CONTACT DERMATITIS
Contact
dermatitis (dermatitis venenata), a type IV delayed hy-persensitivity reaction,
is an acute or chronic skin inflammation that results from direct skin contact
with chemicals or allergens. There are four basic types: allergic, irritant,
phototoxic, and photoallergic (Table 53-4). Eighty percent of cases are due to
excessive exposure to or additive effects of irritants (eg, soaps, detergents,
organic solvents) (Tierney et al., 2001). Skin sensi-tivity may develop after
brief or prolonged periods of exposure, and the clinical picture may appear
hours or weeks after the sen-sitized skin has been exposed.
Symptoms
include itching, burning, erythema, skin lesions (vesi-cles), and edema,
followed by weeping, crusting, and finally dry-ing and peeling of the skin. In
severe responses, hemorrhagic bullae may develop. Repeated reactions may be
accompanied by thickening of the skin and pigmentary changes. Secondary
inva-sion by bacteria may develop in skin abraded by rubbing or scratching.
Usually, there are no systemic symptoms unless the eruption is widespread.
The
location of the skin eruption and the history of exposure aid in determining
the condition. In cases of obscure irritants or an unobservant patient, however,
diagnosis may be extremely diffi-cult, often involving many trial-and-error
procedures before the cause is determined. Patch tests on the skin with
suspected of-fending agents may clarify the diagnosis.
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