Spider Bite Treatment: What to Do

Spider bites are far less common than most people believe — the vast majority of skin reactions attributed to spider bites are actually caused by other insects, bacterial infections, or skin conditions. True spider bites typically occur when a spider is accidentally disturbed or trapped against skin. For most Missouri homeowners, the realistic concern is limited to two species: the brown recluse and the black widow.

Here is how to respond if you suspect a spider bite.

First Aid for Any Suspected Spider Bite

• Remain calm — the vast majority of spider bites are minor
• Clean the bite site thoroughly with soap and water
• Apply a cold pack or ice wrapped in cloth to reduce swelling and pain — do not apply ice directly to skin
• Elevate the bitten limb if possible
• If you can do so safely, capture the spider in a sealed container for identification — this is valuable information for medical professionals
• Note the time the bite occurred and any immediate symptoms

When to Seek Medical Care Immediately

Go to an emergency room or urgent care promptly if any of the following occur:

• Difficulty breathing, swallowing, or rapid swelling of the face or throat — signs of a severe allergic reaction
• Severe muscle cramping, especially in the abdomen or back — a sign of black widow envenomation
• The bite victim is a young child, elderly, or has a compromised immune system
• You are confident the bite was from a black widow or brown recluse
• Symptoms are worsening rather than improving over several hours

Recognizing a Brown Recluse Bite

Brown recluse bites are often not felt at the moment of the bite, or feel like a mild sting. Symptoms develop over hours to days:

• Hours 0–8: Mild stinging or burning at the bite site; may develop a small red or white blister
• Hours 8–24: The bite may develop a "bull's-eye" appearance — a central pale area surrounded by a reddened ring, sometimes with a darker outer ring
• Days 2–5: In necrotic cases, the central tissue begins to die and a dark scab (eschar) develops; the wound may continue to expand slowly
• Weeks following: Necrotic wounds are slow to heal, sometimes taking months

Not all brown recluse bites become necrotic — many cause only mild local reaction that resolves within a week. A physician evaluation is important to monitor the wound and provide appropriate treatment.

Recognizing a Black Widow Bite

Black widow bites are more immediately symptomatic than brown recluse bites:

• The bite itself may cause immediate sharp pain or may be felt as only a pinprick
• Within 30 to 60 minutes, muscle pain and cramping typically begins, often felt in the abdomen, back, and chest
• Other symptoms can include sweating, nausea, elevated blood pressure and heart rate, and a general feeling of severe illness
• Symptoms typically peak within several hours and can last 1 to 3 days

Seek medical care promptly for any suspected black widow bite, especially in children. Antivenom is available and effective for severe envenomations.

Most Suspected Spider Bites Are Not Spider Bites

Studies have consistently shown that the majority of lesions presented to doctors as "spider bites" are actually caused by other insects, staph infections (MRSA in particular can produce necrotic skin lesions similar to brown recluse bites), Lyme disease, or other conditions. If you did not actually see a spider bite you, consider other possibilities before attributing a skin lesion to a spider bite.

A physician evaluation is always appropriate for any unexplained, worsening skin lesion — regardless of the suspected cause.