Most spider bites are harmless and heal on their own with basic first aid: clean the wound, ice it, and watch for changes. The vast majority of spiders lack venom strong enough to cause serious harm to humans. But knowing the right steps to take immediately, what to watch for over the following days, and which symptoms signal a real emergency can make a significant difference in how well and how quickly a bite heals.
Immediate First Aid Steps
Start by washing the bite area with mild soap and water. Apply antibiotic ointment three times a day to help prevent infection. Then place a cool, damp cloth or a cloth filled with ice over the bite for 15 minutes each hour to reduce pain and swelling. If the bite is on an arm or leg, elevate that limb when you can.
For pain, an over-the-counter pain reliever works well. If the bite is itchy, an antihistamine like diphenhydramine (Benadryl) or cetirizine (Zyrtec) can help. These simple measures are all most spider bites will ever need.
How to Tell It’s Actually a Spider Bite
Here’s something most people don’t realize: many “spider bites” aren’t spider bites at all. A staph skin infection, including MRSA, can look almost identical to a spider bite, with a red, swollen, painful bump that may blister or drain pus. Unless you actually saw the spider on your skin, it’s worth considering that the wound could be a bacterial infection instead, which requires completely different treatment. If a red, tender bump appears with no clear bite history, getting it checked is a smart move.
True spider bites usually show two tiny puncture marks, though these can be hard to spot. The surrounding area typically swells, reddens, and may itch or sting. Most bites from common house spiders look like a mild bee sting and resolve within a few days.
Brown Recluse Bites: A Slow Progression
Brown recluse bites are tricky because they often go unnoticed at first. The initial sensation is minimal, sometimes just a light sting. But over 6 to 8 hours, the pain intensifies as blood flow to the tissue around the bite decreases. The area may turn blue or dark red by the end of the first day.
The timeline of changes is distinctive. Within the first hour, the bite area may swell to about the size of a quarter. By 24 to 72 hours, a clear or blood-filled blister typically develops at the site, which later forms a dark scab of dead tissue. The majority of brown recluse bites heal within three weeks if the reaction stays mild. In severe cases, the skin around the wound breaks down into an ulcer that can take several months to heal completely, sometimes requiring skin grafting after four to six weeks of treatment.
Not every brown recluse bite causes this necrotic reaction. Many produce only minor redness and heal without complications. But the slow onset means you should keep a close eye on any bite you suspect came from a recluse, even if it looks fine at first.
Black Widow Bites: Body-Wide Symptoms
Black widow bites produce a very different pattern. Instead of local skin damage, the venom affects your nervous system, triggering symptoms throughout the body. A moderate reaction includes sweating and cramping pain in the large muscles of your trunk, with normal heart rate and blood pressure.
A severe reaction, sometimes called latrodectism, ramps up significantly. You may experience intense, widespread muscle cramping in your abdomen, shoulders, chest, and back. The abdominal pain can be so severe it mimics a surgical emergency. Other symptoms include headache, nausea, vomiting, high blood pressure, rapid heart rate, difficulty breathing, restlessness, anxiety, and a diffuse red rash.
For severe reactions, hospitals can administer antivenom. It’s most effective when given early but can still work up to 36 hours after the bite. Death from black widow bites is rare, but without treatment, symptoms can linger for weeks or even months.
When to Go to the Emergency Room
Get medical care right away if any of these apply:
- You were bitten by a spider you recognize as a black widow or brown recluse
- You’re not sure whether the spider was dangerous
- You have severe pain or abdominal cramping
- The wound is growing or getting worse
- You’re having trouble breathing or swallowing
- Red streaks are spreading outward from the bite
Spreading redness or red streaks are particularly important to act on quickly, as these can indicate a developing infection moving through your system.
Tetanus and Infection Risk
Spider bites that cause tissue death, like severe brown recluse bites, fall into the category of wounds that carry increased tetanus risk. According to CDC guidelines, if you’ve completed your tetanus vaccine series but your last booster was five or more years ago, a dirty or necrotic wound warrants a new shot. If your vaccination history is unknown or incomplete, any wound type calls for vaccination.
For a simple, clean spider bite that isn’t breaking down, tetanus isn’t a major concern as long as you’re up to date on your shots (within the last 10 years for minor wounds).
What Not to Do
Resist the urge to cut the bite open, try to squeeze out venom, or apply a tourniquet. These old-school approaches don’t help and can introduce infection or damage tissue further. Don’t apply heat to the bite during the first few days, as warmth increases blood flow and can worsen swelling. Stick with cool compresses instead.
Avoid scratching the bite, even when it itches intensely. Broken skin from scratching is one of the easiest paths to a secondary bacterial infection, which can complicate healing significantly. Use antihistamines and cold compresses to manage the itch.
What Healing Looks Like
A typical minor spider bite follows a predictable path: redness and swelling peak within the first day or two, then gradually fade over a week. Itching often outlasts the visible swelling by a few days. The whole process usually wraps up within one to two weeks.
Brown recluse bites with necrotic reactions take longer. Expect around three weeks for non-severe bites. If a deep ulcer forms, healing stretches to several months, and you’ll likely need ongoing wound care from a healthcare provider. During this period, keeping the wound clean and protected is essential to prevent secondary infection.
For black widow bites treated with antivenom, the body-wide symptoms typically resolve faster than without treatment, but muscle aches and fatigue can linger. Without antivenom, full recovery from a severe bite can take weeks to months.