Distribution of nickel and cobalt following dermal and systemic administration with in vitro and in vivo studies.

Contact dermatitis following skin contact with ionic metals occurs in about 15% of the human population, but systemic responses are not as common. It is generally believed that skin contact with metal ions leads to different biological processing compared with systemic contact. The purpose of the experiments presented here was to examine elimination of nickel and cobalt salts following skin application and following injection into the deep tissue of hamsters. In addition uptake of the metal by fibroblasts and by keratinocytes was examined in vitro. The data indicate that elimination of nickel and cobalt in the urine following systemic injection was rapid, as expected, but that elimination following skin application was delayed. Much of the metal was retained in the skin. Uptake of the metal by keratinocytes at low doses was greater than the uptake by the fibroblasts. At high doses the differences were not as great. Thus the conclusion is drawn that metal salts are retained in the skin for an extended period of time and could lead to prolonged antigen processing and consequent immune responses in the dermal tissue. Skin application leads to some systemic distribution but the systemic application did not lead to skin accumulation.