Spider Bite FAQ

Kyoto: Hiking from Kibune to Kurama

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The brown, or violin, spider (Loxosceles recluse) more recently labeled the "brown recluse spider," has received attention as the cause of "necrotic arachnidism." Following the bite of this spider, a blister appears, and is surrounded by an area of intense inflammation about one-half inch (1.25 cm) in diameter. Pain is mild at first but may become quite severe within about eight hours. Over the next ten to fourteen days the blister ruptures and the involved skin turns dark brown or black. Eventually the dead, black tissue drops away, leaving a crater that heals with scarring.

A few individuals have large skin losses that require grafts to cover the defect. Some children have lost considerable portions of the face. Such events have attracted great notoriety for this spider, even though much smaller wounds are far more typical. Bites are attributed to Loxosceles recluse (incorrectly) well outside of its habitat, which is limited to the southeastern and south-central portion of the United States and ends at the Texas-New Mexico border. Generalized symptoms that may appear within thirty-six hours of the bite include chills and fever, nausea and vomiting, joint pain, and a skin rash or hives. With severe reactions, red blood cells are broken down (hemolysis) and platelets are destroyed (thrombocytopenia), which can result in significant anemia and bleeding tendency. Rare fatalities have occurred, mostly in children.

Essentially nothing can be done for such bites in a wilderness situation unless appropriate injectable medications are carried along. If the person can be hospitalized within less than eight hours, the site of the bite can be surgically excised. Such therapy should be reserved for bites from spiders clearly identifiable as L. recluse, so the spider must be captured (intact if possible) and brought to the hospital to be identified. After eight hours the area involved may be too large to be excised. Corticosteroids may also be administered. One recommended program is 4 mg of dexamethasone, administered intramuscularly every six hours until the reaction starts to subside, and then in tapered doses. Others include injection of hydrocortisone beneath the bite and the administration of dapsone. Nothing is very satisfactory.