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What Is the Neurotoxin in the Black Widow?

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The black widow spider’s venom is 15 times more toxic than a rattlesnake's. Five neurotoxins -- alpha, beta, gamma, delta and epsilon latroinsectotoxins -- target only other insects. Another neurotoxin, called alpha latrocrustatoxin, affects crustaceans like shrimp, lobster and crabs. One other neurotoxin, the extremely potent alpha latrotoxin, specifically poisons animals that have backbones. This alpha latrotoxin is the one you need to be concerned about.

What Does Alpha Latrotoxin Do?

Alpha latrotoxin is a poisonous protein that targets the central nervous system by changing the structure and function of the nerve terminals. According to Davidson College, the neurotoxin also damages cellular communication by interfering or destroying signals between nerves that control the body’s muscles. It triggers rapid exocytosis – when the nerve cells eject calcium, waste and excess chemical transmitters – so the affected cells dump all at once and can no longer communicate.

How Does It Affect You?

Most of the time, people are unaware that they’ve been bitten -- the black widow’s fangs are tiny. When it's felt, it usually feels like two minor pin pricks. Your reaction to the neurotoxin is dependent on how sensitive you are to alpha latrotoxin, how much venom was injected, where you were bitten, your age and your overall health. The neurotoxin goes to work immediately; pain can set in a few minutes later or hours later. According to eMedicineHealth.com, symptoms to look for are muscle cramps and pain, severe back and arm pain, weakness and shakiness, abdominal pain, nausea or vomiting, fainting, dizziness, elevated blood pressure and heart rate, chest pain and breathing problems. The abdominal pain often resembles that of a gall bladder attack or appendicitis, while chest pains often mimic those of heart attacks.

Rare Effects of Black Widow Neurotoxins

Black widow neurotoxin seldom has a serious effect on humans. The University of Tennessee Agricultural Extension Service website says less than 5 percent of black widow bites result in death. However, heart damage is a rare medical reaction from alpha latrotoxin. One man who was bitten by a black widow spider developed a critical heart condition requiring mechanical ventilation and a lengthy hospital stay, according to “Case Reports in Medicine."


Critical reactions to alpha latrotoxin require immediate medical intervention and sometimes hospitalization. Have bites checked out by a medical professional to rule out severe complications. If you are bitten by a black widow, keep calm to minimize the venom's spread. Ice applied to the bite area will reduce swelling and pain. Your doctor will give you antivenin if you exhibit extreme sensitivity to the neurotoxin and medication to relieve the pain.