How Do You Know if You Have Been Bitten By a Spider?

Most spider bites cause redness, swelling, and pain. More dangerous spiders such as the brown recluse spider and black widow spider cause additional symptoms and require medical attention.

Most spider bites are harmless, cause minor symptoms, and go away on their own. In North America, there are two types of poisonous spiders whose bites may cause more serious symptoms—the brown recluse spider and the black widow spider.

The brown recluse—also called the violin spider—is about an inch and a half long and has a violin-shaped marking on its head. No deaths from a brown recluse spider have occurred in North America. 

The black widow spider is all black with a red hourglass on its back. It is also shiny.

A bite from either of these types of spiders requires emergency medical treatment.

Most bites from spiders cause:

• Redness
• Swelling
• Pain

However, brown recluse spider bites also cause:

• White and red bullseye around the bite
• A blue or purple center of bite
• Black blister
• Nausea
• Vomiting
• Headache
• Rash
• Fever
• Joint pain
• Stiff joints
• Aches
• Fatigue

Black widow spider bites can cause:

• Strong muscle cramps that show up within 8 hours of the bite
• A hard-to-find bite
• Stomach pain
• Stiff belly
• Nausea
• Vomiting
• Difficulty breathing

Some people have allergic reactions to spider bites. Signs of an allergic reaction to a spider bite include:

• Swollen face
• Swollen mouth
• Difficulty swallowing
• Trouble talking
• Difficulty breathing
• Wheezing
• Tight feeling in the chest

Spider bites are caused by venomous spiders. There are more than 50 spiders in the U.S. that bite but are not harmful.

If you suspect the spider that bit you or someone else was a brown recluse or a black widow, seek medical attention right away.

Otherwise, see the doctor for a spider bite if you have:

• Signs of an allergic reaction
• Pain with cramping
• Signs of infection including: 
  • Pus
  • Warm to the touch
  • More redness
  • Worsening swelling
  • Increasing pain

To diagnose brown recluse and black widow spider bites, it is most helpful if you saw the spider. However, that is not always possible.

Doctors usually diagnose spider bites based on examining the bite and reviewing your symptoms. In some cases, a spider expert may help with the diagnosis.

Prevention

Prevention for spider bites includes cleaning cobwebs out of the places spiders enjoy like:

• Garages
• Attics
• Woodpiles
• Closets

Wear long sleeves and long pants when in these locations to reduce the risk of a spider bite. Keep firewood outside the house to keep spiders out. Shake out items that have been in storage before using them. Make noise before going into places where spiders like to live to scare them away before you get there.

At-home treatment

You can treat most spider bites at home. First, wash the bite with soap and water to prevent infection. Use an icepack to help with pain or swelling.

If the pain is especially bad, take over-the-counter pain medication. You can also take an antihistamine like Benadryl to reduce swelling.

Brown recluse spider bites

Treatment for brown recluse bites includes managing symptoms. Doctors may give antihistamines for extreme swelling. They may also prescribe antibiotics to avoid infection. Some brown recluse bites require surgery if the bite is especially deep. If you get a brown recluse bite, you'll also receive a tetanus booster.

Black widow spider bites

There is an antivenom for serious black widow bites, but doctors only use it if you have trouble breathing. Otherwise, they treat muscle cramps with muscle relaxers and treat the intense pain with prescription pain medication.