24: Allergic Contact Dermatitis Flashcards
What is the primary cause of Allergic Contact Dermatitis (ACD)?
Allergic Contact Dermatitis is caused by skin contact with an environmental allergen leading to a cell-mediated (type IV) hypersensitivity reaction.
What are the three phases of Allergic Contact Dermatitis?
The three phases of Allergic Contact Dermatitis are:
1. Acute phase: characterized by pruritus, erythema, edema, and vesicles.
2. Subacute phase: involves vesicular rupture leading to oozing and scaly papules.
3. Chronic phase: presents as lichenified erythematous plaques with variable hyperkeratosis and pigmentary changes.
What is the significance of patch testing in the diagnosis of ACD?
Patch testing is the diagnostic test of choice to identify causal allergens and is indicated for patients with persistent or recurrent dermatitis in whom ACD is suspected.
How does age influence the prevalence of contact allergies?
Age influences the prevalence of contact allergies as follows:
- Adults 28-75 years: higher prevalence of allergy to fragrance.
- Adults 41-60 years: higher prevalence of allergy to preservatives.
What are the clinical features of Allergic Contact Dermatitis?
The clinical features of Allergic Contact Dermatitis include:
- Pruritic, eczematous dermatitis initially localized to the primary site of allergen exposure.
- Geometric, linear, or focal patterns of involvement suggestive of an exogenous etiology.
- Poison Ivy ACD presents as a linear or streaky array of erythematous papules and vesicles.
What is the role of Langerhans cells in the sensitization phase of ACD?
In the sensitization phase of ACD, Langerhans cells (a type of antigen presenting cell) take up the hapten-protein complex and express it on their surface, presenting it to naïve T cells in the lymph nodes, which is crucial for developing an immune response.
What is the median prevalence of contact allergy in the general population?
The median prevalence of contact allergy in the general population is 21.2%, with variations based on gender and specific allergens.
What are the two distinct phases in the development of Allergic Contact Dermatitis?
The two distinct phases in the development of Allergic Contact Dermatitis are:
1. Sensitization phase: lasts 10-15 days and is asymptomatic.
2. Elicitation phase: occurs upon subsequent exposure to the antigen, leading to an allergic reaction.
A patient presents with pruritic, eczematous dermatitis localized to the wrist. They frequently wear a nickel bracelet. What is the likely diagnosis and the diagnostic test of choice?
The likely diagnosis is Allergic Contact Dermatitis (ACD) caused by nickel. The diagnostic test of choice is patch testing.
What are the key phases of allergic contact dermatitis (ACD) and their characteristics?
- Sensitization Phase:
- Lasts 10-15 days, asymptomatic
- Initial exposure to allergen leads to immunologic memory formation.
- Elicitation Phase:
- Subsequent exposure to the same allergen triggers an inflammatory response, resulting in symptoms such as pruritus, erythema, and vesicles.
How does the prevalence of contact allergy differ by age and gender?
- Age:
- Adults 28-75 years: Higher prevalence of fragrance allergy.
- Adults 41-60 years: Higher prevalence of preservatives allergy.
- Gender:
- Median prevalence of contact allergy: 21.8% in women vs. 12% in men.
- Pierced ears are a significant risk factor for nickel allergy in women.
What clinical features are indicative of allergic contact dermatitis (ACD)?
- Classic Presentation:
- Pruritic, eczematous dermatitis localized to the site of allergen exposure.
- Patterns of Involvement:
- Geometric, linear, or focal patterns suggestive of exogenous etiology.
- Specific Types:
- Poison Ivy ACD: Linear or streaky erythematous papules and vesicles.
- Lichenoid ACD: Rare variant mimicking lichen planus.
- Pigmented ACD: Mainly described in Asian populations.
What is the role of hapten in the sensitization phase of allergic contact dermatitis?
- Hapten:
- Unprocessed allergens that are small, lipophilic molecules with low molecular weight (<500 daltons).
