The black widow spider produces a protein venom that affects the victim's nervous system. Some people are slightly affected by the venom, but others may have a severe response. The first symptom is acute pain at the site of the bite though there may only be a minimal local reaction.

The local pain may be followed by localized or generalized severe muscle cramps, abdominal pain, weakness, and tremor. In severe cases, nausea, vomiting, faintness, dizziness, chest pain, and respiratory difficulties may follow.

The severity of the reaction can depend on the age and physical condition of the person bitten. Children and the elderly are more seriously affected than young adults. Read more about the symptoms and treatments for black widow spider bites.