Spider Bites – Symptoms and Causes

Overview

Spider bites rarely cause serious harm. Most spiders can’t pierce human skin with their fangs, and only a few have venom strong enough to cause serious problems. When bites do occur, they typically happen when spiders feel threatened.

Common symptoms of spider bites include:

• Redness
• Pain
• Swelling

However, these symptoms appear with many other skin irritations, making spider bites difficult to identify unless you actually see the spider bite.

Of the thousands of spider species, only a small number pose risks to humans:

Spider Type	Estimated Number of Species
Widow spiders	Approximately 30 species
Recluse spiders	More than 140 species

Signs of Spider Bites

Black Widow Spider Bites

Most spider bites look like typical bug bites—red, swollen spots that might itch or hurt a little. However, black widow spider bites can cause more serious symptoms:

• Pain and swelling around the bite that may spread to your stomach, back, or chest.
• Severe cramping in the abdomen that might feel similar to appendicitis.
• Other symptoms include nausea, vomiting, tremors, and sweating.

These uncomfortable symptoms typically last between 1 and 3 days. If you notice these signs after a spider bite, seek medical help right away.

Brown Recluse Spider Bites

Brown recluse spider bites develop differently from other spider bites. Watch for these warning signs:

• Pain that worsens during the first 8 hours
• Fever, chills, and body aches
• A distinctive bite wound with:
  • Pale center
  • Dark blue or purple coloration
  • Red ring around the edge
• The bite may develop into an open sore where surrounding skin tissue dies

Many skin bumps can look like spider bites, but have other causes.

When to Get Emergency Medical Help

Get emergency medical care right away if:

• You were bitten by a dangerous spider, like a black widow or a recluse spider
• You’re not sure if the spider that bit you was dangerous
• You have severe pain, stomach cramps, or a growing wound where you were bitten
• You have trouble breathing or swallowing
• The bite area has spreading redness or red streaks

These symptoms may indicate a serious reaction that needs immediate treatment. Don’t wait to see if symptoms improve on their own.

Why Spider Bites Can Be Harmful

Spider venom can induce intense symptoms following a bite. How bad these symptoms get depends on three key factors:

1. Spider type – Different spiders have different types of venom.
2. Venom amount – More venom typically means worse symptoms.
3. Individual sensitivity – People react differently to the same venom.

Risk Factors

Understanding where dangerous spiders live can help you avoid bites. Certain spiders prefer specific environments, and knowing these can keep you safer.

Where Widow Spiders Live

Widow spiders thrive across most of the United States (except Alaska) and parts of Europe. They are especially common in rural Southern areas.

These spiders become more active during warm weather and typically make their homes in:

• Sheds and garages
• Unused garden equipment
• Stacks of firewood
• Indoor closets and cabinets during colder months

Widow spiders seek dark, undisturbed areas where they can build webs without being disturbed.

Where Recluse Spiders Live

Recluse spiders primarily inhabit the southern United States and South America. True to their name, these spiders prefer quiet, undisturbed locations.

They are most active when temperatures rise. Inside homes, recluse spiders often hide:

• In cluttered basement corners and attics
• Behind furniture, like bookshelves
• In seldom-opened cupboards

Many bites happen in the early morning because these spiders sometimes crawl into bedding or clothing.

Outdoors, recluse spiders make their homes in dry, dark places such as under rocks or inside hollow tree stumps.

Complications

Widow spider or recluse spider bites can sometimes cause serious problems. In rare cases, these bites can be fatal, especially for young children.

A bad bite from a recluse spider may take several weeks or even months to heal completely. These bites often leave significant scarring on the skin after they heal.

Prevention

Spiders only bite when they feel threatened. They’re usually trapped between something and your skin. Here are ways to reduce your risk of spider bites:

Identify and Avoid Dangerous Spiders

• Learn to recognize harmful species
• Also, find out where they typically live
• Understand their preferred environments so you can be more cautious in those areas

Wear Protective Clothing

• Long-sleeved shirts and pants
• Hats to protect your head
• Tuck pants into socks
• Gloves when handling stored items or firewood
• Boots when cleaning storage areas like attics, basements, and sheds

Practice Good Habits

• Shake out clothing and footwear before putting them on
• Apply insect repellents, like DEET, according to package instructions
• Flick spiders off your skin rather than crushing them against yourself
• Use gloves, masks, and eye protection when cleaning spider enclosures

Spider-Proof Your Home

• Install tight-fitting screens on windows and doors
• Seal cracks and openings where spiders can enter
• Use safe indoor insecticides
• Remove webs and spiders when found inside
• Keep beds away from walls, with only their legs touching the floor
• Avoid storing items under beds or letting bedding touch the floor

Manage Your Yard:

• Remove rock or lumber piles near your house
• Don’t store firewood against your home’s exterior walls