[3] Symptoms may include pain which may be at the bite or involve the chest and abdomen, sweating, muscle cramps and vomiting among others.

[1] 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.

[1] Most spider bites are managed with supportive care such as nonsteroidal anti-inflammatory drugs (including ibuprofen) for pain and antihistamines for itchiness.

[6] While an antivenom exists for black widow spider venom, it is associated with anaphylaxis and therefore not commonly used in the United States.

In the Middle Ages a condition claimed to arise from spider bites was tarantism, where people danced wildly.

[10] Activation of the sympathetic nervous system can lead to sweating, high blood pressure and gooseflesh.

[22] Medically significant spider venoms include various combinations and concentrations of necrotic agents, neurotoxins, and pharmacologically active compounds such as serotonin.

Unlike snake and scorpion envenomation,[23] widow and recluse species bites rarely have fatal consequences.

Heart muscle damage is an unusual complication of widow venom that may lead to death.

[25] Pulmonary edema, which is fluid accumulation in the lungs, is a feared and potentially serious but uncommon complication of funnel-web venom.

Recluse venom may also cause severe hemolysis (destruction of red blood cells), though this is typically uncommon.

[4] An affected person may think that a wound is a spider bite when it is actually an infection with methicillin-resistant Staphylococcus aureus (MRSA).

[29] False reports of spider bites in some cases have led to misdiagnosis and mistreatment, with potentially life-threatening consequences.

Treatment of bites may depend on the type of spider; thus, capture of the spider—either alive, or in a well-preserved condition, is useful.

[33][34] Treatment of spider bites includes washing the wound with soap and water and ice to reduce inflammation.

[35] Black widow post-envenomation treatment seeks to control resulting pain and nausea.

[4] Recommendations to limit the extent of damage include elevation and immobilization of the affected limb, application of ice.

Many therapies have been used including hyperbaric oxygen, dapsone, antihistamines (e.g., cyproheptadine), antibiotics, dextran, glucocorticoids, vasodilators, heparin, nitroglycerin, electric shock, curettage, surgical excision, and antivenom.

South Africa also has six-eyed sand spiders (Hexophthalma species), whose bite may potentially cause skin necrosis.

[46][10] In Switzerland about ten to one hundred spider bites occur per one million people per year.

[48] The American Association of Poison Control Centers reported that they received calls regarding nearly 10,000 spider bites in 1994.

[49] The native habitat of brown recluse spiders is in the southern and central United States, as far north as Iowa.

Encounters with brown recluse outside this native region are very rare and bites are thought to be suspect.

[citation needed] Wild dancing and music was the cure for tarantism—the frenzy was believed to arise from the bite of a spider.