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Allergy and Immunology > First Aid, Chapter 7 Hypersensitivity Disorders, Contact Hypersensitivity > Flashcards

First Aid, Chapter 7 Hypersensitivity Disorders, Contact Hypersensitivity Flashcards

1
Q

What is the pathogenesis of contact hypersensitivity?

A

Contact hypersensitivity (CHS) is a type IV hypersensitivity that is mediated by CD4 and CD8 lymphocytes stimulated by epidermal antigenpresenting cells (Langerhans cells).

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2
Q

In contact hypersensitivity, how quickly does dermatitis develop upon reexposure if already sensitized?

A

12-18 hours.

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3
Q

What are common histologic features of contact dermatitis?

A

Lymphocytic infiltration and spongiosis.

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4
Q

What are the scores and final reads that correlate with them for patch testing?

A 
- negative reaction
? or +/- doubtful reaction
\+ weak reaction
\++ strong reaction
\+++ extreme reaction
IR irritant reaction
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5
Q

What is the appearance of a doubtful reaction on patch testing?

A

Limited to faint macular erythema; use caution when interpreting, especially with less common allergens

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6
Q

What is the appearance of a weak reaction on patch testing?

A

Erythema and edema that is palpable with slight infiltration that occupies >50% of patch test site

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7
Q

What is the appearance of a strong reaction on patch testing?

A

Microvesicles and erythema that occupy at least 50% of patch test site.

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8
Q

What is the appearance of an extreme reaction on patch testing?

A

Confluent vesicles or bullae, ulcerative.

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9
Q

What is the appearance of an irritant reaction on patch testing?

A
  • Mild: glazed appearance
  • Moderate: follicular (pustular in atopics)
  • Extreme: can be ulcerative
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10
Q

What is the mechanism of allergic contact dermatitis?

A

Characterized by an antigen-specific T–lymphocyte-mediated hypersensitivity reaction.

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11
Q

What is the percentage of different distributions of an allergic contact dermatitis?

A

Location: Hands 27%, generalized 18%, face 16%, eyelids 5%, trunk 5%, and feet 3%.

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12
Q

What is the crescendo phenomenon in patch reading? What type of contact dermatitis does it pertain to?

A

“Crescendo” phenomenon, where positive reactions to patch test become more marked between first and second readings in allergic contact dermatitis.

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13
Q

What is the typical symptom of allergic contact dermatitis?

A

Characterized by severe pruritus, reactions usually take 12–48 hours to develop.

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14
Q

What is the most prevalent form of contact dermatitis? What is the percentage that are this type?

A

Irritant contact dermatitis, 80%.

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15
Q

What is the mechanism of irritant contact dermatitis? Is prior sensitization required? Why or why not?

A

Irritants cause inflammation of the skin induced by chemicals, oxidants, or alkali, surfactants, and solvents that directly damage the skin. No previous sensitization is required; it reflects nonspecific toxicity of the antigen

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16
Q

What are typical symptoms of irritant contact dermatitis? What is typical in patch reading?

A

Characterized by stinging and less pruritic than ACD, reaction almost immediate. “Decrescendo” is typical as reactions tend to decrease in severity between readings.

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17
Q

What is photocontact dermatitis?

A

A photoallergic or phototoxic chemical requires light-induced excitation in the ultraviolet spectrum to cause dermatitis.

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18
Q

What are some photoallergic agents (require prior sensitization)?

A

Para-Aminobenzoic acid (PABA), chlorhexidine, thiourea, NSAIDs, thiazide diuretics, dapsone, and sulfonylureas.

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19
Q

What are some phototoxic agents (do not require prior sensitization)?

A

Psoralens, furocoumarins, tar, lime, celery, parsnip, tetracyclines, amiodarone, diuretics, quinine, and NSAIDs.

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20
Q

What are IgE-dependent agents that cause contact urticaria?

A

Dairy products, seafood, various fruits, grains, topical antibiotics, metals, preservatives, and plants

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21
Q

What are IgE-independent agents that cause contact urticaria?

A

Fragrances, arthropods, jellyfish, and coral.

