What is spider bites?

Insect bites and stings and spider bites: Overview

Insect and spider bites often cause minor swelling, redness, pain, and itching. These mild reactions are common. They may last from a few hours to a few days. Home treatment is often all that's needed to relieve the symptoms of a mild reaction to common stinging or biting spiders and insects, such as fleas, flies, and mosquitoes.

Some people have more severe reactions to bites or stings. Babies and children may be more affected than adults are.

Examples of problems that are more serious include:

  • A severe allergic reaction (anaphylaxis). These reactions aren't common. But they can be life-threatening and require emergency care. They may cause:
    • Shock. This can occur if the circulatory system can't get enough blood to the vital organs.
    • Coughing, wheezing, trouble breathing, or a feeling of fullness in the mouth or throat.
    • Swelling of the lips, tongue, ears, eyelids, palms of the hands, soles of the feet, and mucous membranes (angioedema).
    • Lightheadedness and confusion.
    • Belly pain, nausea, vomiting, or diarrhea.
    • Raised, red, itchy bumps called hives and red skin. These symptoms often occur with other symptoms of a severe reaction.
  • A toxic reaction to a single sting or bite. Spiders or insects that may cause this include:
    • Black widow spiders.
    • Brown recluse spiders.
    • Scorpions.
    • Puss caterpillars (woolly slugs).
  • A toxic reaction to multiple stings or bites from a bee, wasp, or fire ant.
    • A bee leaves its stinger behind and then dies after stinging. Africanized honeybees, the so-called killer bees, are more aggressive than common honeybees. They often attack together in great numbers. Reaction to bee stings can range from minor skin swelling and redness to a serious allergic reaction.
    • Wasps, including hornets and yellow jackets, can sting over and over.
    • A fire ant is a wingless insect. It attaches to a person by biting with its jaws. Then, pivoting its head, it stings from its belly in a circular pattern at multiple sites.
  • A large skin reaction with swelling and redness that spreads away from the site of the bite or sting. It may be as large as swelling across two major joints, such as from the elbow to the shoulder.
  • A skin infection at the site of the bite or sting.
  • Serum sickness. This is a reaction to the medicines (antiserum) used to treat a bite or sting. It may cause hives and flu-like symptoms, such as a fever, muscle aches, or a headache about 3 to 21 days after the use of antiserum.
  • A virus infection. Infected mosquitoes can spread the West Nile virus to people, causing an inflammation of the brain (encephalitis).
  • A parasite infection. Infected mosquitoes can spread malaria.

What are the symptoms of a toxic reaction to spider venom?

Bites from spiders usually cause pain, swelling, redness, and itching at the site of the bite. In some people, especially children, the redness and swelling may be worse and last up to a few days.

A few people have severe reactions to the toxin injected by spiders. A toxic reaction occurs when the spider venom acts like a poison in the body. This type of reaction can occur from one bite from a highly toxic spider, or from multiple bites from spiders not normally considered poisonous.

Symptoms of a toxic reaction vary depending on the spider, the toxicity of the venom, and the amount of venom injected. Most often, symptoms improve or go away within 48 hours. Although hives and difficulty breathing may occur in an allergic reaction, these symptoms will not occur in a toxic reaction. It is possible to have both a toxic reaction and an allergic reaction at the same time.

A toxic reaction may require immediate medical care or may lead to death. Signs and symptoms of a toxic reaction may include:

  • Nausea or vomiting.
  • Diarrhea.
  • Fever.
  • Weakness.
  • Lightheadedness.
  • Rapid swelling at the site of the bite or sting.
  • Muscle spasms.
  • Headache.
  • Drowsiness.
  • Fainting.

Hobo spider

Female Hobo spider

The Hobo spider, a light brown spider with a yellowish-green tint on its abdomen, ranges in size from 0.4 in. (1 cm) to 0.6 in. (1.5 cm) . Hobo, or Northwestern brown, spiders (Tegenaria agrestis) are common and widespread in Europe and western central Asia. Since their introduction to North America in the early 1900s, hobo spiders have spread to British Columbia, Alaska, Oregon, Idaho, Montana, and Utah. These spiders build funnel webs in wood, rock, or debris piles.

Preventing spider bites

Follow these tips to avoid bites from spiders.

  • Brush a spider off of you.

    If a spider gets on you, brush it off. Do not crush it.

  • Protect your hands.

    Wear gloves if working in an area where spiders are likely to live.

  • Avoid spider habitats.

    Look for spiders in low-lying webs in garages, in barbecue grills, around swimming pools, and in wood piles.

    Avoid wood or rock piles and dark areas where spiders live.

  • Clear out junk.

    Clear away old furniture, tires, junk, newspaper, and old clothes. This will eliminate places spiders like to live.

  • Plug openings and crevices into the house.
  • Protect your bed.

    Move your bed away from walls so spiders will be less likely to creep into bed with you.

    Shake out and check bedding for spiders before getting in the bed.

  • Check your clothing.

    Shake out and check clothing and shoes for spiders before putting them on.

  • Do not leave your child's toys outside.
  • Use insecticides.

    Consider spraying insecticides on any high-risk areas, such as known black widow spiderwebs, indoor cracks and crevices, closets, attics, wood piles, and under eaves and around baseboards and window areas. Repeat treatment is usually necessary.

How can you care for a spider bite or scorpion sting?

  • Put ice or a cold pack on the area for 10 to 20 minutes at a time. Put a thin cloth between the ice and your skin.
  • Try an over-the-counter medicine for itching, redness, swelling, and pain. Be safe with medicines. Read and follow all instructions on the label.
    • Take an over-the-counter antihistamine to help calm the itching or swelling.
    • Put a hydrocortisone 1% cream or calamine lotion on the skin.
  • Don't scratch or rub the skin around the area.

What are common stinging or biting insects and spiders?

Insects that cause mild reactions include:

  • Bedbugs.
  • Kissing bugs.
  • Chiggers.
  • Fleas.
  • Flies.
  • Mites.
  • Mosquitoes.
  • Nonpoisonous spiders.
  • Ticks.
  • Scabies.
  • Lice.

Some insects are more likely than others to cause allergic or toxic reactions.

  • A bee leaves its stinger behind and then dies after stinging. Africanized honeybees, the so-called killer bees, are more aggressive than common honeybees and often attack together in great numbers. Reaction to bee stings can range from minor skin swelling and redness to a serious allergic reaction.
  • Wasps, including hornets and yellow jackets, can sting over and over. Yellow jackets cause the greatest number of allergic reactions.
  • A fire ant attaches to a person by biting with its jaws. Then, pivoting its head, it stings from its abdomen in a circular pattern at multiple sites.

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The content above contains general health information provided by Healthwise, Incorporated, and reviewed by its medical experts. This content should not replace the advice of your healthcare provider. Not all treatments or services described are offered as services by us. For recommended treatments, please consult your healthcare provider.