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.

Black Widow Spider Bite

The black widow is a medium-sized spider — about a half-inch long. Two species are common to the United States:

• The southern black widow. This spider has a shiny, black, globe-shaped abdomen. You’ll know it by the red hourglass mark on the underside.
• The northern black widow. You’ll notice a row of red spots down the middle of the upper surface of its abdomen. It also has two crosswise bars on the underside. Just to make things interesting, the markings can also be yellow or white. The spider may be brown or have red legs.

These spiders are active at night. They prefer dark corners or crevices, like garages. They only bite when disturbed.

Symptoms

The black widow spider makes a venom that affects your nervous system. Some people are slightly affected by it, but others may have a severe response. Right away, you may feel severe pain, burning, swelling, and redness at the site. You may even see two fang marks.

Other symptoms include:

• Muscles that begin to hurt and become stiff, usually within 8 hours
• Nausea or vomiting
• Difficulty breathing
• Severe abdominal pain or cramping
• Excessive sweating
• Rash and itching
• Swollen eyelids
• Weakness or tremors. You may not be able to move your legs.

Many of the symptoms of a black widow bite can look like those of other conditions. But if you think you’ve been bitten by this spider, make an appointment to see your doctor.

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IMPORTANT: If you suspect your child was bitten by a black widow, get to the emergency room right away. These bites can be fatal in young children.

In the meantime, try these tips to ease your symptoms and prevent further infection:

• Wash the area with soap and water.
• Apply a cold washcloth or ice pack wrapped in cloth to the area.
• Take an over-the-counter pain reliever, like Tylenol.
• If the bite is on your arm or leg, elevate it to prevent swelling.
• Apply an antibiotic cream or lotion to the bite.

If possible, kill and capture the spider (place it in a plastic bag or jar) and take it to your doctor appointment. This way, they’ll know for sure that it was a black widow that bit you.

Your doctor will review your symptoms and decide what more treatment, if any, is needed. If they’re severe, you may need muscle relaxants or stronger pain medicine. You may have to stay in the hospital, though that’s rarely the case.

In the most severe cases, your doctor may inject you with antivenin. It’s a drug made from substances in the blood of horses. Antivenin neutralizes the black widow’s venom. That means it prevents it from causing you harm.

Your doctor will only use this treatment after they’ve spoken with another doctor who has experience in treating these bites. Antivenin can cause a number of side effects, so if your doctor gives it to you, they’ll have to monitor you for about 8 to 12 days afterward.

Prevention

Black widow spiders live in cool, dark places like sheds and garages. They normally bite when they’re startled or surprised. To reduce your risk of being bitten, keep storage areas clean. And outside, try to avoid woodpiles, fallen tree branches, and other places they may hide.

Show Sources

Mayo Clinic: “Spider Bites: First Aid.”

KidsHealth.org: “First Aid: Spider Bites.”

Munson Healthcare Cadillac Hospital: “Spider Bites.”

Johns Hopkins Medicine: “Spider Bites.”

Stanford Children’s Health: “Spider Bites in Children.”

Merck & Co.: “Antivenin.”

Black Widow Spider Bite

Medically reviewed by Drugs.com. Last updated on Jan 5, 2023.

What do I need to know about a black widow spider bite?

The venom from a black widow spider is poisonous. Symptoms of a reaction to the venom start about 30 minutes after the bite. Symptoms are usually mild and stop within a few days, but severe symptoms that last several days are possible. Venom can spread from the bite to other parts of your body. It can damage your muscles, nerves, or organs.

What are the signs and symptoms of a black widow spider bite?

• A sharp pain like a pinprick, or pain that spreads from the bite area to other areas
• Red, numb, tingling, stinging, or burning skin at the bite area
• Muscle cramps or spasms
• Nausea or vomiting
• A cold sweat

How is a black widow spider bite treated?

Treatment depends on how severe your symptoms are. You may need any of the following:

• NSAIDs , such as ibuprofen, help decrease swelling, pain, and fever. This medicine is available with or without a doctor’s order. NSAIDs can cause stomach bleeding or kidney problems in certain people. If you take blood thinner medicine, always ask if NSAIDs are safe for you. Always read the medicine label and follow directions. Do not give these medicines to children younger than 6 months without direction from a healthcare provider.
• Prescription pain medicine may be given. Ask your healthcare provider how to take this medicine safely.
• Muscle relaxers may be given to relieve cramps or spasms.
• A tetanus vaccine is a booster shot used to help prevent tetanus. Tetanus is a severe infection that can develop in the bite wound.
• IV fluids may be needed to prevent dehydration and kidney failure.
• Antivenom may be given if your symptoms are severe or you are at increased risk. Antivenom can help slow or stop your symptoms.

How do I manage my symptoms?

• Elevate your wound above the level of your heart as often as you can. This will help decrease swelling and pain. Prop a bitten arm or leg on pillows or blankets to keep it elevated comfortably.
• Apply ice to your wound for 15 to 20 minutes every hour or as directed. Use an ice pack, or put crushed ice in a plastic bag. Cover it with a towel before you apply it to your wound. Ice helps prevent tissue damage and decreases swelling and pain.
• Care for your wound as directed. Carefully wash the wound with soap and water. Dry the area and watch for signs of infection, such as fever, redness, and swelling.

When should I contact my healthcare provider?

• You have increased pain or a change in how your pain feels.
• You have a fever or a headache.
• Your wound is red, swollen, or draining fluid.
• Your eyes become sensitive to light.
• You have pain when you move the bitten body part, or the part is difficult to move.
• You get tender lumps in your groin or armpits.
• Your symptoms spread from the bite to other parts of your body.
• You have questions or concerns about your condition or care.

When should I seek immediate care or call 911?

• You have severe abdominal pain.
• Your wound turns blue or black and smells foul.
• Your muscles become stiff and start to cramp or spasm.
• You have tremors or trouble breathing, talking, or walking.
• Your heart is racing.
• You have chest pain, tightness, or heaviness that may spread to your shoulders, arms, jaw, neck, or back.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

© Copyright Merative 2022 Information is for End User’s use only and may not be sold, redistributed or otherwise used for commercial purposes.

Learn more about Black Widow Spider Bite

Care guides

• Brown Recluse Spider Bite
• Snake Bite

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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.

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 a 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.

  What Are the Symptoms of a Black Widow Spider Bite?

  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.

  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.

  QUESTION

  Should I See a Doctor If I Get Bitten by a Black Widow?

  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.

  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.

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  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.

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