chapter  13
Diagnostic Tests for Type IV or Delayed Hypersensitivity Reactions
ByDavid E. Cohen, Ronald R. Brancaccio, Nicholas A. Soter
Pages 20

Contact dermatitis accounts for more than 90% of all occupational skin diseases and is one of the most important occupational illnesses affecting American workers (1). Contact dermatitis comprises two distinct in ammatory processes caused by adverse exposure of the skin: irritant and allergic contact dermatitis. These syndromes have indistinguishable clinical characteristics. Classically, erythema (redness), induration (thickening and rmness), licheni cation (accentuation of skin folds), scaling ( aking), and vesiculation (blistering) are present on areas

is a mixed-cell in ammatory in ltrate of lymphocytes and eosinophils and the hallmark nding of spongiosis, epidermal intercellular edema. These histopathological features are not suf cient to differentiate allergic from irritant contact dermatitis, atopic dermatitis, and many other eczematous dermatitides, although there are subtle differences in the in ammatory responses (2). Because their etiology is different, the two syndromes are presented separately.