- They penetrate the skin and bind with epidermal carrier proteins to form a hapten-protein complex, which is essential for the immune response.
- Process:
- The hapten-protein complex is presented to T cells, leading to sensitization and subsequent allergic reactions upon re-exposure.
What are the steps involved in the sensitization phase of allergic contact dermatitis?
- Innate Immunity Activation: Release of cytokines (IL-1, IL-8, TNF-α, GMCSF).
- Antigen Presentation: Langerhans cells or dermal dendritic cells take up the hapten-protein complex and present it on HLA molecules.
- Migration to Lymph Nodes: APCs migrate to regional lymph nodes to present the HLA complex to naïve T cells.
- T Cell Priming: Naïve T cells differentiate into memory T cells, acquiring skin-specific homing antigens.
- Immigration into Circulation: Memory T cells circulate and act on target cells presenting the same antigen in the future.
What are the steps involved in the elicitation phase of allergic contact dermatitis (ACD)?
- Hapten exposure leads to low-grade nonspecific inflammation through cellular stress.
- Activation of toll-like receptors and nucleotide-binding oligomerization domain-like receptors results in neutrophil recruitment and effector T-cell recruitment.
- Interaction with APCs occurs in a cluster around postcapillary venules.
- Antigen-specific T cells release cytokines (INT-g and TNFa).
- An inflammatory response occurs, leading to monocytes migrating into the affected area, maturing into macrophages, and attracting T cells.
What are the misconceptions about allergic contact dermatitis (ACD)?
- ACD is not always bilateral, even when the antigen exposure is bilateral (e.g., shoe or glove allergy).
- Exposure to an allergen can be uniform (e.g., contact allergy to a cream), but eczematous manifestations are often patchy.
- ACD can affect the palms and soles.
What is the significance of the topographic approach in diagnosing allergic contact dermatitis (ACD)?
The topographic approach is crucial in diagnosing ACD as it is based on the distribution of dermatitis on the patient’s skin. This approach helps identify specific allergens related to the dermatitis patterns observed.
What are common allergens associated with eyelid dermatitis in allergic contact dermatitis?
Common allergens associated with eyelid dermatitis include:
- Tosylamide formaldehyde resin found in nail lacquer.
- Phenylmercuric acetate and antibiotics, which are preservatives frequently found in ophthalmic preparations.
What are the typical presentations of allergic contact dermatitis on the face and scalp?
Face: The prototypical presentation is preauricular facial dermatitis, often seen in nickel-allergic patients.
Scalp: PPD is a potent sensitizer used in hair dyes, causing intense scalp pruritus with scaling, edema, and crusting.
A 35-year-old hairdresser develops dermatitis on their hands. What allergen is most likely responsible, and what is the recommended diagnostic approach?
The most likely allergen is para-phenylenediamine (PPD) from hair dyes. The recommended diagnostic approach is patch testing.
A patient presents with erythema and scaling on the eyelids. They frequently use nail polish. What is the likely cause, and why are the eyelids particularly sensitive?
The likely cause is ectopic contact dermatitis from tosylamide formaldehyde resin in nail polish. Eyelids are particularly sensitive due to their thin skin and the accumulation of offending chemicals in eyelid folds.
A patient develops dermatitis on the lips after using a new sunscreen. What ingredient is likely responsible, and what is the condition called?
The likely ingredient is benzophenone-3 (oxybenzone). The condition is called allergic contact cheilitis.
A patient presents with dermatitis on the eyelids after using a new ophthalmic preparation. What allergens should be suspected, and why are the eyelids particularly vulnerable?
Suspected allergens include phenylmercuric acetate and antibiotics. Eyelids are particularly vulnerable due to their thin skin and the accumulation of offending chemicals in eyelid folds.
A patient develops dermatitis on the scalp after using a permanent wave solution. What chemical is likely responsible, and what are the clinical features?
