Chapter 4: Contact Dermatitis and Patch Testing Flashcards
What is contact dermatitis
And eczematous dermatitis caused by exposure to substances in the environment
– May cause acute, subacute, or chronic eczematous inflammation
What is the most common cause of contact dermatitis
Irritation of the skin
– Repeated use of strong alkaline soap or industrial exposure to organic solvents extract lipids from the skin.
How do you manage irritant contact dermatitis
- Avoid exposure to irritants
- Topical steroids are used initially
- Moisturizers used generously and frequently
- Barrier creams
- Cold compresses a use for acute inflammation.
- Hands should be washed in cool or tepid water
- Repeated low-level UV exposure may be effective for long-term persistent cases.
- Even after the skin appears normal it takes approximate four months or more for barrier function to normalize
What are the two phases associated with allergic contact dermatitis
- Sensitization phase
2. Elicitation phase
What is the sensitization phase of allergic contact dermatitis
Antigen is applied to the skin surface, penetrates the epidermal barrier, it is taken up by the Langerhans cells in the epidermal basal layer
– the Langerhans cell migrates to the regional lymph nodes and presents the antigen to the T lymphocyte.
What is the elicitation phase of allergic contact dermatitis
Occurs in sensitized patients with re-exposure to the antigen.
– This interaction results in cytokine induced activation and proliferation of the antigen specific T lymphocytes and the release of inflammatory mediators
What is cross sensitization
An allergen, the chemical structure of which is similar to that of the original sensitizing antigen, may cause inflammation because the immune system is unable to differentiate between the original and the chemically related antigen
What is systemic contact dermatitis
Results from the exposure to an allergen by ingestion, inhalation, ingestion or percutaneous penetration in a person previously sensitized to the allergen by cutaneous contact
What is the most important clue to the cause of an allergen
The shape and location of the rash
– The scalp, palms, and soles are resistant to allergic contact dermatitis and may show only minimal inflammation despite contact with an allergen that produces dermatitis and adjacent areas.
The failure of an eczematous dermatitis to respond to standard treatments suggest what
Suggests that the dermatitis is allergic and not irritant
How can you determine the intensity of the inflammation and degree of sensitivity
The location and duration of inflammation
– Acute inflammation appears as macular erythema, edema, vesicles, bullae
– Chronic inflammation is characterized by lichenification, scaling, or fissures.
How prevalent is allergic contact dermatitis in children
Allergic contact dermatitis may account for as many as 20% of all cases of dermatitis in children
What is the management of allergic contact dermatitis
- Minimize products for topical use.
- Use ointments instead of creams (creams contain preservatives and are complex mixtures of chemicals)
- Botanical extracts may be used in “fragrance free” products
- When patch testing, also test the patient’s consumer products.
- Read product labels carefully.
What is rhus dermatitis
Allergens responsible for poison ivy and poison oak allergic contact dermatitis are contained within the resinous sap material terms urushiol
urushiol is composed of a mixture of catechols
What are the characteristic lesions of a rhusdermatitis
Linear lesions created when part of the plant is drawn across the skin or from streaking the oleoresin while scratching
– Quickly as eight hours after contact or may be delayed for one week or more
Do blister fluids contain the oleoresin and a rhusdermatitis
No, furthermore blistered Fluid can not spread the inflammation
What can be done to prevent the spread of a rhusdermatitis
Washing the skin with any type of soap and inactivates and removes all surface oleoresin
After 10 minutes, only 50% of the urushiol can be removed; after 30 minutes, only 10% can be removed; and after 60 minutes none can be removed
What is the treatment of acute inflammation with rhus dermatitis?
blisters and intense erythema are treated with cold, wet compresses, and they are highly effective during the acute blistering stage.
Calamine lotion controls itching but prolonged use causes excessive drying.
How is severe poison ivy treated
Prednisone, administered in a dosage of 20 mg twice each day for at least seven days
What are the three types of reactions to natural rubber latex (NRL)
irritant contact dermatitis
Allergic contact dermatitis
immediate-type hypersensitivity reaction
What is irritant contact dermatitis from natural rubber latex
A non immune eczematous reaction caused by moisture, heat, and friction under gloves
What is allergic contact dermatitis (type IV hypersensitivity)
Latex allergy occurs in up to 10% of operating room nurses.
Delayed type hypersensitivity (type IV) is a T-cell-mediated sensitization to rubber accelerators and antioxidants and latex gloves causes an allergic contact dermatitis usually limited to the sites of the direct contact
-Once sensitized, subsequent challenges from the same allergen will cause eczematous dermatitis.
Type IV allergy accounts for about 80% of occupationally acquired rubber allergy.
What is immediate-type hypersensitivity (type I allergy)
IgE mediated reaction requires previous sensitization.
Skin skin exposure causes contact urticaria
Exposure to latex in the air elicits allergic rhinitis, conjunctivitis, asthma, anaphylaxis, and death
Patients with type I NRL allergy can have a cross reaction to certain foods; what are the foods
Banana
avocado
tomato
Kiwi
Or local irritation when working with such food
What is the RAST test
Used to detect specific IgE, such as those with the latex specific allergy
If the patient does not respond to treatment for dermatitis or should be the next step in consideration
Treatment should be patch test to exclude allergy
What is the leading cause of allergic contact dermatitis worldwide
Sensitization to nickel
Just cooking with stainless steel pans provide a source of nickel ingestion
Nope
What is baboon syndrome
Intertriginous drug eruptions
Symmetric eczematous eruptions involving the elbows, axilla, eyelids, and sides of the neck accompanied by bright red anogenital lesions.
What is the most common synthesizer for men in industrialized countries
Chromate
Sources are cemented, photographic processes, metal and dyes
What is cement dermatitis
Severe deep cutaneous alkaline (pH 12) Burns may occur in the lower legs of men whose skin is in direct contact with wet cement.
What is the most common cosmetic allergen
Fragrance
Is it possible to be allergic to topical steroids
Yes
When is patch testing warranted
Cases in which inflammation persist despite avoidance of the offending agent and appropriate topical therapy.
What is an open patch test
The suspected allergen is applied to the skin of the upper outer arm and left uncovered. Application is repeated twice daily for two days
What is the use patch test
Suspected cream or cosmetic is used on a site distant from the original eruption.
the material is applied twice daily for at least seven days. The test is stopped if a reaction occurs
What is a closed patch test
the material is applied to the skin and covered with adhesive bandage. The adhesive bandage is removed in48 hours for the initial interpretation
A negative patch test with this direct technique does not rule out the diagnosis of allergy
How’s a patch test graded
Test reactions are graded: \+ = weak (nonvesicular) \+ + = strong (edematous or vesicular) \+ + + = extreme (spreading, bolus, ulcerative) - = negative reaction IR - irritant reaction
What is the concern with using steroids with patch testing
Corticosteroids such as prednisone in dosages of 15 mg per day or the equivalent may inhibit patch test reaction.
If a patient has been treated with systemic corticosteroids, patch testing should be delayed for at least two weeks
What is excited skin syndrome
(Eczema creates eczema)
Excited skin syndrome is a major cause of false-positive patch test reactions.
