Often there is a general sense of discomfort shortly after the bite, and acute symptoms increase in severity during the firs day after a bite. Symptoms usually decline after two to three days but some mild symptoms may continue for several weeks after recovery. Only the bite of the female, usually the adult female, is potentially dangerous. Although extremely painful and temporarily debilitating, fatalities from untreated widow bites are uncommon. During the period between 1926 to 1943, mortality ranged from 4 percent to 5 percent, but current medical treatments have reduced this to a much smaller incidence.
Death usually results from respiratory paralysis.
Prompt medical treatment can greatly reduce the danger from widow bites and has reduced fatalities to extremely low rates in recent years. Because of the possible severity of black widow bites, immediate medical attention is important. Physicians can intravenously inject calcium gluconate to counteract most effects of the toxin. The injection helps bolster levels of calcium salts that are depressed by the effects of the bite. A black widow antiserum also is available, although effects usually are less dramatic than the calcium gluconate treatment.