Spider Bites: How to Identify, Treat and When to Worry

Spider bites are widely feared and widely misunderstood. The reassuring reality is that the vast majority of spiders cannot meaningfully harm you, and many marks blamed on spiders are something else entirely. Here is a calm, practical guide.

Most "spider bites" are not bites

Doctors regularly find that lesions reported as spider bites are in fact bacterial infections, insect stings or skin conditions. True spider bites are uncommon because spiders bite to subdue prey, not people — they bite humans only when trapped against skin. If you did not see a spider do it, it most likely was not a spider.

What a harmless bite looks like

A typical bite from a common spider resembles other insect bites:

• A small red bump, sometimes with two faint puncture points
• Mild swelling, itching or tenderness around the spot
• Symptoms that fade over a few days

This kind of bite needs nothing more than basic care.

Simple first aid

1. Wash the area with soap and water.
2. Apply a cold compress to reduce swelling and pain.
3. Elevate the limb if it is a hand or foot.
4. Avoid scratching, which invites infection.
5. Take an over-the-counter antihistamine or pain reliever if needed.

The two species that warrant caution

In most of the world, only two groups are medically significant: widow spiders and recluse spiders.

• A widow bite may bring muscle cramps, sweating and abdominal pain within hours.
• A recluse bite is usually painless at first but can, in some cases, develop into a slow-healing wound.

When to see a doctor

Seek medical care promptly if you experience spreading or severe pain, muscle cramps, fever, nausea, difficulty breathing, or a wound that worsens over days — or if a child, an older adult or anyone with a known sensitivity is bitten.

If you can do so safely, photograph the spider for identification — it genuinely helps clinicians. But never delay medical care to catch a spider, and never handle one you suspect is dangerous. Identify from a distance, treat the symptoms, and when in doubt, get it checked.