How do you diagnose and treat the black widow spider bite?

The female black widow spider is 10 to 15 mm long and has a black, globose abdomen, often with a red hourglass figure on the ventral surface. This spider is found in all 48 contiguous states. The venom is a potent neurotoxin.

Initially, the bite may sting slightly and then begins to burn. The skin changes are usually minimal, but the systemic symptoms of pain and muscle cramping may become intense. Diaphoresis, dizziness, anxiety, salivation, and other neurotoxic symptoms may ensue. Treatment of this neurotoxin should be prompt. Antisera are available and afford prompt relief, especially in the very young, old, or those with a history of heart disease or hypertension. Calcium gluconate, muscle relaxants, and pain medications are also used.

Elston DM: What’s eating you? Latrodectus mactans (the black widow spider), Cutis 69:257–258, 2002.