, irritant contact and atopic dermatitis

A

eczema

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4
Q

What is allergic contact dermatitis?

A

An allergic reaction to something that comes in contact with the skin

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5
Q

who gets allergic contact dermatitis?

A

Potentially anyone Genetic predisposition

Atopy: tendency towards developing allergies, asthma, hay fever, dermatitis

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6
Q

How does allergic contact dermatitis happen?( two steps)

A

Two-step process
Becoming allergic (sensitization or induction)
Developing the rash after re-exposure (elicitation)

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7
Q

what is step 1 of allergic contact dermatitis? what can predispose to step 1?

A

Step 1: Becoming allergic

Sensitization: first contact
Must first contact an allergen to develop allergy
Certain conditions predispose to development of allergy
open skin: loss of barrier function

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8
Q

what is step 2 of allegic contact dermatitis?

A

Step 2: developing the rash

Once sensitized, immune system “remembers” allergy
When contact with allergen recurs (re-challenge), immune memory recalls allergy and sets allergic reaction in motion: elicitation

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9
Q

what are the sign and symtpoms of the rash of acute allergic contact dermatitis (4)

A

itchy
red
crusting / oozing
blisters

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10
Q

what are signs and symptoms of chronic allegic contact dermatitis?

A

Chronic allergic contact dermatitis
+/- itch
less red
hyperpigmentation( hall mark of inflammation in darker skinned ppl)

thickened skin
fewer blisters, may see more cracking

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11
Q

ACD usually affects skin __________ with allergen

A

ACD usually affects skin at site of contact with allergen

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12
Q

ACD is a ______reaction

When do symptoms develop?

with repeated exposure, describe the rxn?

how long does the rash last?

which symptoms are not present?(2)

A

ACD is a delayed-type hypersensitivity reaction

Symptoms develop 24-48+ hrs after exposure
With repeated exposure, reactions are quicker and more intense
Rash lasts 7-14 (or more) days
Usually **no hives, wheezing **

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13
Q

what in posion ivy causes ACD?

when does the rash appear? how long does it last?

what are the symtoms?

what is the pattern of the rash?

A

Allergic reaction to oil (urushiol) in plant

Rash appears 1-4 days after exposure
Lasts 7-21 days
Symptoms range from mild itch to severe itch with blisters
Linear pattern suggests “outside job”

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14
Q

Can posion ivy rash be spread in the blister fluid?

A

NO! Only contact with the oil will spread the rash

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15
Q

how can urushiol be spread?(3 ways)

A

Urushiol is present in vines and can be spread by contact, or in air by burning

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16
Q

what causes allegic contact dermatitis?

A

Usually **small molecular weight chemicals **

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17
Q

what are type of rxn are food and environmental allergens morel likely to cause? what are the symptoms for these?

A

Foods and environmental allergens (dust, molds, pets, etc) more likely to cause immediate-type hypersensitivity reactions

symptoms: sneezing, cough, hives

18
Q

common allergens: what are they?(6) where are they?

A

Nickel and other metals
Fragrances
Preservatives
Compounds in rubber products
Topical antibiotics (neomycin, bacitracin)
Plants

19
Q

nickel allergy: how common? where is expsoure most liely?

A

Nickel allergy one of most common allergies
Up to 15% in US
Incidence increasing
Exposure to nickel common in jewelry
Body piercing thought to contribute

20
Q

where is nickel most likely?

A

jewelry, metal objects ( paper clip, keys coins)

clothing: jean snaps, zippers, eyelets

medical devices including artificial joints, pacemaker

21
Q

which test is used to test for nickel in products?

A

Dimethylglyoxime test: pink color indicates presence of nickel

The dimethylglyoxime – ammonia test is able to detect nickel content in a metal object.

22
Q

some foods that contain nickel?

A

Cocoa & dark chocolate
Beer
Oatmeal
Oysters
Dry legumes
Asparagus
Hazelnuts
Sunflower seeds
Gelatin
Soybeans
Baking powder

note: nickel in some multivitamins

23
Q

recommendation for nickel allergy?

A

Avoid exposure to nickel-containing metals
Cover metals with plastic, etc.
If piercing, use non-nickel containing metals
Watch for reactions to other metals: cobalt, chromium
Low-nickel diet may benefit some, but not often recommended
Legislation to minimize nickel exposure in common items

24
Q

frangance allergies:

A

Allergies to fragrances common
Second most common allergy
Up to 10% patients in allergy clinics
Many different components of fragrances can cause allergy
Testing usually done in “mixes”
Can react both to natural and synthetic fragrances

25
Q

where are most fragrances found?

