Most spider bites are harmless and heal on their own within a few days. You should go in for medical care if you notice spreading redness, increasing pain, signs of infection, or any body-wide symptoms like muscle cramping, difficulty breathing, or chest tightness. If you know or suspect the spider was a black widow or brown recluse, seek care right away regardless of how the bite looks.
Signs You Can Treat It at Home
The vast majority of spider bites cause mild, localized symptoms: a small red bump, minor swelling, and some itching or soreness. If that describes your bite, home care is usually enough. Clean the area with mild soap and water, apply antibiotic ointment, and hold a cool cloth over the bite for about 15 minutes each hour to bring down swelling. Keeping the area elevated also helps. An over-the-counter antihistamine can ease itching, and calamine lotion or a hydrocortisone cream works well for irritation.
Monitor the bite for the next 24 to 48 hours. If it stays small, the redness doesn’t spread, and you feel fine otherwise, you’re likely in the clear.
When to Go to Urgent Care or the ER
Certain symptoms mean you should stop watching and start heading to a doctor. Here’s what to look for:
- Severe or spreading pain. Pain that radiates outward from the bite, especially into your abdomen, chest, shoulders, or back, is a hallmark of black widow venom. This can start within minutes of the bite.
- Muscle cramping or rigidity. Painful muscle spasms, particularly in the stomach and legs, signal that venom is affecting your nervous system.
- Difficulty breathing or swallowing. This could indicate either a venom reaction or anaphylaxis, both of which are emergencies.
- A growing wound or color change. A bite that develops a bullseye pattern, turns blue or purple, or blisters within 3 to 8 hours may be from a brown recluse. The tissue damage worsens over time without treatment.
- Red streaks spreading from the bite. Streaks of redness radiating outward suggest the infection is moving into your lymphatic system.
- Fever, pus, or yellow discharge. These are signs of secondary bacterial infection, which can develop days after the initial bite even if the spider itself wasn’t dangerous.
- Weakness, tremors, or paralysis. Any loss of strength or coordination, especially in your legs, warrants immediate emergency care.
If you’re unsure whether the spider was dangerous, err on the side of getting checked. There is currently no blood test or diagnostic kit that can confirm spider venom in your body. Doctors diagnose bites based on your symptoms and the bite’s appearance, so getting seen early gives them more information to work with.
Black Widow Bites Move Fast
Black widow venom is a neurotoxin, meaning it targets your nervous system. Symptoms don’t wait around. In a study of 59 patients, all of them developed severe pain at the bite site within minutes, with the pain spreading rapidly along blood vessels to the abdomen and limbs. Restlessness, anxiety, and difficulty breathing followed quickly.
The bite itself may look like a small pinprick with mild redness, so the appearance alone can be misleading. The giveaway is what happens to your body over the next 30 to 60 minutes: escalating pain, abdominal cramping that can feel like appendicitis, and tightness in the chest. If you experience any of this, call 911 or get to an ER.
Treatment typically involves pain management and medications to control muscle spasms. Antivenom exists for black widow bites and is highly effective at relieving symptoms and reducing hospital stays. Most experts recommend it for patients whose pain isn’t controlled by standard pain medication.
Brown Recluse Bites Develop Slowly
Brown recluse venom works differently. Instead of attacking the nervous system, it destroys skin and tissue around the bite. The tricky part is that you might not feel much at first. The real changes show up 3 to 8 hours later, when the bite site starts burning, turns red, and begins changing color. A classic pattern is a bullseye appearance or a bluish bruise-like discoloration. Blistering often follows.
Because tissue destruction worsens over time, getting medical attention within the first 24 hours gives you the best chance of limiting damage. Don’t wait for a wound to become obviously necrotic. If you see a bite turning darker, expanding, or blistering, that’s your signal to go in.
Watch for Allergic Reactions
Some people have an allergic response to spider venom that goes beyond the bite itself. Anaphylaxis can develop within minutes and includes hives or flushed skin across your body, swelling of the tongue or throat, wheezing, a rapid weak pulse, nausea, vomiting, dizziness, or fainting. This is a life-threatening emergency.
If you carry an epinephrine autoinjector, use it immediately. Even if symptoms improve after the injection, you still need to go to an emergency room because symptoms can return. If you don’t have an autoinjector, call 911. Anaphylaxis can be fatal without prompt treatment.
Children Need a Lower Threshold
Kids, especially infants and toddlers, deserve a quicker trip to the doctor. They have smaller body mass, which means venom concentrations hit harder and faster. An infant can’t tell you about spreading pain or muscle cramps. Inconsolable crying after a suspected bite is reason enough to seek evaluation. For any child where over-the-counter pain relief isn’t controlling the discomfort, get them seen.
Infection Can Show Up Days Later
Even if the initial bite seemed minor, keep watching the area for up to a week. Secondary bacterial infections are a common complication of any spider bite, venomous or not. The break in the skin lets bacteria in, and scratching makes it worse.
The warning signs are straightforward: increasing redness or warmth around the bite after the first day or two, pus or yellowish discharge, fever, or red streaks spreading outward from the wound. These symptoms mean bacteria have taken hold and you likely need antibiotics. Many skin infections that people assume are spider bites are actually bacterial infections like MRSA from the start, which is another reason spreading redness or warmth warrants a medical visit regardless of what caused the original wound.