Spider Bites 101: Symptoms, Treatment & When to Get Help
Medically Reviewed by Carolin Schneider, MD
Spider bites may seem scary — but the good news is that most spiders are harmless to people. In rare cases, poisonous spider bites can cause severe pain and other more serious symptoms. You can take care of most spider bites at home, but it’s important to get medical help if you have symptoms of a poisonous spider bite or an allergic reaction.
Harmless Spider Bites
Most spider bites are no cause for concern. They usually look like small red spots — similar to other common bug bites. They can also appear as slightly raised bumps and may feel itchy.
If you have mild pain or swelling, you can try an over-the-counter pain medicine or antihistamine (allergy medicine). Or try these steps to treat spider bites:
- Wash the bite area with soap and water.
- Use a cold wrap to reduce swelling.
- Put over-the-counter anti-itch cream on the bite.
Changes To Watch For
Even if a spider bite seems harmless at first, it’s important to keep an eye on the bite area and watch for any changes — especially if a child gets bitten. Ask your doctor for advice if you notice any of these changes:
- The bite gets worse within 24 hours.
- The red area grows larger than one inch across.
- Your pain keeps getting worse even after you take pain medicine.
These symptoms can be gradual and hard to notice, so keep watching the bite for any signs that it’s getting worse. If you think the spider may have been poisonous, tell your doctor right away.
Dangerous Spider Bites
In the United States, there are two poisonous spiders to watch out for: black widow spiders and brown recluse spiders.
- Black widow spiders are completely black, except for a red hourglass shape on the stomach. Symptoms of a black widow spider bite include pain that spreads to other parts of the body, abdominal cramps, fever, sweating, nausea and trouble breathing.
- Brown recluse spiders have a violin-shaped pattern around the neck and a hairless, brown body. Pain from a brown recluse spider bite increases in the eight hours after the bite. The bite may turn into an ulcer (sore) that turns black or blue and gets bigger as the skin around it dies. You may also feel very tired or have joint pain or fever.
If you think either of these spiders may have bitten you, get medical help right away.
Some people are allergic to spider bites. Symptoms of an allergic reaction include:
- Hives (itchy, red welts on the skin)
- Fast but weak pulse
- Trouble swallowing
- Trouble breathing
- Swelling in the face
A severe allergic reaction can be life-threatening, so get help right away if you have any of these symptoms.
How to Prevent Spider Bites
Spiders bite when they feel trapped or threatened, so the best way to prevent bites is to avoid places that are popular with spiders. When you’re outside, try not to disturb rocks or fallen trees and logs. Keep your garage, storage sheds and other outdoor spaces around your home clean and tidy. Black widows and brown recluses like warm, dark places, so be careful in indoor spaces like attics and cupboards as well.