Most spider bites are harmless and share the same symptoms as a bee sting, including pain, redness, and swelling. All spiders make venom but most of them have fangs that are too small to puncture the skin. This is why most bites do not cause serious symptoms.2
Venomous spiders in the United States include the brown recluse and black widow. They normally only bite if they feel trapped or have been touched.
The brown recluse spider is known as the violin spider because of the violin-shaped mark on its back. It is about 1 inch long. While most spiders have eight eyes, the brown recluse has six.
Brown recluse spiders are commonly found in the Midwest and the South in the United States. They usually live in dry, secluded areas like underneath log piles or in rocks and leaves. Indoors, they may be found in dark areas of the house like closets or the attic.
A brown recluse spider will only bite when it meets with pressure from a human. For example, if you place your foot in your shoe, not knowing a spider was inside, you would be bitten. Brown recluse spider bites may sting at first, then feel painful. You may notice a small white blister at the site of the bite.
Symptoms usually last for 24–36 hours and include:
- Joint pain
The brown recluse bite can cause the skin to deteriorate, known as skin necrosis, and needs medical treatment right away.5
Black widow spiders are black, with a red hourglass pattern on their underside. Black widow spiders are mostly found in the U.S. South and the West but can live anywhere in North America.
They prefer to live in undisturbed areas and may be found under woodpiles. They can also live near outdoor toilets because of the abundance of flies, which they will eat.
Black widow spiders tend to build their webs between objects. These spiders usually bite when a human comes into contact with one of their webs.
A black widow spider bite has two puncture marks. Because this spider’s venom is a neurotoxin (poison that impacts the nervous system), the pain will start at the site of the bite and then spread to other areas of the body.6
Other symptoms may last for several days and include:
- Muscle tension or stiffness
- Profuse sweating (perspiration)
- Trouble breathing
- Increased blood pressure