Chitosan based hemorrhage control dressings provide effective external hemorrhage control while having few side effects. Known residual contaminants present in chitosan formulations include endotoxins and proteins known to stimulate gene expression in the liver. This study investigated gene expression in the liver using rat bio-compatibility models to gain knowledge regarding toxicogenetic effects caused by dressing contaminants. Gene chip technology was employed to evaluate effects of subcutaneous dressings on RNA expression in the liver. Various formulations of dressings containing known concentrations of endotoxin and control were evaluated over 8 or 28 days. Comparisons of cohorts suggest no correlation between endotoxin levels in dressings and hepatic gene expression. Additional studies are underway to test correlations between residual protein in dressings and gene expression.