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Contact Dermatitis

»	Name the two pathogenic types of contact dermatitis.
»	Name the two subtypes of irritant contact dermatitis, and describe them.
»	Explain the pathogenesis of allergic contact dermatitis (ACD).
»	Can urticarial reactions occur from contact with a substance?
»	Why is the distribution of a contact dermatitis rash important?
»	List three common misperceptions regarding the location of a contact dermatitis.
»	How is patch testing done?
»	What substances are tested in the standard “screening” patch test?
»	An astute physician should not need to patch test. Right?
»	What is a repeated open application test (ROAT)?
»	What is the differential diagnosis of contact dermatitis?
»	Which is the most common allergen on the standard tray?
»	Is nickel the most common allergen overall?
»	If a change in a skin care product does not lead to clearing of a patient’s rash, does this mean that the original product was not the culprit?
»	How is contact dermatitis managed?

Name the two pathogenic types of contact dermatitis.

Contact dermatitis refers to cutaneous inflammation resulting from the interaction of an external agent and the skin. These reactions occur through one of two mechanisms: a nonimmunologic irritant contact dermatitis (ICD) or an immunologic allergic contact dermatitis (ACD). ICD accounts for 80% of all reactions, while ACD is responsible for approximately 20%. Although over 3700 substances have been identified as contact allergens, almost any substance, under the right circumstances, can act as an irritant. It is important to note that irritating compounds can be allergenic, and allergenic compounds can be irritating.

Marks JG, Elsner P, DeLeo VA: Contact and occupational dermatology, ed 3, St Louis, 2002, Mosby.