24 - Allergic Contact Dermatitis Flashcards
ACD accounts for _____% of new incident cases of contact dermatitis
20
Most prevalent contact allergens (retrospective study between 1996 and 2007
Nickel
Thimerosal
Fragrance mix
Y/N: Adults are more likely to develop ACD than children
No - equally likely
Increase in _____ (2) allergies with increasing age
Fragrance
Preservative
_____ sensitivity much higher among women
Nickel
Significant risk factor for the development of nickel allergy
Pierced ears
Sensitizing substance in poison ivy, poison oak, or poison sumac
Uroshiol
Key symptom for ACD
Pruritus
Type of ACD that occurs at the periphery of allergen application; linked primarily to exotic woods and topical medicaments
Erythema multiforme-like ACD
Type of ACD mainly described in Asian-ethnicity populations
Pigmented ACD
Type of ACD mainly observed on the lower legs and/or feet; associated with rubber and textile dyes
Purpuric ACD
Type of ACD based only on histopathologic criteria
Lymphomatoid ACD
Lymphomatoid ACD: presence of significant dermal infiltrate displaying features of
Pseudolymphoma
ACD hypersensitivity reaction
Cell-mediated (type IV) delayed hypersensitivity
Phases in the development of ACD
- Sensitization
2. Elicitation
Pigmented ACD also known as
Riehl melanosis
Unprocessed allergens which are typically small, lipophilic molecules with a low molecular weight (<500 daltons)
Haptens
Complete antigen is made up of
Hapten-protein complex
Hapten penetrates the skin and binds with
Epidermal carrier proteins
Sensitization phase generally lasts
10-15 days
Primary cells responsible for contact sensitization
CD1a+/CD141+ dermal dendritic cells
Most important population of cells in allergic sensitization
Th1/Tc1 subset
ACD phase that corresponds to clinical disease
Elicitation phase
Antigen-specific effector T cells containing their target antigen interact with antigen-presenting cells and cluster around postcapillary venukes
Inducible skin-associated lymphoid tissue
Diagnostic algorithm for ACD (2)
- Topographic approach
2. Allergen-specific approach
Single most important clue to the diagnosis of ACD
Dermatitis distribution
Topographic approach does not hold in (2)
Ectopic ACD
Airborne ACD
One of the most potent sensitizers known and widely used as an ingredient in hair dyes
Para-phenylenediamine
Chemical substance used in permanent wave solutions
Glyceryl monothioglycolate
Most women allergen accounting for isolated eye dermatitis (2007 NACDG analysis)
Gold
_____ of patients with isolated cheilitis - without other areas of dermatitis - are typically found to have an allergen as a contributing factor
1/3
Most common cause of contact allergy in patch-tested patients with cheilitis
Fragrance mix
Balsam of Peru
Repeated application of fragrances to the anterior neck may result in the appearance of a dermatitic plaque on the neck which has been coined the
Atomizer sign
Y/N: ACD of the axillae does not spare the axillary vault
No - relative sparing of axillary vault
80% of occupational skin disease
Hand dermatitis
Scattered generalized distribution is defined as (2)
Involvement of more than 3 body sites or
Involvement of 3 body sites if the sites are the trunk, arms, and legs
Higher incidence of scattered generalized distribution in (2)
Males
History of atopic dermatitis
Systemic contact dermatitis in which erythema of the buttocks and upper thighs are seen
Baboon syndrome
Dietary _____ (2) are associated with dyshidrosiform hand eczema
Nickel
Balsam of Peru
Potential cross-reactors with balsam of Peru
Tomatoes, citrus peel/zest, chocolate, ice cream, wine, beer, dark-colored sodas, spices such as cinnamon, cloves, curry and vanilla
ACD syndrome stage 1
Localized ACD
ACD syndrome stage 2
Regional dissemination of ACD
ACD syndrome stage 3A
Generalized or distant involvement of ACD
ACD syndrome stage 3B
Systemic exposure resulting in systemic contact dermatitis
Most common cause of ACD
Metals
