 In humans , a bite causes rapid and conspicuous swelling , intense pain , severe shock and local blistering . Other symptoms may include uncoordinated movements , defecation , urination , swelling of the tongue and eyelids , convulsions and unconsciousness . Blistering , bruising and necrosis may be extensive . There may be sudden hypotension , heart damage and dyspnoea . The blood may become incoagulable with internal bleeding that may lead to haematuria and haematemesis . Local tissue damage may require surgical excision and possibly amputation . Healing may be slow and fatalities during the recovery period are not uncommon . 
