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.

Black Widow Spider Bite Home Remedies

The options for home care are limited. Both cold and warm compresses have been recommended, as have hot baths. Obviously, over-the-counter pain relievers such as acetaminophen and ibuprofen may be of value in mild cases. Folk remedies have not proven to work.

What Is the Treatment for a Black Widow Spider Bite?

In general, extensive medical evaluation is not necessary. The exceptions are when the history of a black widow bite is not clear, if the bite was not witnessed, and when associated symptoms require the exclusion of more serious disorders, such as heart attack.

Black Widow Spider Bite Medications?

The person bitten by a black widow spider, who has pain severe enough to seek treatment at an Emergency Department, will require narcotic pain relief. Muscle relaxants given by injection may also be of value. Although calcium gluconate given through an IV has long been advocated, it does not seem to produce much relief of symptoms.

Use of antivenin

The antivenin available for treatment of black widow spider bites is derived from horse serum. The venom produced by various species of black widow spiders is similar, so the antivenin prepared against one venom is effective against the others. Antivenin is produced by gradually increasing injections of the specific venom in a horse. The horse then starts producing the antivenin, which will be used in humans.

Symptoms are often not easily relieved, even with narcotics. Some experts recommend that antivenin be used in any severe bite because one vial of the antitoxin produces significant and rapid relief of symptoms. It can even be used if there is delay in reaching the hospital. Yet other sources recommend that antivenin be used only in children, the elderly, and those with severe underlying medical conditions.

Horse serum-based antivenin carries a significant risk of a severe allergic reaction (anaphylaxis) which can be life-threatening. Skin testing before the serum is administered is therefore recommended. Although another side effect known as serum sickness (characterized by skin lesions, fever, pain in the joints, and swollen lymph glands) is common when horse serum is used to treat rattlesnake bites, it is uncommon when used to treat black widow spider bites (probably because of the low dose needed for relief).

Be aware, however, that this antivenin may not be readily available at most hospitals; there may be some delay or difficulty in obtaining it when needed.

Note: The use of the black widow antivenin might sensitize the person against later use of rattlesnake antivenin. Obviously, the physician should discuss lifestyle habits that might affect the person's risk of incurring a snakebite in the future. In many areas, black widow bites are much more common than rattlesnake bites.

What Is the Follow Up for a Black Widow Spider Bite?

Follow-up is always necessary in cases where antivenin is used. Although serum sickness is uncommon with single-vial doses of horse serum, it may occur 7-12 days after exposure and is characterized by skin lesions, fever, pain in the joints, and swollen lymph glands. The symptoms may occur sooner in a sensitized person. The process is self-limited, goes away in 2-3 weeks, and may be treated with antihistamines and steroids.

How Do I Prevent Spider Bites from Black Widows?

Because black widow spiders bite if they are disturbed, care should be taken in reaching into dark areas. In areas where spider infestations are a problem, the use of a pest control service may also be useful.

What Are the Complications from Black Widow Spider Bites?

Complications in healthy adults are uncommon. If the black widow spider bite is not treated with antivenin, symptoms may last for several days but are seldom life threatening.

Reviewed on 8/30/2017

Medically reviewed by Avrom Simon, MD; Board Certified Preventative Medicine with Subspecialty in Occupational Medicine

REFERENCE:

"Clinical manifestations and diagnosis of widow spider bites"
UpToDate.com

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