contact derm Flashcards
which is the most common irritant or allergic?
irritant (80%) vs. allergic (20%)
**irritant is also the most common cause of occupational skin disease
what is the most common cause of ACD?
nickel (worldwide), poison ivy (USA)
who is at increased risk of contact derm
atopic derm, infants and elderly people. the latter 2 because of their decreased epidermal barrier
what is the pathogenesis of the ACD or ICD
ACD - delayed type IV hypersensitivity
ICD - cytotoxic, direct damage of keratinocytes
**ACD - patients only need exposure once every 3 weeks to keep allergic reaction going
cold temperature and low humidity
increased permeability to irritants
occlusion/maceration/increased humidity
increased permeability to water-soluble irritants
what is a co-reaction vs. cross-reaction?
co-reaction –> 2 molecules are necessary for allergic reaction, e.g. neomycin and bacitracin (NEOSPORIN), cobalt and nickel (seen in wheat, rye, oats, dried fruits, etc)
cross-reaction –> allergen to one item leads to allergen to similar item, e.g. poison ivy and mango, neomycin and gentamicin
what are the clinical symptoms of ICD vs. ACD? what are the histologic differences?
ICD - burning sensation, hands are the most common site of involvement, followed by the face, path: necrotic keratinocytes, mild spongiosis, and mild perivascular inflammation
ACD - itching sensation, path: spongiotic dermatitis with dermal infiltrate
Name that allergen (ACD edition):
- nail products
- Earlobe
- fabric finishers
- cosmetics
- perianal
- shoe dermatitis
- ulcers
- oral stomatitis
- tosylamide*, acrylates, formaldehyde, resin, glutaraldehyde, benzalkonium chloride
- nickel*
- formaldehyde* and formaldehyde releasers
- fragrances*, preservatives
- MCI/MI*, lidocaine
- adhesives (colophony), rubber (Mercaptobenzothiazole), leather (chromates), and dyes
- bacitracin, neomycin, lanolin
- dental fillings (mercury, gold, AMALGAM), epoxy resins, flavoring (mint/cinnamon)
Patch testing protocols
True test - 36 allergens (e.g. pink/red +, red, papules, and raised ++, red/raised/vesicles/papules +++)
First reading in 48 hours
Second reading in 72-96 hours***
Reactions that fade between 1-2 readings = irritant
Reactions that develop or continue between 1-2 readings = allergic
Delayed positive patch test (>1 week) - gold**, neomycin, dodecyl gallate, palladium, PPD, and corticosteroids. Positive patch test response to GOLD may last longer than 1 week.
Patch testing protocols
True test - 36 allergens (e.g. pink/red +, red, papules, and raised ++, red/raised/vesicles/papules +++)
First reading in 48 hours
Second reading in 72-96 hours***
Reactions that fade between 1-2 readings = irritant
Reactions that develop or continue between 1-2 readings = allergic
Delayed positive patch test (>1 week) - gold**, neomycin, dodecyl gallate, palladium, PPD, and corticosteroids.
Positive patch test response to GOLD may last longer than 1 week.
what are the cross-reaction
- mango, cashew, poison ivy/oak
- melon, watermelon, banana, avocado
- latex, kiwi, banana, avocado, chestnuts
RANDOM: UVA, UVB and UVC
UVA 320-400 nm
UVB 290-320 nm
UVC ? - 290 nm
only UVA and some UVB are able to reach the earth’s surface
ICD
- fiberglass dermatitis
- bodily fluids
- alkali’s
- acids (strongest: sulfuric and hydrofluoric acid)
- plants, may cause ACD, phytophoto, mechanical or chemical ICD
- Tx talcum powder
- Tx topical barrier protection
- Tx weak acid (lemon juice or vinegar)
- Tx for HF acid, neutralize with calcium gluconate gel and ER care. For phenol, neutralize with 65% ethyl or isopropyl alcohol
- Tx varies
Chemical ICD
- pineapple
- daffodil, hyacinth, tulip
- dumb cane
- red peppers
- croton plant, spurges, poinsettias, LATEX
- buttercups, marigolds
- garlic
- black mustard, radish
- bromelin**, ananas cosmos’s
- calcium oxalate**, amaryllidacea/lilacae
- calcium oxalate**, aracae
- solanaceae
- phorbol esters
- ranunculin**, ranunculacae
- thiocyanates, alliacea**
- thiocyanates, brassicaceae
