Most spider bites are harmless and heal on their own within about a week. The immediate steps are simple: clean the bite, ice it, and watch for warning signs. Only two spiders in the United States, the black widow and the brown recluse, cause bites that can become medically serious. Here’s exactly what to do, starting from the moment you notice a bite.
Immediate First Aid Steps
Wash the bite area with mild soap and water. This is the single most important thing you can do right away, because it reduces the risk of infection. Then apply a cool, damp cloth or a cloth-wrapped ice pack to the bite for 15 minutes each hour. This helps with both pain and swelling. If the bite is on an arm or leg, keep that limb elevated when you can.
Over-the-counter pain relievers like ibuprofen can help manage soreness, and an antihistamine can reduce itching if the area is bothering you. Avoid scratching the bite, which can break the skin and invite bacteria in. Don’t apply a tourniquet, try to suck out venom, or cut the bite open. None of that helps.
Try to Identify the Spider
If you can safely capture or photograph the spider, do it. A clear photo on your phone is often enough for a doctor to determine whether the bite is from a medically significant species. If the spider is dead, place it in a sealed container or zip-lock bag. Don’t tape it down, since tape makes identification nearly impossible even under a microscope. If you didn’t see the spider, don’t panic. Most bites can be managed based on symptoms alone.
What a Black Widow Bite Looks Like
Black widow venom is a neurotoxin, meaning it interferes with the chemical signals in your nerve endings. The bite itself might feel like a pinprick and leave two small puncture marks. Within an hour or two, though, you can develop severe pain, muscle stiffness, and cramping that spreads well beyond the bite. The cramping commonly hits the abdomen, shoulders, chest, and back, and can feel intense enough that people sometimes mistake it for a medical emergency like appendicitis.
Other symptoms include restlessness, sweating, headache, nausea, and elevated blood pressure. Children under 16 and adults over 60 are at the highest risk for serious complications and often need hospital care. With prompt treatment, most people recover fully within 24 to 48 hours. Antivenom exists for black widow bites and is typically reserved for young children, older adults, and severe cases. For otherwise healthy adults, doctors often manage symptoms with pain medication and muscle relaxants instead.
What a Brown Recluse Bite Looks Like
Brown recluse bites follow a slower, more visual progression. In the first three to eight hours, the bite area becomes red, sensitive, and feels like it’s burning. The skin may develop a bullseye pattern or take on a bruised, bluish color.
By three to five days, if the venom has spread beyond the initial bite, an ulcer can form at the site. In severe cases, over the next one to two weeks, the skin around the ulcer breaks down into an open wound. The majority of brown recluse bites heal within three weeks, with a thick black scab covering the wound as it closes. But severe wounds can take several months to fully heal and sometimes leave a scar. There is no commercially available antivenom for brown recluse bites in the U.S., so treatment focuses on wound care and preventing infection.
Warning Signs That Need Medical Attention
Get medical help if you experience any of these after a spider bite:
- Spreading redness or swelling that grows significantly over hours
- Severe muscle pain or cramping beyond the bite area
- Fever, chills, nausea, or vomiting
- Difficulty breathing
- A wound that opens or develops pus, which suggests infection
- A rash that spreads across your body
Systemic reactions, where the venom affects your whole body rather than just the bite area, are responsible for nearly all serious outcomes from spider bites. Seizures, a sudden drop in blood pressure, and generalized rash are rare but require emergency care.
One practical trick: if the area around the bite looks red and swollen but you’re unsure whether it’s getting worse, draw a circle around the edge of the redness with a pen. Check again in a few hours. If the redness has expanded beyond your circle, that’s a clear signal to see a doctor.
It Might Not Be a Spider Bite
Many skin infections get misidentified as spider bites, and MRSA (a type of antibiotic-resistant staph infection) is one of the most common culprits. Early MRSA looks almost identical to a minor bite: a red, swollen bump that’s warm and painful to the touch. The key difference is that MRSA tends to worsen steadily, producing more swelling, drainage, and sometimes fever, while a typical spider bite improves within a few days.
If you didn’t actually see a spider bite you, keep infection on your radar. The pen-circle method works here too. Expanding redness, increasing warmth, pus, or fever all point toward a bacterial infection rather than a spider bite, and you’ll need antibiotics rather than just waiting it out.
Healing Timeline for Typical Bites
A bite from a common house spider or garden spider generally heals within a week without any special treatment beyond basic first aid. You might have a small red bump, some itching, and mild soreness for a few days.
Brown recluse bites take longer. Expect sensitivity and color changes in the first week, possible ulceration by the end of the first week, and full healing at around three weeks for most cases. Severe necrotic wounds are the exception and can stretch recovery to several months. Keep any healing bite clean and dry, and watch for signs of secondary infection like increased redness, warmth, swelling, or discharge.
If your last tetanus shot was more than five years ago and the bite has broken the skin in a way that looks dirty or deep, a booster is worth discussing with your doctor. For clean, minor wounds, the threshold is 10 years since your last shot.