Poisonous spiders are endemic in the tropics and the southern hemisphere where they typically inhabit woodpiles, outhouses and dark corners of garages and houses. Localized pain, swelling and erythema occur within 30 minutes of the bite. Abdominal cramps, which may simulate an acute condition requiring immediate surgery, are an indication of dissemination of the venom. In severe cases, intense localized pain and vasoconstriction can be followed by oedema and local necrosis. Complications, which are often fatal, include acute haemolysis, pulmonary oedema and renal insufficiency.

Prevention and management

Indoor spraying with pyrethroids is highly effective as a control measure. After being bitten, the patient should remain as still as possible, since movement accelerates dissemination of the venom. Specific antivenoms are of value when the species of spider is known. Otherwise, analgesics and muscle relaxants should be given to relieve pain and muscular spasms. Oral corticosteroids, if administered within 24 hours of the attack, are claimed to reduce the risk of local necrosis and the incidence of disfiguring scars.