The brown recluse spider (Loxosceles reclusus) is endemic to much of the southern and parts of the eastern United States. The envenomation (bite) may cause extensive necrosis of the skin and underlying soft tissues("dermonecrotic arachnidism"). The venom of the brown recluse is both hemolytic and cytotoxic. There are multiple components, including Sphingomyelinase D and other enzymes (hyaluronidase, deoxyribonuclease, ribonuclease, alkaline phosphatase, and lipase). Arachidonic acid effects, mediated by prostaglandins and the inflammatory neutrophils (part of the host reaction) contribute to the tissue necrosis.