A

Most personal care products contain fragrances
perfumes, colognes
essential oils
household products (room fresheners, candles)
medicated creams, medicaments

note: unscented products have masking fragrances, even fragrance free products have traces of fragnaces if not used for that purpose

26
Q

where are allergies to fragrances most common on body?

what test is recommended whne using a new produtc?

A

Allergic reactions to fragrances most common on face, neck, skin around the eyes
Some fragrances are used as flavoring agents and rarely cause allergic reactions when ingested
cinnamon flavorings
Performing a “use test” recommended when using a new product

27
Q

function of preservatives in cosmetic, pharmaceuticals and industrial applications?

A

prevent bacterial and fungal overgrowth

28
Q

what are the most commonly used preservatives? (list a few)

A

Commonly used preservatives
formaldehyde
formaldehyde-releasing chemicals
methylchloroisothiazolinone/methylisothiazolinone
methyldibromoglutaronitrile phenoxyethanol
parabens

29
Q

KNOW: chemicals that release formaldehyde upon contact with skin?

A

Chemicals that release formaldehyde upon contact with the skin
Quaternium-15
DMDM hydantoin
Imidazolidinyl urea
Diazolidinyl urea
2-bromo-2-nitropropane-1,3-diol
Can be allergic to these individually or cross-react if allergic to formaldehyde

30
Q

where can preservative alleriges occur? is testing needed? what is tx?

A
  • *Reactions can occur at site of contact or be relatively diffuse**
  • *Testing is usually needed t**o detect and confirm allergy
  • *Avoidance is necessary once sensitized**
31
Q

types of reactions to latex rubber products?

A

**Immediate-type reactions to latex proteins: **
hives, itching, wheezing or anaphylaxis

Delayed-type reactions to chemical additives in rubber products
eczematous reactions

32
Q

what can synthetic rubbber products(such as nitirle) contain?

A

Synthetic rubber products (such as nitrile) can contain allergenic accelerators and other chemicals

33
Q

latex allergy:

  1. what type of allergy
  2. how do they occur and what type of rxns?
  3. have latex allergies improved?
A

1. Immediate-type hypersensitivity reactions to latex

  1. Reactions originally to powdered latex gloves
    Latex proteins adhere to powder and are aerosolized
    Reactions ranged from itching to death

3.Incidence has improved through elimination of powder, production of “better” gloves

34
Q

KNOW: what are three common rubber allergens?

A

Common rubber allergens include
thiurams
thiazoles
carbamates

35
Q

t/f. Use of chlorine bleach makes carbamates in elastic more allergenic

A

true

36
Q

two topical antibiotics that elicit allergic rxns/

A

neomycin
bacitracin

37
Q

topical antibiotic allergic rxns can be confused for __________

the use of topcial antibiotics on open skin may increase________

A

Reactions may be confused for infection
Use of topical antibiotics on open skin (dermatitis) may increase chance of developing allergy
Two antibiotics may cross react

38
Q

whar are the 4 most common plant allergens? (PACT)

A

Primrose

Alstroemeria

Chrysantemum

Tulip

39
Q

testing for ACD.

Experienced dermatologists predict relevant allergens only _____of time
_________ does not give info as to likely cause
_______ is gold standard

A

Experienced dermatologists predict relevant allergens only 50% of time
Skin biopsy does not give info as to likely cause
Patch testing is gold standard

40
Q

which allergy test used for immediate-type hypesensitivity?

which allergic test used for delayed-type hypersensitivity?

A

Prick (or scratch) testing tests for immediate-type hypersensitivity
detects allergies to foods, trees, grasses, molds, pets

Patch testing tests for delayed-type hypersensitivity reactions
Chemicals, metals, preservatives, fragrances, etc.

41
Q

how do you tx allergic contact dermatitis?

A

Symptomatic relief with cool compresses, oatmeal bathes, calamine lotion
Avoid Caladryl or any product with topical Benadryl (diphenydramine) which is potent sensitizer
Oral antihistamines generally OK
Topical corticosteroids
If oral corticosteroids needed, treat for at least 2-3 weeks in most cases

42
Q

tx of ACD: once dx is made ________ is only tx.

do allergy shots exist?

A

Once diagnosed, avoidance is the only “treatment”
There are no consistently effective desensitization methods for delayed-type hypersensitivity reactions
No “allergy shots”

Dermatology (18 decks)

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