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A spider bite, also known as arachnidism, is an injury resulting from the bite of a spider. The effects of most bites are not serious. Most bites result in mild symptoms around the area of the bite.〔 Rarely they may produce a necrotic skin wound or severe pain. Most spiders do not cause bites that are of importance.〔 For a bite to be significant, substantial envenomation is required. Bites from the widow spiders involve a neurotoxic venom which produces a condition known as latrodectism. Symptoms may include: pain which may be at the bite or involve the chest and abdomen, sweating, muscle cramps and vomiting among others.〔 Bites from the recluse spiders cause the condition loxoscelism, in which local necrosis of the surrounding skin and widespread breakdown of red blood cells may occur. Headaches, vomiting and a mild fever may also occur.〔 Other spiders that can cause significant bites include: the Australian funnel web spiders and the South American wandering spider.〔 Efforts to prevent bites include clearing clutter and the use of pesticides.〔 Most spider bites are managed with supportive care such as NSAIDs (including ibuprofen) for pain and antihistamines for itchiness.〔 Opioids may be used if the pain is severe.〔 While an antivenom exists for black widow spider venom it is associated with anaphylaxis and therefore not commonly used in the United States.〔 Antivenom against funnel web spider venom improves outcomes.〔 Surgery may be required to repair the area of injured skin from some recluse bites. Spider bites may be overdiagnosed or misdiagnosed.〔 Historically a number of conditions were attributed to spider bites. In the Middle Ages a condition claimed to arise from spider bites was tarantism, where people danced wildly. While necrosis has been attributed to the bites of a number of spiders, good evidence only supports this for recluse spiders.〔 ==Signs and symptoms== Almost all spiders are venomous, but not all spider bites result in the injection of venom. Pain from non-venomous, so-called "dry bites" typically lasts for 5 to 60 minutes while pain from envenomating spider bites may last for longer than 24 hours. Bleeding also may occur with a bite. Signs of a bacterial infection due to a spider bite occur infrequently (0.9%).〔 A study of 750 definite spider bites in Australia indicated that 6% of spider bites cause significant effects, the vast majority of these being redback spider bites causing significant pain lasting more than 24 hours. Activation of the sympathetic nervous system can lead to sweating, high blood pressure and gooseflesh. Most recluse spider bites are minor with little or no necrosis. However, a small number of bites produce necrotic skin lesions. First pain and tenderness at the site begin. The redness changes over 2 to 3 days to a bluish sinking patch of dead skin—the hallmark of necrosis. The wound heals slowly over months but usually completely. and, rarely, widespread symptoms, including profound anemia. Rarely the bite may also produce the systemic condition with occasional fatalities 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spider bite」の詳細全文を読む スポンサード リンク
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