Spider Bite

Is this your symptom?

  • Spider bite
  • Or, there are bite symptoms (redness, pain, swelling) and a spider was seen nearby

Some Basics...

  • There are over 20,000 species of spiders in the world. Most of these spiders cause harmless bites in humans.
  • In the United States, there are two species that cause serious bites in humans. These are the black widow (Lactrodectus) and the brown recluse (Loxosceles).
  • If you see your doctor, bring the spider along in a jar for identification. Brown recluse spiders are very hard to identify.
  • Sometimes people wrongly believe that they have had a spider bite. Instead, they may have a skin infection with bacteria called Staphylococcus aureus (MRSA).

Black Widow Spider Bite

  • Description: A shiny, jet-black spider with long legs. The total size of the spider is 1 inch (25 mm). It may have a red or orange hourglass-shaped marking on its underside. This will not be on all spiders of this species.
  • Habitat: Found throughout North America. They are not found in Alaska or the far North.
  • Symptoms - Bite Wound: The bite causes moderate to severe pain right away. There is most often little to no reaction at the bite.
  • Symptoms - Systemic: Severe muscle cramps within 1- 6 hours. These will last 24-48 hours. Other symptoms include stomach pain, vomiting, restlessness, hypertension, and weakness.
  • Treatment - Wound Care: Wash bite with soap and water. Put an ice pack on the bite.
  • Treatment - Medications: Tetanus prophylaxis should be provided. Parenteral analgesics may be needed for pain and benzodiazepines for muscle spasms. There is a Lactrodectus anti-venom that is used for severe symptoms, seizures, or very high blood pressure.
  • What to Expect: Symptoms most often go away in 2-3 days. These bites rarely cause death. A bite is more serious in a small child, as are multiple bites.
  • Special Note: Many bite wounds are "dry bites." This means that no poison was injected into skin.

Brown Recluse Spider Bite

  • Also known as the "violin" or "fiddleback" spider.
  • Description: A brown spider with long legs. The total size of the spider is ½ inch (12 mm). It has a dark violin-shaped marking on top of its head. This will not be on all spiders of this species.
  • Habitat: Found in the Southern, Southwestern and Midwestern United States.
  • Symptoms - Bite Wound: The spider's poison causes cell destruction and blood cell breakdown. The bite is first painless or minimally painful. There will be pain and blisters at the bite within 4-8 hours. The middle becomes bluish and crater-like over 2-3 days. The skin inside the crater may die. This is called a necrotic ulcer.
  • Symptoms - Systemic: These include fever, vomiting, and muscle aches. There are no life-threatening symptoms.
  • Treatment - Wound Care: Wash bite with soap and water. Put a cold pack on the bite.
  • Treatment - Medications: Tetanus prophylaxis should be provided.
  • What to Expect: Most necrotic ulcers heal over 1-8 weeks. Scarring happens to 10-15% of bites. Skin damage sometimes needs skin grafting.

Tarantulas

  • Habitat: Tarantulas are found in the Southern United States (like the Desert Southwest).
  • Symptoms - Bite Wound: Mild stinging with a little swelling at the bite. The bite does not cause skin tissue to die.
  • Symptoms - Eye: Some tarantulas have hairs that can come off. Like a fiberglass fragment, they can penetrate skin and cause itching and redness. If they lodge in the eye, they can cause eye problems.
  • Symptoms - Systemic: None.
  • Treatment - Wound Care: Clean the bite wound with soap and water. Put a cold pack on it and take pain medicine. Get a tetanus booster if it has been more than 10 years since last shot.
  • Treatment - Eye Irritation: See an eye doctor if you have irritation or redness after handling a tarantula. The doctor will perform a slit lamp exam of the eye.
  • What to Expect: Bite wounds fully heal. Eye problems often go away under the care of an eye doctor.

Minor (Non-Dangerous) Spider Bites

  • More than 50 spiders in the United States and Canada have poison. They can cause minor, non-serious reactions. Single, unexplained painful bites that happen during the night can be from spiders.
  • Symptoms - Bite Wound: The bites are painful and mildly swollen for 1-2 days. They may look like a bee sting.
  • Symptoms - Systemic: None.
  • Treatment - Wound Care: Clean the bite wound with soap and water. Put a cold pack on the bite and take pain medicine. Get a tetanus booster if it has been more than 10 years since last shot.
  • What to Expect: Bite wounds fully heal.