The likely chemical is GMT (glyceryl monothioglycolate). Clinical features include intense scalp pruritus with scaling, edema, and crusting.
What are the key steps involved in the elicitation phase of allergic contact dermatitis (ACD)?
- Hapten exposure leads to low-grade nonspecific inflammation through cellular stress.
- Activation of toll-like receptors and nucleotide-binding oligomerization domain-like receptors results in neutrophil recruitment and effector T-cell recruitment.
- Interaction with APCs occurs in a cluster around postcapillary venules.
- Antigen-specific T cells release cytokines (INT-g and TNFa).
- An inflammatory response occurs, with monocytes migrating into the affected area, maturing into macrophages, and attracting T cells.
How does the topographic approach aid in the diagnosis of allergic contact dermatitis (ACD)?
The topographic approach is crucial for diagnosing ACD as it focuses on:
- Dermatitis distribution: This is the single most important clue to the diagnosis of ACD.
- Allergen-specific approach: This is based on knowledge of trends in dermatitis related to specific allergens, helping to identify the source of the allergic reaction.
What is the clinical significance of heterotransfer in allergic contact dermatitis (ACD)?
Heterotransfer in ACD is clinically significant because:
- It describes how an allergen can be transferred to a patient by another person (e.g., spouse or parent).
- This can lead to unexpected allergic reactions in individuals who may not have direct exposure to the allergen themselves, complicating diagnosis and management.
What is the prototypical presentation of allergic contact dermatitis (ACD) in the axillae?
The prototypical presentation is an eczematous dermatitis affecting the axillary folds with relative sparing of the axillary vault.
What is Baboon syndrome and its characteristics?
Baboon syndrome is characterized by:
- Erythema of the buttocks and upper inner thighs
- Broadened to include cases of drug-induced erythema of the buttocks and upper inner thighs.
What are the stages of allergic contact dermatitis syndrome?
The stages are:
1. Stage 1: Localized allergic contact dermatitis
2. Stage 2: Regional dissemination of allergic contact dermatitis
3. Stage 3A: Generalized or distant involvement of allergic contact dermatitis
4. Stage 3B: Systemic exposure resulting in systemic contact dermatitis.
What is the significance of nickel in allergic contact dermatitis?
Nickel is the most frequently patch test-positive allergen worldwide, with sensitization rates of 18-30%. It is commonly found in:
- Earlobes
- Neckline
- Wrist
- Periumbilical area.
What are the common sources of systemic contact dermatitis (SCD)?
Common sources of SCD include:
- Subcutaneous exposure to allergens
- Intravenous or intramuscular exposure
- Inhalation of allergens
- Oral ingestion of allergens.
What are the diagnostic criteria for Symmetrical drug-related intertriginous and flexural exanthema (SDRIFE)?
The diagnostic criteria for SDRIFE include:
1. Exposure to a systemically administered drug either at the first or repeated dose.
2. Sharply demarcated erythema of the gluteal/perianal area and/or V-shaped erythema of the inguinal/perigenital area.
3. Involvement of at least one other intertriginous/flexural localization.
4. Symmetry of affected areas.
5. Absence of systemic signs or symptoms.
A patient with a history of pierced ears presents with dermatitis around the earlobes. What allergen should be suspected, and how can exposure be minimized?
Nickel should be suspected. Exposure can be minimized by regulating the amount of nickel released from objects to ≤0.5 μg nickel/cm²/week.
A patient presents with erythema and vesicles on the anterior neck after using a new perfume. What is the likely diagnosis, and what is the term for this presentation?
The likely diagnosis is Allergic Contact Dermatitis (ACD) caused by fragrance allergens. The term for this presentation is the ‘atomizer sign.’
A healthcare worker develops chronic hand dermatitis. What occupations are at increased risk for this condition?
Occupations at increased risk for chronic hand dermatitis include health care workers, food handlers, and hairdressers.
How can exposure to nickel be minimized?
