• colchicine;
  • humans;
  • irritants;
  • mitosis;
  • patch tests;
  • skin

Studies on how irritant materials might induce epidermal hyperplasia were initiated by investigating their influence on epidermal mitosis. 5 % hydrochloric acid, neat dimethyl acetamide and 1 % benzalkonium chloride had no effect. 5 % benzalkonium chloride, however, produced a 10-fold increase in mitotic activity, while a dose response curve was seen with sodium lauryl sulphate (SLS) peaking at 1 %, 1 % SLS produced a remarkably uniform response for this type of assay and it is suggested that it might provide a useful model for situations of increased epidermal cell turnover such as psoriasis. It is also noted that there was apparently no direct relationship between gross inflammation and the mitotic response.