This study aimed to evaluate the mode of action of a new dressing, KerraLite Cool®. KerraLite Cool was shown to inhibit the pro- and activated forms of the matrix metalloproteinase MMP-2 and MMP-9 in vitro. In the corresponding clinical investigations involving 11 patients with venous or mixed aetiology leg ulcers, visible signs of improvement were apparent after 14 days treatment in all subjects. KerraLite Cool exerts a marked protease inhibitory activity that may be effective under physiological conditions. The mechanism of inhibition appears to be a combination of modifying the ionic environment and selective protease depletion. Clinical work with KerraLite Cool consistently points to a significant reduction in wound pain and the stimulation of stalled wounds.