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Eczematous dermatoses > Contact dermatitis > Flashcards

Contact dermatitis Flashcards

1
Q

What percent of contact derm is irritant vs allergic?

A
  • 80% irritant!! - 20% allergic
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2
Q

Most common cause of allergic contact derm (ACD) world-wide: - in the US:

A
  • worldwide is nickel - USA is poison ivy
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3
Q

Which populations have increased risk of contact dermatitis?

A
  • infants, elderly, and Atopic derm patients due to increased penetration of contactants
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4
Q

Pathogenesis of Irritant contact derm (ICD)

A
  • direct damage of keratinocytes by irritant - does NOT require sensitization and pretty much everyone who comes into contact with these substances will have this reaction
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5
Q

Acids or bases are stronger irritants to the skin?

A
  • Bases
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6
Q

Pathogenesis of allergic contact dermatitis:

A
  • immune-mediated, delayed- type IV hypersensitivity reaction - requires initial sensitization to allergen - preexposure to allergen–> T cell mediated release of cytokines/chemotactic factors–>eczema within 48 hours
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7
Q

How often do you need an exposure to allergen to keep ACD reaction going?

A
  • once every 3 weeks
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8
Q

What is a cross-sensitization in ACD?

A
  • sensitization to one compound results in sensitization to a similar compound, even if you haven’t been exposed to the other compound
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9
Q

Symptoms of irritant CD

A
  • burning may be more common than itch
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10
Q

most common sites involved in ICD?

A
  • # 1 is hands - #2 is face
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11
Q

Pustular/acneiform ICD results from which irritants?

A
  • metals!! or metal-like liquids - tars, greases
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12
Q

Airborne irritant CD resembles a photo allergic reaction, but involves_______ (parts of body)

A
  • upper eyelids, philtrum, submental region
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13
Q

Pathogenesis of phytophotodermatitis?

A
  • fucocoumarins + UVA light–>erythema +/- blistering within 24-72 hours—> followed by hyperpigmentation 1-2 weeks later
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14
Q

Berloque dermatitis presents clinically as_____ and is caused by _____

A

pigmentation of neck/trunk/arms from cologne application containing bergamot oil

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15
Q

Clinical presentation of allergic contact dermatitis:

A
  • erythema/edema/papules/oozing/vesicles with sharp demarcation between uninvolved skin.
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16
Q

Subacte allergic contact dermatitis will have _____ present clinically which is not typically seen in acute.

A
  • scale/crust!

- histopath will show acanthosis

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17
Q

Chronic ACD will present with:

A
  • marked lichenification no vesicles, less well-defined than acute, and may spread beyond site of exposure
18
Q

Distribution of contact dermatitis will depend on the exposure:

  • Linear ACD commonly due to _____
A
  • rhus (poison ivy/poison oak/poison sumac)
19
Q

Contact derm on fingertips in florists most commonly due to ____

A
  • allergic contact to Tulips
20
Q

ACD resulting perioral/baboon syndrome is due to which allergens?

A
  • flavorings, foods, cosmetics, shellac, meds, and sunscreens
21
Q

Periocular/eyelid ACD is commonly due to which allergens?

A

Nail products (tosylamide > acrylates, formaldehyde, resin, glutaraldehyde, and benzalkonium chloride)

Cosmetics (false eyelashes, adhesives, mascara, rubber sponges for make-up, and eye-shadow)

Other allergens: gold (rings), other metals, volatile gases, fragrances/balsam of Peru, neomycin, surfactants, and preservatives

22
Q

ACD on earlob most commonly caused by:

A
  • Nickel
23
Q

ACD on wrist is commonly caused by:

A
  • Chromates in leather watches (check out my chrome watch)
24
Q

Clothing dermatitis: spares the ____ and is accentuated _____

A
  • skin folds (axillary vault)
  • accentuated where clothing fits tightly (Waist)
25
Q

Most common clothing allergens:

A

Fabric finishers (i.e., anti-wrinkle and stain repellant): formaldehyde and formaldehyde releasers

Dyes (disperse blue dyes 106 and 124)

Rubber (bleached underwear → bleaching causes release of carbamates)

26
Q

Number 1 and 2 most common cosmetic ACD are:

A
  • # 1= Fragrance!
  • # 2= preservatives
27
Q

Shoe dermatitis generally spares the ______

A
  • toe webs and plantar surface
28
Q

Causes of shoe ACD:

A
  • Colophony in adhesives
  • mercaptobenzothiazole in rubber
  • Chromates
29
Q

Which topical antimicrobials are the biggest culprits for ACD:

A
  • Bacitracin and Neomycin (polymyxin B much less common)
  • remember BNP for the triple antibiotic ointments, P is the last letter and least likely to cause ACD.
30
Q

Airborne ACD usually caused by _____ with ____ being the number 1 chemical involved

A
  • Plants cause airborne ACD most frequently
  • Compositae is the compound most commonly involved
31
Q

Most reactions to adhesives are ____ (ACD or ICD)

A
  • ICD
32
Q

Histopath of ICD:

A
  • mild spongiosis, scattered necrotic keratinocytes (from direct toxic injury 2/2 irritant), and mild perivascular inflammation
33
Q

Histology of ACD:

A

spongiotic dermatitis (may be acute/subacute/chronic, depending on stage), more prominent dermal inflammation

vs ICD: ↑spongiosis, ↑dermal inflammation w/ eosinophils, and lacks necrotic keratinocytes

- chronic will have more acanthosis and less spongiosis

34
Q

What test can you do to confirm Allergic contact derm?

A
  • patch testing
35
Q

Describe timeline of patch testing in clinical practice.

A
  • day 1 place patches on skin free of dermatitis (monday)
  • after 48 hours, remove patches and record reactions (wednesday)
  • after another 1-3 days, make a second recording (friday)
36
Q

Reactions on patch test that fade between the first and second reading are caused by____

A
  • irritants
37
Q

Reactions that continue or develop between first and second readings on patch test are due to ______

A
  • allergen (as opposed to irritant, which would improve between the two readings)
38
Q

Which substances can cause a delayed positive patch test?

A
  • corticosteroids and gold! (as well as neomycin dodecyl gallate, palladium, p-phenylenediamine)
39
Q

What materials contain chromates?

A
  • dyes (green felt fabric on pool table), yellow-green pigment (tattoos/cosmetics), leather (shoe dermatitis), cement

- picture Dr. Grumpy pants in a pool bar, wearing a leather jacket, with a green-yellow tattoo walking barefoot on cement floor.

40
Q

Cobalt is present in what products?

A

metal products, cosmetics, dyes (blue-green dyes, paint, tattoos), glass/pottery, cement, vitamin B12 injections (can lead to intractable hand dermatitis), and artificial joints

41
Q

Mercury allergy is commonly seen in what situation?

A
  • in mouth with dental amalgams causing oral lichenoid reaction.
42
Q

Most common cause of persistently positive patch test reaction is caused by _____

A
  • gold

Eczematous dermatoses (8 decks)

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