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22
Q

What is the mechanism of contact urticaria?

A

Can be either immunologic or nonimmunologic

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23
Q

What are the ten most common contact allergens in the US?

A
  • Nickel sulfate
  • Neomycin
  • Myroxylon pereirae (balsam of Peru)
  • Fragrance mix
  • Thimerosal
  • Sodium gold thiosulfate
  • Quaternium-15
  • Formaldehyde
  • Bacitracin
  • Cobalt chloride
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24
Q

What are common metals that cause contact dermatitis?

A
  • Potassium dichromate: Stainless steel, chrome plating other metals, and tanned leather
  • Chromates: Textile, leather tanners, and construction workers using wet cement
  • Cobalt dichloride: (Uncommon) dental implants, artificial joints, and engines or rockets
  • Nickel: Nonoccupational exposure, jewelry; dimethylglyoxime test of nickel-containing material (pink = positive).
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25
Q

What is the most common form of allergic contact dermatitis?

A

Toxicodendron dermatitis (aka poison ivy, poison oak, and poison sumac) is the most common form of ACD.

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26
Q

What is the cause of allergic contact dermatitis to Toxicodendron (poison ivy/oak/sumac)?

A

It is caused by urushiol, an oleoresin that is found in the sap and oozes readily from any crushed part of the plant.

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27
Q

How long does it take for sensitivity to toxicodendron to occur? What percentage of the population will have a reaction to it? What percentage of the population will have a severe reaction to it? What are the symptoms of a severe reaction?

A

Sensitivity to Toxicodendron usually develops after several encounters with the plants, which, in some cases, may occur after many years of exposure. Studies suggest that ~85% of the population will develop a clinical reaction when exposed; however, 10–15% of the population is believed to be highly susceptible to poison ivy and poison oak. These people develop systemic symptoms, which include rashes with swelling of the face, arms, and genitalia.

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28
Q

What fruit does toxicodendron cross-react with?

A

mango peel

29
Q

What is the group name of poison ivy plants?

A

Anacardiaceae

30
Q

Where are the sensitizing agents in plants mostly present?

A

The sensitizing substances in most plants are present mainly in the oleoresin fraction; in some plants, the allergens are water-soluble glucosides. Most plants must be crushed to release the antigenic chemicals.

31
Q

What is the most common cause of hand eczema in flower workers? What is the distribution of the rash?

A

In the US, Alstroemeria, also called Peruvian lily, is the most frequent cause of hand eczema in flower workers. This classic dermatitis is an intensely pruritic eruption that affects the first three fingers and exposed areas of dorsal hands, forearms, the V-region of the neck, and the face.

32
Q

What is the family of giant and dwarf ragweed? What is the antigen? What condition does this antigen cause?

A

Family Ambrosia
Antigen - Sesquiterpene lactones
Allergic contact dermatitis

33
Q

What are the antigens that cause ACD in florists and bulb growers? How should they be tested?

A

Sesquiterpene lactones and tuliposides are large, diverse groups of chemicals found in several plant families that cause ACD in florists and bulb growers. Test the actual chrysanthemum (petal, leaf, and stem) as no single sesquiterpene is sufficient to screen for sensitivity to chrysanthemums. b Primin is the most common ACD in Europe.

34
Q

What is the family of Chrysanthemums and daisies? What is the antigen? What condition does this antigen cause?

A

Family Compositae
Antigen Sesquiterpene
Allergic contact dermatitis

35
Q

What is the family of Tulips, hyacinth, asparagus, and garlic? What is the antigen? What condition does this antigen cause?

A

Family Liliaceae
Antigen Tuliposide
Allergic contact dermatitis

36
Q

What is the family of Daffodil and narcissus? What condition do these plants cause?

A

Family Amaryllidaceae

Allergic contact dermatitis

37
Q

What is the family of Primula? What is the antigen? What condition does this antigen cause?

A

Family Primrose
Antigen Primin
Allergic contact dermatitis

38
Q

What is the family of carrots, celery, and parsnips? What condition do these plants cause?

A

Family Umbelliferae

Allergic contact dermatitis

39
Q

What is the family of nettles? What condition does this plant cause?

