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Contact dermatitis. Localized inflammatory response of the skin caused by contact with an irritant Most common form of eczema, occurring to some extent in everyone Severity varies, children and elders are more vulnerable since lower threshold for skin irritation. Eczema. - PowerPoint PPT Presentation
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Contact dermatitisContact dermatitis
Localized inflammatory response of the skin caused by contact with an irritant
Most common form of eczema, occurring to some extent in everyone
Severity varies, children and elders are more vulnerable since lower threshold for skin irritation
EczemaEczema
Also known as dermatitis Acute -vesicles, bullae, crust, erythema
and pruritis Subacute-crust, eythema and pruritis Chronic- lichenification, pruritis,
hyper/hypopigmentation
EczemaEczema
Exogenous Endogenous
EczemaEczema
Exogenous• allergic• irritant
EczemaEczema
Endogenous-
– Asteatotic-dry irritable skin of elderly
– Nummular- acral, coin shaped
– Dyshidrotic-vesicular of palms/soles
– Seborrheic- sebaceous areas
– Stasis-associated with venous stasis
– Atopic
Contact DermatitisContact Dermatitis
Pathophysiology- An adaptive response designed to clear irritant usually results in mild inflammation. With cell mediated it can worsen and extend to adjacent areas.
Allergic Contact DermatitisPathogenesis
Sensitization (Induction)--1o exposureContact allergen usually a hapten
–LMW, links with endogenous proteinPicked up by LC’s and presented to
naïve T-cells in lymph nodeCLA upregulated on activated T-cellsSpecific effector T-cells home to skin
Often nothing happens…Why?
Allergic Contact DermatitisPathogenesis
Elicitation--subsequent exposuresAllergen taken up by DC’sMemory T-cells recognize Ag:MHC
complex in situ (in the skin)T-cells proliferate in situ
–IL-2, TNF, IFN- expressedInflammatory response ensuesQuestion: What turns this process off?
Allergic Contact DermatitisImmunopathology
Th1Th1
Th2Th2
Th0Th0
IL-2IL-2
TNFTNF
IFNIFN
IL-4IL-4
IL-5IL-5
IL-10IL-10
Cell-mediated immunityCell-mediated immunity
Humoral immunityHumoral immunity
IL-12IL-12
IL-10IL-10
IL-12, IFNIL-12, IFN
IL-4IL-4
Contact Dermatitis Irritant vs. Allergic
More commonReaction minutes to
hours after 1st contact
Direct cellular injury by chemical
No immunologic memory
Less commonNo or delayed
reaction after 1st contact
Ag presented to T- cells
Immunologic memory
Allergen Patch Test KitAntigen Source Group of substances associated with contact dermatitis, such as benzocaine, phenylenediamine, lanolin, neomycin, epoxy resins, etc.Dosage and RouteApply from 1 to 20 allergens as a test battery to a patch test device; TopicalIndicationsFor accessment of contact dermatitisAdverse ReactionsMild and localized to the site, anaphylaxis rareEfficacy22% false positives
Contact DermatitisContact Dermatitis
Treatment and Prognosis
– Avoidance
– Symptomatic TX-Avenue bath, Burrow's son
– Antihistamines
– Corticosteroid creams and ointment
– Skin rash resolves in short time 1-3 weeks
Oral DesensitizationOral Desensitization
Antigen SourceLeaf extracts from ToxicodendronDosage and RouteDaily ingestation of gradually increasing amounts of extract.
Treatment should be started only when the patient is free of skin rash; oral
IndicationsFor prevention of contact dermatitis, also called poison ivy or
poison oak dermatitis.Adverse ReactionsPruritus ani (a burning sensation in the rectum) occurs briefly
during the first weeks.EfficacyAdequately potent as judged by the FDA
