Human Stratum Corneum Penetration by Nickel In vivo Study of Depth Distribution after Occlusive Application of the Metal as Powder

Sequential tape stripping was implemented on three healthy In the present context, the term ‘ ‘ stratum corneum penetravolunteers to examine the surface distribution of nickel through tion’ ’ is used to indicate exogenous material found in the SC, human stratum corneum in vivo following occlusive application in contrast to the term ‘ ‘ dermal absorption’ ’ , which denotes of the metal as powder on the volar forearm. Exposure sites permeant that potentially becomes available systemically. were stripped 20 times at intervals from 5min to 96h post- Despite many investigations into the behavior of nickel in dosing and the strips analyzed for metal content by Inductively contact with the skin, questions relative to its mode of action Coupled Plasma-Mass Spectroscopy with a detection limit for remain unanswered. One paradox in the behavior of nickel nickel of 0.5ppb. The gradients of nickel distribution proe les became apparent when it was investigated for skin di Vusivity. increased proportionally with occlusion time, but after the 10th In in vitro tests with human skin, permeability coe Ycients for strip to the 20th strip continued at constant levels. Total nickel water-soluble inorganic nickel salts were measured in the range removed with 20 stratum corneum strips to the level of the 10O 6 to 10O 4 cm/h, with lag times of up to 90h preceding the glistening layer after maximumocclusion of 96h was 41.6 lg/cm2 appearance of the permeant in the acceptor phase (20‐ 24). (± 12.2; average n =3). In order to normalize the nickel depth This is diYcult to reconcile with the phenomenon that even distribution proe les, stratum corneum removed by stripping of contact of intact skin with nickel-releasing metallic objects untreated skin after occlusion was determined by weighing. may elicit dermatitis in those allergic to the metal (25‐ 28). Following application of nickel dust over 24h, analysis of the Oxidation of nickel in sweat has been investigated repeatedly 20th strip still indicated nickel present at 1.42 lg/cm2 (± 0.68; (29‐ 34) and appears to be an important factor in the pathogenaverage n =3). These data indicate that, in contact with skin, esis of nickel allergy. Released with sweat are chloride ions, nickel metal is oxidized to form soluble, stratum corneum- butyric, pyruvic and lactic acid (35‐ 37). Furthermore, the diVusible compounds which may penetrate the intact stratum acid mantle of the skin contains urocanic and pyrrolidone corneum, presumably by the intercellular route, and have the carboxylic acid (38, 39), as well as fatty acids, primarily oleic potential to elicit allergic reactions. Key words: adsorption; and linoleic (40‐ 43). These compounds are likely to solubilize allergy; contact dermatitis; human; inductively coupled plasma, metal in amounts apparently su Ycient to elicit an allergic mass spectroscopy; in vivo; metal; nickel; shunt di Vusion; reaction when a nickel-alloy coin is taped to the skin of highly stratum corneum; tape stripping .