The primary goal of the present research was to determine whether sulfated polysaccharides derived from red microalgae possess antiinflammatory properties when directed against specific parameters of human skin inflammation. These unique biopolymers were studied in both in vitro and in vivo models of skin inflammation. Human subjects were recruited to participate in a study in which the polysaccharide material was applied topically and shown to inhibit cutaneous erythema induced by a known irritant. Leukocyte migration from capillary blood into sites of inflammation is an essential component of the inflammatory process and occurs in a series of steps, two of which are adhesion and chemotaxis. In vitro, the polysaccharide material primarily inhibited the migration of polymorphonuclear leukocytes (PMNs) toward a standard chemoattractant molecule and also partially blocked adhesion of PMNs to endothelial cells. The data obtained strongly suggest that sulfated polysaccharides derived from red microalgae have significant beneficial potential for use in topical products. In addition, the data suggested that the antiinflammatory mechanism for the polysaccharide was, at least in part, due to inhibition of circulating immune cell recruitment toward inflammatory stimuli.