A

Family Urticaceae

Allergic contact dermatitis

40
Q

What is the family of oranges, lemons, and grapefruits? What condition do these plants cause?

A

Family Rutaceae

41
Q

What are typical contact allergens in cosmetics?

A

Fragrances, preservatives, formulation excipients, glues, and sunblocks.

42
Q

What is the most common cause of CD in personal products in the US?

A

Fragrances

43
Q

What is a common fragrance that is used in personal products? What else is it used at? What does it cross-react with?

A

Fragrances are among the most common causes of CD in the US. Balsam of Peru has a spicy scent and is used in the manufacture of perfumes, but it is also used as a flavoring agent. Balsam of Peru has wide cross-reactivity, but most prominent are cinnamon and vanillin.

44
Q

What are the two categories of preservatives?

A

Formaldehyde donors (i.e., products that emit formaldehyde) and nonformaldehyde donors

45
Q

List the formaldehyde releaser preservatives.

A

Diazolinidinyl urea, Imidazolindinyl urea, Quaternium-15,
DMDM ( dimethylol dimethyl) hydantoin,
Bromonitropropane

46
Q

List the nonformaldehyde donor preservatives.

A 
Parabens
Methylisothiazolinone
Phenoxyethanol
PCMX (parachlorometaxylenol)   and/or PCMC (parachlorometacresol)
Benzalkonium chloride
Thimerosal
47
Q

What is the most common preservative in cosmetics? Does it commonly cause ACD?

A

parabens, not a common cause of ACD.

48
Q

What is the most frequent preservative cause of ACD in the US?

A

Quaternium-15

49
Q

What are formulation excipients? List them.

A

—Defined as inert substances that serve to solubilize, emulsify, sequester, thicken foam, lubricate, or color the active component in a product.

Antioxidants (sulfites) Propylene glycol Benzylalkonium chloride EDTA (ethylenediamine tetraacetic acid) Ethylenediamine Cetrimide Butylene glycol Vegetable gums Lanolin Polyethylene glycol Chlorocresol Chloramine-T Triethanolamine Thimerosal Butyl alcohol

50
Q

What types of products are the first and second most common causes of cosmetic ACD?

A

1) skin products

2) hair products

51
Q

What are common chemicals in hair products that cause CD? What types of products are they found in?

A
  • Cocamidopropyl betaine: Shampoos, eye and/or facial cleaners, and bath products
  • Paraphenylenediamine: Most common cause of contact hypersensitivity (CHS) in hair dressers
  • Glycerol thioglycolate: Permanent wave solution
52
Q

What are the common chemicals in nail polish that cause contact dermatitis? Where does the contact dermatitis present? How should it be tested? What other chemical should you suspect in nail polish?

A

Acrylics—In nails can present locally at the distal digit or ectopically on the eyelids and face. Patch testing to a variety of acrylates and nail polish resins may be necessary to delineate the causative agent. Ethylacrylate has been demonstrated to detect a higher number of acrylate-allergic patients. Formaldehyde-based nail resins should also be suspected and tested when ectopic facial dermatitis is present.

53
Q

What are common causes of photoallergic ACD? What is a good alernative that is rarely sensitizing? How is photoallergic ACD diagnosed? Describe the testing.

A

Sunblocks or Sunscreens—Common causes of photoallergic ACD. These are frequently present in cosmetics such as moisturizers, “facial” creams, lip and hair preparations, and foundations. “Chemical-free” sunblocks use physical-blocking agents (micronized titanium dioxide and zinc oxide) and are rare sensitizers. Photoallergic CD is diagnosed with photopatch testing. This combines patch testing with ultraviolet type A (UVA) exposure (320–400 nm of ultraviolet light). Pure photoallergens only cause a skin hypersensitivity reaction with both UVA light and chemical exposure.

54
Q

What percent of ACD is caused by topical corticosteroids?

A

5%.

55
Q

What are risk factors for ACD to topical corticosteroids?

A

Risk factors include treatment of refractory eczema, leg ulcers, and stasis dermatitis.

56
Q

What is the typical presentation of ACD to topical corticosteroids?

