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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 subtypes of irritant contact dermatitis, and describe them.

ICD can be divided into acute toxic and cumulative insult subtypes. Acute toxic eruptions occur from a single exposure to a strong toxic chemical, such as an acid or alkali, inducing erythema, vesicles, bullae, or skin sloughing. Reactions occur within minutes to hours after exposure, localize to the areas of maximal contact, and have sharp borders. In most cases, healing occurs soon after exposure. Chronic cumulative insult reactions are the more common type of ICD. These are due to multiple exposures of many low-level irritants, such as soaps and shampoos, over time. This dermatitis may take weeks, months, or even years to appear. It is characterized by erythema, scaling, fissuring, pruritus, lichenification, and poor demarcation from the surrounding skin.

Przybilla B, Rueff F: Contact dermatitis. In Burgdorf WH, Plewig G, editors: Braun-Falco’s dermatology, ed 3, Heidelberg, 2009, Springer, pp 377–401.