Most frequently patch test-positive allergen worldwide
Nickel
Spot test for nickel
Dimethylgloxime
Added to other metals to increase the overall strength of an alloy; used in ceramics, paints, and tattoos to impart a blue color
Cobalt
Irritant effect from a deposition of cobalt within eccrine glands
Pseudopurpuric appearance
Sport test for cobalt
2-nitroso-1-naphthol-4-sulfonic acid
Has long been considered the classic marker for allergy to leather goods and wet cement
Chromium (potassium dichromate)
Aside from chromium, also a relevant marker for allergy to both leather and cement
Cobalt
Controversial allergen as it can often give a positive patch test but fail to meet standards for relevance; frequently manifests extremely delayed hypersensitivity
Gold
Colorless gas with preservative and disinfectant properties; found in glues, biocides, and photographic development agents
Formaldehyde
Among the preservatives, the most common cosmetic allergen is
Quaternium-15
Liked to two forms of ACD:
1) involves glues
2) involve wrinkle-free our permanent-press fabrics and clothing
Formaldehyde-containing resins
Two major non-formaldehyde releasing preservatives
Methyldibromoglutaronitrile/phenoxyethanol (MDBGN/PE)
Methylchloroisothiazolinone/methylisothiazolinone (MCI/MI)
Most allergic reactions to nonreleasers of formaldehyde originate from
Personal care products such as creams, lotions, wet wipes, liquid soaps, and medicated tissue and toilet paper
Up to _____% of the general population are allergic to fragrances
4
Main substances used by most patch test groups for screening for fragrance allergy
M. pereirae
Fragrance mix I
Fragrance mix II
2 antibiotics most commonly implicated in ACD
Neomycin
Bacitracin
Persists in its ability to cause ACD: died or permed hair
Permed hair
Adulterant added to natural henna; darkened the henna tattoo
Para-phenylinediamine
Individuals allergic to either the rubber accelerator/vulcanizer chemicals (or to latex itself) can safely use _____ gloves
Vicryl
Carbamates, mercaptobenzothiazole and thiuram are classified as
Rubber accelerator/vulcanizer chemicals
Safest steroid from an allergic standpoint
Desoximethasone ointment
Least-allergenic steroids belong to class
C
Thin-layer rapid-use epicutaneous (TRUE) test consists of
3 panels with a total of
35 allergens plus
1 blank control
Substance is applied to the cubital fossa twice a day for 1 to 3 weeks to simulate real life use
Repeat open application test or use test
Useful if testing liquid products with irritant potential; substance or dilutions of test substance applied to skin surface covering 1 cm2, allowed to evaporate and dry, then covered with hypoallergenic tape
Semiopen patch test
Represents a weak nonvesicular reaction but with palpable erythema
+
Represents a strong (edemstous or vesicular) reaction
++
Represents an extreme (bullous or ulcerative) reaction
+++
Represenrs macular (nonpalpable) erythema
Doubtful
Irritant patch test reactions can be classified into: (3)
Erythematous reactions
Purpuric reactions
Pustular reactions
Purpuric reactions with petechial hemorrhage seen in approximately 5% of patients tested to
Cobalt chloride (punctate purpura of cobalt)
Pustular reactions are most commonly encountered with
Metalic salts
Early appearing: allergic vs irritant pattern
Irritant
Usually spreads, slowly disappearing: allergic vs irritant pattern
Allergic
Mercuric preservative that commonly causes positive patch test reactions but very seldom accounts for the patient’s dermatitis; present in vaccines
Thimerosal
Clinical relevance assessment classification
Current: possible or probable
Past
Doubtful
Most common side effects of patch testing
Itching at the site of a positive test reaction
Irritation or pruritus from tape application
Persistent patch test reactions are defined as patch test reactions that persist for
More than 1 month
Persistent patch test reactions occur most commonly from
Gold salts
Anaphylasix most often reported with
Ammonium persulfate