Exposure can be minimized by regulating the amount of nickel released from objects to ≤0.5 μg nickel/cm²/week.
What is the likely diagnosis for a patient with erythema and vesicles on the anterior neck after using a new perfume?
The likely diagnosis is Allergic Contact Dermatitis (ACD) caused by fragrance allergens.
The term for this presentation is the ‘atomizer sign.’
What occupations are at increased risk for chronic hand dermatitis?
Occupations at increased risk include healthcare workers, food handlers, and hairdressers.
What is the next step in management for chronic hand dermatitis?
The next step in management is patch testing to identify allergens.
What allergens should be suspected in a patient with dermatitis on the torso after wearing a new shirt?
Suspected allergens include disperse dyes and formaldehyde textile resins, which are associated with textiles.
What is the likely chemical responsible for dermatitis on the perianal area after using a proctologic preparation?
The likely chemical is benzocaine.
The condition is called contact dermatitis of the perianal area.
What allergens should be suspected in a patient with dermatitis on the hands and frequent use of rubber gloves?
Suspected allergens include rubber-related chemicals such as mercaptobenzothiazole, carbamates, and thiurams.
What is the diagnostic test for rubber-related dermatitis?
The diagnostic test is patch testing.
What are the diagnostic criteria for Baboon syndrome (SDRIFE)?
Diagnostic criteria include exposure to a systemically administered drug, sharply demarcated erythema of the gluteal/perianal area, involvement of at least one other intertriginous/flexural localization, symmetry of affected areas, and absence of systemic signs or symptoms.
What are common allergens in rubber-related dermatitis?
Common allergens include mercaptobenzothiazole, carbamates, thiurams, black rubber mix, and mixed dialkyl thioureas.
What is the recommended diagnostic approach for generalized dermatitis?
The recommended diagnostic approach is patch testing.
What are common allergens associated with generalized dermatitis?
Common allergens include preservatives, fragrances, propylene glycol, cocamidopropyl betaine, ethyleneurea melamine formaldehyde, and corticosteroids.
What metal allergen is most likely responsible for dermatitis on the neck after wearing a necklace?
The most likely metal allergen is nickel.
Its presence can be detected using a spot test containing dimethylgloxime, which produces a pink precipitate.
What is the significance of the Atomizer sign in allergic contact dermatitis?
The Atomizer sign indicates the appearance of a dermatitic plaque on the neck due to the repeated application of fragrances, which can lead to sensitization and elicitation of allergic contact dermatitis (ACD).
What are the stages of allergic contact dermatitis syndrome?
The stages of allergic contact dermatitis syndrome are:
Stage | Description |
|——-|————-|
| Stage 1 | Localized allergic contact dermatitis |
| Stage 2 | Regional dissemination of allergic contact dermatitis |
| Stage 3A | Generalized or distant involvement of allergic contact dermatitis |
| Stage 3B | Systemic exposure resulting in systemic contact dermatitis |
What is the role of patch testing in diagnosing chronic hand dermatitis?
Patch testing is crucial in diagnosing chronic hand dermatitis as it helps identify specific allergens responsible for the dermatitis.
What percentage of the general population is allergic to fragrances?
4% of the general population is allergic to fragrances, commonly affecting the face and hands, behind the ears, and the neck and axillae.
What is the gold standard for identifying allergens in allergic contact dermatitis?
The gold standard for identifying allergens is patch testing, specifically using the T.R.U.E. test with commercially available standardized allergens.
What are the common causes of allergic reactions to topical antibiotics like Neomycin and Bacitracin?
Neomycin is an aminoglycoside used for skin, ear, and eye infections, with 1% of the general population allergic. Bacitracin is used for postoperative care and can cause urticaria and anaphylaxis.
What is the clinical significance of hand involvement in allergic contact dermatitis?
Hand involvement is strongly predictive of a negative impact on quality of life in patients with allergic contact dermatitis.
What are the first-line treatments for acute allergic contact dermatitis?
