Most spider bites heal on their own with basic first aid: clean the wound, apply a cool cloth, and keep the area elevated. The vast majority of spiders lack fangs strong enough to break human skin, and those that do typically cause nothing worse than a mild, itchy bump that fades within a few days. The exceptions are bites from black widows and brown recluses, which can cause serious symptoms and need medical attention.
Immediate First Aid Steps
Wash the bite with mild soap and water as soon as you notice it. Apply a cool cloth over the bite for 15 minutes each hour. You can use a clean cloth dampened with water or wrapped around ice. If the bite is on your hand, arm, foot, or leg, keep the limb elevated to reduce swelling.
Over-the-counter pain relievers like ibuprofen or acetaminophen can help with soreness. An antihistamine taken by mouth can ease itching. Avoid scratching the bite, which opens the skin to infection.
One important note: don’t clean the wound with hydrogen peroxide or rubbing alcohol. Both can slow healing. Stick with soap and water.
How to Tell if a Bite Is Serious
A typical spider bite looks like a small red bump, similar to a mosquito bite. It may itch or sting mildly for a day or two, then fade. If that’s all you’re dealing with, home care is enough.
Black widow bites cause painful swelling around the bite that can worsen over the first 12 hours before it begins to improve. The venom affects the nervous system, so symptoms often spread well beyond the bite itself. You may feel severe muscle cramps, especially in the abdomen and back, along with a racing pulse, headache, or nausea.
Brown recluse bites follow a different pattern. The bite site feels like it’s burning and changes color over the first few days, sometimes developing a bullseye appearance or a bluish bruise. Three to five days after the bite, a small ulcer may form. In severe cases, the skin around that ulcer breaks down between seven and 14 days, creating a wound that can take months to fully close. The good news: the majority of brown recluse bites heal within three weeks without reaching that severe stage.
When to Get Emergency Care
Call for medical help if you experience any of these after a bite:
- Difficulty breathing or tightness in the chest
- Severe muscle pain or cramping, especially if it spreads beyond the bite
- Heart palpitations or a racing pulse
- Nausea and vomiting
- Vision problems or a severe headache
- Signs of infection such as fever, increasing redness, or yellow discharge from the wound
Children under 16 and adults over 60 are more vulnerable to black widow venom and more likely to need hospital-level care for breathing problems, heart issues, or dangerous blood pressure spikes. If someone in these age groups is bitten, err on the side of seeking care quickly.
What Happens at the Hospital
For black widow bites with serious symptoms, doctors can administer antivenom, which neutralizes the spider’s toxin. It’s typically reserved for people with severe muscle pain, breathing trouble, or cardiovascular symptoms. Elderly patients in particular tend to benefit from receiving antivenom early. The treatment is derived from horse serum, so people with a known allergy to horse products may need alternative approaches.
For brown recluse bites, hospital treatment focuses on wound care. If the bite develops into a large ulcer, you may need regular wound dressings and follow-up visits to monitor healing. Antibiotics are prescribed if the wound becomes infected, but they aren’t given routinely for every bite.
It Might Not Be a Spider Bite
Many skin infections get mistakenly blamed on spiders. MRSA, a type of antibiotic-resistant staph infection, is one of the most common lookalikes. In its early stages, MRSA appears as a red, swollen bump that’s warm to the touch and painful, which sounds a lot like a spider bite. The difference becomes clearer over a day or two: a MRSA infection tends to develop a red ring of spreading redness (cellulitis), drain pus, or cause a fever.
A useful trick: draw a circle around the edges of the red area with a pen. Check it again 24 to 48 hours later. If the redness or swelling has expanded beyond your circle, that’s a sign of a spreading infection rather than a simple bite, and you should get it evaluated.
Tetanus and Spider Bites
Spider bites that break the skin are considered puncture wounds, which the CDC classifies as “dirty or major” when it comes to tetanus risk. If you’ve completed your primary tetanus vaccine series and your last booster was less than five years ago, you don’t need another shot. But if your last tetanus vaccination was five or more years ago, or if you’re unsure of your vaccination history, a booster is recommended after any puncture wound. This is especially relevant for bites that become necrotic or ulcerated, since damaged tissue creates an environment where the tetanus bacterium can thrive.
Healing Timeline for Most Bites
A bite from a common house spider or garden spider typically itches for a day or two and disappears within a week. You may see a small red mark at the site for a few days longer.
Brown recluse bites follow a more drawn-out timeline. If the spider injected only a small amount of venom, discomfort should fade within three to five days. Bites with more venom involvement can form an ulcer around day three to five, with the surrounding skin potentially breaking down between days seven and 14. Severe wounds may take several months to fully heal, though most people recover within three weeks. Black widow symptoms tend to peak around 12 hours after the bite and then gradually improve, with full recovery typically taking several days to a week depending on severity.
During healing, keep the bite clean by washing it gently with soap and water once or twice daily. Watch for signs of secondary infection: increasing redness, warmth, swelling, pus, or fever. These signal that bacteria have entered the wound and you need treatment.