A

The patient usually notes a failure to improve or experiences a flare-up of the underlying dermatitis being treated with the steroid.

57
Q

How should patch testing be done when a topical steroid is suspected?

A

Patch test readings should also be done 7 days after application because of the immunosuppressant nature of the test reagent itself (false negatives are common).

58
Q

What are the most common screening agents for patch testing for topical corticosteroids?

A

The most commonly used screening agents in patch testing for topical corticosteroid allergy are budesonide and tixocortol pivalate 1%.

59
Q

What are the 4 major chemical classes of sensitizing corticosteroids? Do patients react to all 4?

A

o Group A: Hydrocortisone type
o Group B: Triamcinolone type
o Group C: Betamethasone type
o Group D: Hydrocortisone-17-butyrate type
-Patients do not usually react to all four classes, so there are safe corticosteroids. It is important to distinguish among the four classes.

60
Q

What resins cause ACD?

A
  • Epoxy
  • Colophony
  • Ethylenediamine dihydrochloride
  • Paraphenylenediamine
  • Topical antibiotics
61
Q

What form is epoxy sensitizing?

A

Epoxy, when cured, is nonsensitizing; ACD occurs with uncured resin (90%) or to hardener.

62
Q

What is colphony made from? What products is it in? Can it be tested? What cross-reacts with it?

A

Colophony is made from pine trees and appears in cosmetics, topical medications, and industrial products. Different pine trees mean different forms of colophony (testing is difficult), and Balsam of Peru may cross-react.

63
Q

What topical antibiotics can cause ACD? Can they cause anaphylaxis? What do they cross-react with?

A

Topical antibiotics such as bacitracin (or Neomycin) are common and iatrogenic with risk of anaphylaxis that can be delayed. Neomycin is the most commonly used antibiotic and is an aminoglycoside that cross-reacts with gentamicin, kanamycin, streptomycin, and tobramycin. There is crossreactivity with bacitracin. If patient is sensitive, the physician should avoid prescribing all of these antibiotics.

64
Q

Where is Ethylenediamine dihydrochloride found? Does it cross-react with EDTA? What medications should those sensitive to ethylenediamine dihydrochloride avoid?

A

Ethylenediamine dihydrochloride appears in topical creams, aminophylline, and generic nystatin. EDTA does not appear to cross-react with ethylenediamine. If sensitive, avoid nystatin, aminophylline, and piperazine-based antihistamines (e.g., meclizine and cyclizine).

65
Q

Where is paraphenylenediamine found?

A

Paraphenylenediamine is a derivative of benzene and common, epidemic with “henna” tattoos (also most common cause of CHS in hair dressers because it is in hair dye). Patients are not allergic to the henna, but to the contaminating paraphenylenediamine.

66
Q

What are common causes of allergic contact cheilitis (ACC)? Is ACC common?

A

A common form of ACD, because the epithelium of the lips is similar to that of the skin. Common ACC contactants include:

  • Dental devices
  • Lipsticks
  • Lip balms
  • Nail polish
  • Cigarette paper
  • Various essential oils
67
Q

How are surgical implant dermtitises diagnosed?

A

The four criteria for diagnosis of a cutaneous implant-induced reaction are:

  • Dermatitis (localized or generalized), appearing after implant surgery
  • Persistent dermatitis that is resistant to appropriate therapies
  • A positive patch test result to a metallic component of the implant or to acrylic glues
  • Resolution of the dermatitis after removal of the implant
68
Q

What is systemic contact dermatitis? What is typically observed on exam? What routes of administration can it occur with?

A

Systemic contact dermatitis (SCD) is a generalized ACD rash from systemic administration of a drug, chemical, or food to which the patient previously experienced ACD. Patients allergic to topical antihistamines (e.g., Benadryl cream) may develop systemic CD after systemic administration of diphenhydramine. This has been termed the “baboon syndrome” because of the indurated erythema that may be observed in the groin area of afflicted patients. Reactions have also occurred after systemic and intra-articular use of corticosteroids to which a patient had been topically sensitized

Allergy and Immunology (68 decks)

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