The first-line treatment for acute allergic contact dermatitis is topical corticosteroids for 2 to 3 weeks.
What complications can arise from patch testing for allergic contact dermatitis?
Complications from patch testing can include itching at the test site, postinflammatory pigmentary changes, infections, scarring, persistent reactions, and rarely, anaphylaxis.
What is the role of para-phenylenediamine in allergic contact dermatitis?
Para-phenylenediamine is a common allergen found in permanent hair dyes, often causing dermatitis on thinner skin areas like the face, eyelids, and neck.
What is the significance of irritant and allergic patterns in patch testing reactions?
Irritant patterns are characterized by a decrescendo reaction, while allergic patterns show a crescendo reaction, indicating the severity and type of allergic response.
What allergen is likely responsible for dermatitis in a patient with a history of stasis dermatitis after using a topical antibiotic?
The likely allergen is neomycin.
The prevalence of neomycin allergy in the general population is 1%.
What allergens should be considered for a patient with dermatitis on the hands after frequent glove use?
Allergens to consider include accelerators and vulcanizing chemicals such as carbamates, mercaptobenzothiazole, and thiuram.
What type of gloves can be safely used for patients with rubber-related dermatitis?
Vicryl gloves can be safely used.
What allergen group is most likely responsible for dermatitis on the face after using a new cosmetic product?
The most likely allergen group is fragrances.
What patch test groups can screen for fragrance allergens?
Patch test groups for screening include M. pereirae, fragrance mix I, and fragrance mix II.
What allergen is most likely responsible for dermatitis on the scalp after using a hair dye?
The most likely allergen is para-phenylenediamine (PPD).
ACD to PPD often spares the scalp while presenting as dermatitis on thinner skin of the face, eyelids, and neck.
What allergen group should be considered for a patient with dermatitis on the hands after frequent use of hand sanitizers?
The allergen group to consider is preservatives, such as formaldehyde releasers.
What is the diagnostic test for preservatives in allergic contact dermatitis?
The diagnostic test is patch testing.
What allergen group should be suspected for dermatitis on the lips after using a new flavored lip balm?
The allergen group to suspect is fragrances.
What is the diagnostic test for fragrance allergens in allergic contact dermatitis?
The diagnostic test is patch testing.
What common allergens are associated with allergic contact dermatitis (ACD) from personal care products?
Common allergens include:
- Methylchloroisothiazolinone/Methylisothiazolinone (MCI/MI): Found in creams, lotions, and wipes; can cause allergic reactions.
- Fragrances: 4% of the population is allergic; affects face, hands, and neck.
- Neomycin: Used for infections; 1% of the population is allergic, especially those with damaged skin.
- Para-Phenylenediamine (PPD): Found in hair dyes; can cause dermatitis on thinner skin areas.
- Rubber: Latex allergies are common, often due to vulcanizing chemicals.
- Topical Steroids: Can cause reactions due to components other than the steroid itself.
How does patch testing help in identifying allergens in patients with suspected allergic contact dermatitis?
Patch testing is the gold standard for identifying allergens. It involves a closed test protocol, repeat open application test, and semiopen patch test.
What are the clinical implications of allergic contact dermatitis on a patient’s quality of life?
Allergic contact dermatitis (ACD) significantly impacts quality of life through pain and itching, embarrassment, work interference, sleep difficulties, and hand involvement.
What management strategies are recommended for patients with allergic contact dermatitis?
Management strategies include identification and avoidance of the offending allergen, acute treatment with topical corticosteroids, and severe cases may require a tapering regimen of oral prednisone.
What are the diagnostic clues for differentiating between irritant contact dermatitis and allergic contact dermatitis?
- Irritant Contact Dermatitis (ICD): Generally, there is an absence of vesiculation and burning exceeds itching. It does not spread beyond the area of contact.
- Allergic Contact Dermatitis (ACD): Distribution of skin findings can be helpful; worsening disease can indicate new contact allergy development.
