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Black Widow Spider Bite

Black Widow Spider Bite Facts

Of the 30,000 types of spiders, the black widow is probably the one best known and feared. Although spiders are often blamed for all kinds of symptoms, from local itching to diffuse rashes, the fact is that spiders rarely bite humans, and in fact, most spider bites do not even break the skin.

The bites of very large spiders such as tarantulas can be painful. Otherwise, in the temperate regions, the only spiders to be feared are the black widow and the brown recluse.

  • The black widow is a medium-sized spider whose body is about a half-inch long. The name is derived from the mistaken belief that the female invariably kills the male after mating. Although the spider is mostly found in the southern United States, it may be seen throughout the US. Five species are common to the US, with two of them being the most common:
    • The southern black widow has the shiny, black, globular abdomen with the distinctive red hourglass on the underside.
    • The northern black widow has a row of red spots down the middle of the upper surface of its abdomen and two crosswise bars on the undersurface. The markings can also be yellow or white, and the spider itself may be brown or have red legs.
  • Black widow spiders are nocturnal and, thus, are active at night. They prefer dark corners or crevices. They are said to avoid human dwellings, but you can find them in such areas as outhouses and garages. Only the female black widow bites humans, and she bites only when disturbed, especially while protecting her eggs.
Picture of the underside of a black widow spider and an egg sack
Picture of the underside of a black widow spider and an egg sack
Picture of a top view of a black widow spider
Picture of a top view of a black widow spider

What are the symptoms of a black widow spider bite?

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.

Should I see a doctor if I get bitten by a black widow?

Treatment for serious reactions to a black widow spider's bite will be beyond the scope of most medical offices and urgent care centers. Pain relief may require the use of narcotics and antivenin (antitoxin to counteract the effects of the spider venom).

The decision to seek emergency care should be made early. If the person who was bitten by a black widow spider has more than minor pain or has whole-body symptoms, seek care at the nearest hospital's emergency department. If symptoms are severe, call 911 for emergency medical transport so that evaluation and treatment can start en route to the hospital.

Medically Reviewed by a Doctor on 10/14/2016

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Spider Envenomation, Widow »

Widow spiders belong to the genus Latrodectus and include the black widow spider (Latrodectus mactans mactans) in the United States.

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