- Seek emergency care for trouble breathing, dizziness, confusion, or severe muscle stiffness after a spider bite.
- Intense pain, cramping, fever, nausea, vomiting, or blistering can be signs of a poisonous spider bite.
- Open sores, worsening swelling, or pain that spreads beyond the bite area need prompt medical evaluation.
Spider bites usually appear as a small skin wound with redness, swelling, pain, or itching. In many cases, spider bites are mild and caused by non-poisonous spiders, so symptoms may only be noticed hours later.
Although most spider bites are harmless, some can lead to more serious symptoms like intense pain, cramping, nausea, fever, or breathing problems. Bites from spiders like the black widow or brown recluse may require medical treatment due to their venom.
Many spider bites can be treated at home with basic first aid, such as gently cleaning the area and applying a cold compress, while more serious bites may require hospital care. Recognizing symptoms, knowing which spiders are dangerous, and following prevention steps can help lower your risk and ensure you get the right treatment.
Main symptoms
Common symptoms of a spider bite include:
- Mild swelling of the skin
- Redness around the bite
- A small wound at the site of the bite
- Pain or itching in the area
If possible, it is helpful to identify the type of spider that caused the bite, especially if a poisonous spider is suspected. Taking a picture of the spider and showing it to a healthcare provider can help guide treatment and may lead to faster care.
Symptoms of a poisonous spider bite
Symptoms of a poisonous spider bite are usually more severe than those of a common spider bite. They may include blisters, sweating, difficulty breathing, fever, intense pain, muscle cramping, abdominal stiffness, nausea, or vomiting.
How to identify a poisonous spider
According to the CDC, venomous spiders found in the United States include the black widow and the brown recluse, and most bites happen when a spider is trapped or touched. You can read more about them below:
1. Brown recluse
The brown recluse spider is often called the violin spider because of the distinctive violin-shaped marking on its head. It also has 6 eyes, which is unusual, since most spiders have 4 or 8. In the United States, brown recluse spiders are most commonly found in the Midwest and the southern regions.
Where they’re found: The brown recluse often lives in dark, dry places, such as woodsheds, inside walls, and crawl spaces.
Symptoms of a bite: This spider usually only bites when it is accidentally crushed against the skin, such as when it gets trapped in clothing or bedding. The bite causes an immediate stinging sensation and pain when the venom is injected, followed by a blister at the bite site. The venom can destroy nearby skin cells and lead to a serious wound due to tissue death (necrosis).
Special treatment: Bites that do not lead to open sores can usually be managed with cold compresses and pain relievers. However, bites that cause open sores and are not treated early may need more intensive care to remove dead tissue, and larger wounds may even require skin graft surgery.
2. Black widow
These spiders live throughout the United States but are most commonly seen in the southern and western regions. They have a shiny black body with a red marking on the underside.
Where they’re found: They typically live outdoors in dark, undisturbed places, such as woodpiles, under eaves, and beneath patios.
Symptoms of a bite: The bite usually leaves two small puncture marks where the spider injects a neurotoxic venom. This venom causes pain at the bite site that can spread to other areas, such as the chest and abdomen.
Special treatment: Treatment is usually provided in the hospital, where a local anesthetic can be injected around the bite to relieve pain. The pain typically improves within about 3 hours. Intravenous fluids are only needed if the person develops a slow heart rate or has trouble breathing.
How to prevent
To help prevent spider bites, it is important to keep your home clean and your yard free of clutter. Spiders tend to live and reproduce in dark, dirty, or humid areas. Piles of debris or stacked wood can attract spiders, so people who work near these areas are more likely to be bitten. In general, avoid keeping debris piles in or around your home.
If you live in or are traveling through areas where spiders are known to be common, you should shake out your clothing and shoes before putting them on.
First aid for a spider bite
To treat a spider bite, you should:
- Wash the bite area with soap and water.
- Elevate the affected limb, if possible.
- Avoid tightening or tying anything around the bite.
- Do not try to suck out or remove the venom.
- Apply a cold compress or a clean cloth dampened with cool or warm water to help relieve pain and swelling.
According to the American Red Cross, emergency care is recommended if severe symptoms develop, such as trouble breathing, muscle rigidity, dizziness, or confusion.