What are the diagnostic clues for Atopic Dermatitis (AD)?
- Atopic Dermatitis (AD): Distribution of skin findings can be helpful; worsening disease can indicate new contact allergy development.
What are the characteristics of Nummular Dermatitis (ND) in the differential diagnosis of allergic contact dermatitis?
- Nummular Dermatitis (ND): Widespread ACD can assume this pattern; the classical morphology of coin-shaped, well-demarcated plaques favors ND.
How can Seborrheic Dermatitis be identified in the differential diagnosis of allergic contact dermatitis?
- Seborrheic Dermatitis: Characterized by greasy and scaly patches, often affecting the scalp and face.
What are the characteristics of Nummular Dermatitis (ND) in the differential diagnosis of allergic contact dermatitis?
Widespread ACD can assume this pattern in certain patients; nonetheless, the classical morphology of coin-shaped, well-demarcated plaques on the legs, dorsal hands, and extensor surfaces favors ND.
How can Seborrheic Dermatitis be identified in the differential diagnosis of allergic contact dermatitis?
Characterized by greasy and scaly papulosquamous plaques usually located in the hair-bearing regions, scalp, and nasolabial folds.
What are the diagnostic features of Asteatotic Eczema in the context of allergic contact dermatitis?
Presents as parchment-like patches with no edema or vesiculation on the lower legs. May have appearance of river bed.
What are the distinguishing features of Stasis Dermatitis in the differential diagnosis of allergic contact dermatitis?
Characterized by papulosquamous plaques with dyschromia located on the shins and medial surfaces of the lower legs, with presence of concomitant varicosities.
What are the diagnostic clues for Pompholyx and/or dyshidrotic eczema in the context of allergic contact dermatitis?
Deep-seated vesicles on palms, soles, sides of the fingers, and volar edges. When it presents in its classic form, diagnosis can be straightforward; however, when the lesions are few and limited to the hands and/or feet, differentiation can be more difficult.
What are the characteristics of Mycosis Fungoides (MF) in the differential diagnosis of allergic contact dermatitis?
Well-demarcated, atrophic, psoriasiform, scaly patches and plaques of MF are usually found in non-sun-exposed areas of the skin, such as the trunk, breasts, hips, and buttocks (bathing suit distribution).
What are the distinguishing diagnostic clues for differentiating between irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD)?
Physical findings can be indistinguishable from ACD; however, there is an absence of vesiculation, and symptoms are often limited to the area of contact with the irritant.
Symptoms of ACD may include vesiculation and can spread beyond the area of contact, indicating an allergic reaction.
How can atopic dermatitis be differentiated from allergic contact dermatitis based on distribution of skin findings?
Distribution of skin findings can be helpful; patients may develop contact allergies, and worsening disease can indicate new contact allergy development.
Typically presents with localized reactions that may not follow the same distribution as atopic dermatitis.
What are the key diagnostic clues for identifying nummular dermatitis in the context of allergic contact dermatitis?
Widespread ACD can mimic nummular dermatitis, particularly in certain patients. The classical morphology includes coin-shaped, well-demarcated plaques on the legs, dorsal hands, and extensor surfaces, which favors nummular dermatitis over ACD.
What are the distinguishing features of seborrheic dermatitis compared to allergic contact dermatitis?
Characterized by greasy and scaly papulosquamous plaques, typically located in the hair-bearing regions such as the scalp, nape, and nasolabial folds.
Allergic Contact Dermatitis usually presents with localized vesicular or eczematous lesions in response to allergens, not typically greasy in appearance.
How can stasis dermatitis be differentiated from allergic contact dermatitis based on clinical presentation?
Presents with papulosquamous plaques with dyschromia located on the shins and medial surfaces of the lower legs, often associated with venous insufficiency.
Allergic Contact Dermatitis typically presents with localized vesicular lesions in response to specific allergens, not necessarily associated with venous issues.
