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Symptoms and Signs of Black Widow Spider Bite

Doctor's Notes on Black Widow Spider Bite

The signs and symptoms of the black widow spider bite usually begins with acute pain at the site of the bite. Other symptoms usually start about 20 minutes to one hour after the bite. The bite itself begins with two small dots. Local pain at the bite site is followed by localized general severe muscle cramps, abdominal pain, weakness and/or tremors. Severe signs and symptoms are nausea, vomiting, fainting, dizziness, chest pain and respiratory difficulties. However, people rarely die from a black widow spider bite.

The spider itself is a sign; black widow spiders are black with a reddish hour-glass shape on its body; if the spider can be captured or killed safely, it should be brought to the emergency department and will help identify the bite source.

The cause of the spider bite signs and symptoms is due to a protein venom secreted during the spider bite. Symptoms are severe; antivenin can help reduce symptoms.

Medical Author:
Medically Reviewed on 3/11/2019

Black Widow Spider Bite Symptoms

The black widow spider produces a protein venom that affects the victim's nervous system. This neurotoxic protein is one of the most potent venoms secreted by an animal. 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, although there may only be a minimal local reaction. Symptoms usually start within 20 minutes to one hour after the bite.

  • Local pain may be followed by localized or generalized severe muscle cramps,abdominal pain, weakness, and tremor. Large muscle groups (such as the shoulder or back muscles) are often affected, resulting in considerable pain. In severe cases, nausea, vomiting, fainting, dizziness, chest pain, and respiratory difficulties may follow.
  • The severity of the reaction depends on the age and physical condition of the person bitten. Children and the elderly are more seriously affected than young adults.
  • In some cases, abdominal pain may mimic such conditions as appendicitis or gallbladder problems. Chest pain may be mistaken for a heart attack.
  • Blood pressure and heart rate may be elevated. The elevation of blood pressure can lead to one of the most severe complications.
  • People rarely die from a black widow's bite. Life-threatening reactions are generally seen only in small children and the elderly.

Bad Bugs Identify Bug Bites From Mosquitos, Spiders and More Slideshow

Bad Bugs Identify Bug Bites From Mosquitos, Spiders and More Slideshow

Ticks are often found in plants and brush, and can attach to and bite people and animals. Most tick bites are not harmful; however, ticks can carry serious diseases including Lyme disease and Rocky Mountain spotted fever.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.