When to Call for Spider Bite

Call 911 Now

  • Trouble breathing or swallowing
  • Very weak (can't stand)
  • You think you have a life-threatening emergency

Call Doctor Now or Go to ER

  • Bite has redness, red streak, or is very tender to touch, and have a fever
  • You feel weak or very sick
  • You think you need to be seen, and the problem is urgent

Call Doctor Within 24 Hours

  • Bite area is red or very tender to touch and this started over 24 hours after the bite
  • Bite area is red or very tender to touch and it is getting larger over 48 hours after the bite
  • Diabetes and a spider bite on your foot
  • Bite starts to have a blister, ulcer, or turn purple
  • Eye is irritated after handling or touching a tarantula
  • You think you need to be seen, but the problem is not urgent

Call Doctor During Office Hours

  • You have other questions or concerns

Self Care at Home

  • Non-serious spider bite

Care Advice

Treatment of Non-Serious Spider Bites

  1. What You Should Know:
    • There are over 20,000 species of spiders in the world. Most of these spiders cause harmless bites in humans.
    • You can treat non-serious spider bites at home.
    • Here is some care advice that should help.
  2. Cleansing: Wash the bite with soap and water.
  3. Pain Medicine:
    • You can take one of the following drugs if you have pain: acetaminophen (Tylenol), ibuprofen (Advil, Motrin), or naproxen (Aleve).
    • They are over-the-counter (OTC) pain drugs. You can buy them at the drugstore.
    • Use the lowest amount of a drug that makes your pain feel better.
    • Acetaminophen is safer than ibuprofen or naproxen in people over 65 years old.
    • Read the instructions and warnings on the package insert for all medicines you take.
  4. What to Expect: You will have some swelling and pain for 1-2 days. It should not be any worse than a bee sting.
  5. Call Your Doctor If:
    • Severe bite pain lasts more than 2 hours after pain medicine
    • Stomach pains or muscle spasms
    • Bite pain lasts more than 2 days (48 hours)
    • Bite begins to look infected (redness, red streak, or is tender to touch)
    • You think you need to be seen
    • You get worse

Preventing Spider Bites

  1. Prevention - Outdoors:
    • Be careful near wood piles and when clearing brush.
    • Wear long pants with the pants tucked into your socks.
    • Wear long-sleeved shirts and use gloves.
    • DEET is a very strong insect repellent. It also repels spiders.
  2. Prevention - Indoors:
    • Remove spider webs.
    • Make certain that doorways and windows are sealed and insulated.
  3. Using DEET-Containing Insect Repellents When Outdoors:
    • DEET is a very strong insect repellent. It also repels spiders.
    • Higher strength DEET works better. All DEET over 50% works the same. For children and teens, the American Academy of Pediatrics recommends a maximum strength of 30%. Health Canada recommends using a strength of 5-30% for adults.
    • Spray on exposed areas of skin. Do not put near your eyes, mouth or any irritated skin. Do not put it on skin that is covered by clothing.
    • Always wash it off with soap and water when you return indoors.
    • DEET can damage clothing made of synthetic fibers, plastics, and leather.
    • Women who are breastfeeding may use DEET. No problems have been found.
    • Read all label instructions.

And remember, contact your doctor if you develop any of the 'Call Your Doctor' symptoms.

Disclaimer: This information is not intended to be a substitute for professional medical advice. It is provided for educational purposes only. You assume full responsibility for how you choose to use this information.


Last Reviewed: 10/20/2017 1:26:02 AM
Last Updated: 5/7/2017 1:36:18 PM

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Black Widow Spider

This is a photo of the Black Widow spider (Lactrodectus)

  • The black widow is shiny and black, with long legs (total width 1 inch).
  • A red (or orange) hourglass-shaped marking may be on its underside. However, this marking is not present in all Lactrodectus species.
Brown Recluse Spider

This is a photo of the Brown Recluse Spider (Loxosceles reclusa).

  • It is a brown spider with long legs (total width 1/2 inch).
  • There is a characteristic violin-shaped marking is visible on back.

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