Most spider bites heal on their own with basic first aid: clean the area, apply ice, and keep it elevated. The vast majority of spiders can’t break human skin or deliver medically significant venom, so a typical bite causes mild redness and swelling that resolves within a few days. The exceptions are bites from black widows and brown recluses, which need medical attention. Here’s what to do and what to watch for.
Immediate First Aid Steps
Wash the bite with mild soap and water as soon as you notice it. This is the single most important thing you can do to prevent infection. Apply a cold pack wrapped in a cloth for 10 to 15 minutes at a time to reduce swelling and numb the pain. If the bite is on an arm or leg, keep that limb elevated above the level of your heart when resting.
Over-the-counter pain relievers like ibuprofen or acetaminophen can help with soreness. If the area is itchy, an oral antihistamine or hydrocortisone cream can take the edge off. Avoid scratching the bite, which opens the skin to bacteria and slows healing.
What Not to Do
Venom suction kits do not work. Studies have shown these devices extract virtually no venom from a wound. One analysis found the fluid pulled out contained only 1/10,000th the concentration of actual venom. Worse, suction devices can collapse tissue near the surface and may push venom deeper, increasing local damage without reducing systemic effects. The Wilderness Medical Society and other medical organizations recommend against them. The same goes for older folk remedies like cutting the wound, applying tourniquets, or using heat. All of these are more likely to cause harm than help.
Signs That Need Emergency Care
Most spider bites are minor, but certain symptoms mean you should get to an emergency room:
- Severe or worsening pain, especially abdominal cramping
- Difficulty breathing or swallowing
- A growing wound at the bite site or spreading redness and red streaks
- You saw the spider and it looked like a black widow (shiny black with a red hourglass) or brown recluse (tan with a violin-shaped marking)
- You’re not sure whether the spider was dangerous
If the person bitten is a young child, an older adult, or someone with a compromised immune system, err on the side of getting medical attention sooner.
Black Widow Bites
A black widow bite feels like a sharp pinprick, followed by dull numbness at the site. The venom attacks nerve endings, and within an hour or two you may develop intense muscle pain, stiffness, and spasms that can spread to the abdomen, shoulders, chest, and back. Other symptoms include headache, nausea, excessive sweating, fever, chills, and difficulty breathing.
Hospital treatment typically involves muscle relaxants and pain medication to control the spasms. In severe cases, doctors may use antivenom delivered through an IV. Symptoms usually ease within about 30 minutes of receiving antivenom, though it carries a risk of serious allergic reaction and is reserved for life-threatening situations.
Brown Recluse Bites
Brown recluse bites progress in stages, which is part of what makes them tricky. In the first three to eight hours, the area becomes red, sensitive, and starts to burn. It may develop a bullseye pattern or turn bruise-blue. Over the next three to five days, if only a small amount of venom was injected, the discomfort fades. If the venom spread, an ulcer forms at the bite site.
In severe cases, the skin around the ulcer breaks down between seven and 14 days after the bite, creating a wound that can take months to fully heal. By three weeks, most bites have formed a thick black scab over the healing area. Left untreated, the wound can become infected or scar significantly. If you suspect a brown recluse bite, get medical evaluation early, before the tissue breakdown progresses.
It Might Not Be a Spider Bite
This is worth knowing: many skin lesions blamed on spiders turn out to be something else entirely. One of the most common lookalikes is a staph infection called MRSA, which causes painful, swollen, pus-filled bumps that people often assume are spider bites because of “how bad it looks.” Misdiagnosing MRSA as a spider bite delays the right treatment and can lead to serious complications.
A few clues point away from a spider bite. Spiders produce a single lesion per bite. If you have multiple sores at the same time, multiple sores appearing over several days, or other people in your household have similar lesions, a spider is almost certainly not the cause. That pattern is far more consistent with a bacterial skin infection. If you didn’t see the spider, consider seeing a healthcare provider who can evaluate whether the wound needs antibiotics rather than just bite care.
Normal Healing Timeline
A bite from a common, non-dangerous spider typically improves within a few days. You’ll see redness and minor swelling peak in the first 24 to 48 hours, then gradually fade. Some itching is normal as it heals. If the redness keeps expanding after 48 hours, or the center of the bite darkens or opens, that’s a sign something more significant is going on, whether from venom or infection, and warrants a medical visit.