Health Library

Spiders are arachnids (as are ticks, mites, and scorpions), not insects. Spiders rarely bite people. When they do, it’s usually in self-defense because they’re being crushed by a human. 

Usually, their venom (like a poison) is not strong enough to hurt humans. So spider bites usually go unnoticed, or they may look like any other bug bite.

A few types of spiders can cause problems for people when they bite. In the US, the spiders to watch out for are:

• Brown recluse spiders. This small oval brown spider has long skinny legs with a body that’s about half an inch (10 mm) long. It has a dark violin shape on top of its head. They’re found mostly in midwestern and southern parts of the United States. They hide in dark, quiet places like attics or garages, under porches, and in woodpiles. 
  Signs of a bite: A brown recluse spider bite usually won’t hurt at first, so a person might not know they were bitten. But some bites cause swelling, changes in skin color, and a blister, which later can become a large open sore. Rarely, other general symptoms like chills, fever, nausea, and body aches can follow a brown recluse bite.
• Black widow spiders. This small shiny black spider with long skinny legs is about half an inch (10 mm) long, with an orange-red or yellow hourglass shape on its underbelly. They’re found all over the world, and live in damp, dark places like woodpiles, tree stumps, trash piles, storage sheds, fruit and vegetable gardens, stone walls, and under rocks. 
  Signs of a bite: A black widow spider bite might not hurt or can feel like a little pinprick. An hour or two later, the bite area can hurt and swell, and painful cramps may spread to the rest of the body, especially the arms, legs, back, and stomach. A bite also can lead to weakness, shakiness, nausea, vomiting, sweating, and headache.
• Tarantulas. This large hairy spider isn’t nearly as dangerous as it looks. They’re found all over the world and can grow up to 5 inches (13 cm) long. Those in the United States are usually about half that size. Tarantulas live in nests in the ground and avoid people whenever they can. 
  Signs of a bite: A tarantula’s bite will be red, swollen, and painful like a bee sting. Its venom is very weak, so bites usually don’t cause more serious reactions in other parts of the body. Tarantulas also can release hairs from their body if they feel threatened. These can irritate the skin or eyes,  and cause pain, redness, itchiness, or swelling that can last for weeks.

Handling Spider Bites

Here’s how to handle a spider bite:

• Wash the bite area carefully with soap and water.
• Apply cool compresses or an ice pack to the bite.
• Keep the bite area raised and still to prevent the venom from spreading.
• Give acetaminophen or ibuprofen for pain.
• To protect against infection, apply an antibiotic ointment and keep your child’s hands washed.
• Try to catch the spider that bit your child, so that it can be identified. You can kill it first — just be sure not to squish it so much that no one can tell what type it is.

If you think your child might have a brown recluse or black widow spider bite:

• Go to the emergency room. Even with no symptoms, your child should get medical attention right away.

Doctors treat spider bites with medicines to ease symptoms. For example, people with black widow spider bites might need medicines that reduce pain and relax the muscles. Doctors might give antivenom to people with underlying medical problems or who don’t get better from the other medicines. A brown recluse spider bite might be treated with antibiotics if the bite gets infected. If the skin around the bite gets very damaged, a person might need surgery.

How Can We Prevent Spider Bites?

The best way to prevent a spider bite is to be careful in areas like undisturbed piles of rocks or wood, seldom-opened boxes, or corners behind furniture. Anyone who works in an area with piles of logs or leaves should wear gloves.

Shake out blankets and clothing that have been stored in the attic or the basement, or those that are in a closet but haven’t been used in a long time.

Check behind furniture before cleaning or playing there. If you keep shoes in a garage, basement, or mudroom, shake them out before wearing them.

And if you spot a tarantula, leave it alone. They will not bite unless they feel threatened.