Most spider bites are harmless and heal on their own with basic first aid. Wash the bite, ice it, and take an over-the-counter pain reliever. The vast majority of spiders lack venom strong enough to cause anything more than temporary redness, swelling, and mild pain similar to a bee sting. Only two spiders in the United States pose a real medical threat: the brown recluse and the black widow.
First Aid for a Spider Bite
For any spider bite, start with these steps as soon as you notice it:
- Clean the area with warm, soapy water to reduce infection risk.
- Apply a cold pack or cool washcloth for 10 to 15 minutes at a time to bring down swelling.
- Apply antibiotic ointment to the bite to help prevent infection.
- Take a pain reliever if needed. For adults, 400 to 600 milligrams of ibuprofen or 500 to 1,000 milligrams of acetaminophen works well.
- Use an antihistamine like diphenhydramine (Benadryl) if itching or hives develop.
If the bite is on your arm or leg, keep the limb elevated when you can. This helps fluid drain away from the area and reduces swelling. Most non-venomous bites improve noticeably within a few days and fully resolve within a week or two.
How to Tell if a Bite Is Serious
Most of the time, you won’t even see the spider that bit you. That makes it hard to know exactly what you’re dealing with. The key is watching how the bite evolves over the next several hours to days.
Brown Recluse Bites
Brown recluse bites are tricky because they often don’t hurt much at first. Pain, burning, and redness typically build over several hours or even days. The signature pattern is a bite wound that develops a pale or bluish center surrounded by a whitish ring and then a larger red outer ring, creating a bull’s-eye appearance. In more severe cases, the center of the wound darkens and forms an open ulcer as the surrounding skin dies. You may also develop fever, chills, body aches, nausea, or a rash.
Not every brown recluse bite leads to tissue destruction. Many heal without significant scarring. But when skin breakdown does occur, it can take weeks or months to fully close, and some wounds need medical attention to prevent infection or promote healing.
Black Widow Bites
Black widow bites feel different right away. You’ll notice immediate pain and burning at the site, sometimes with two small fang marks visible. Within an hour or two, the venom can cause intense muscle cramping that spreads from the bite into the abdomen, back, chest, and shoulders. The abdominal cramping can be severe enough to be mistaken for appendicitis.
Other symptoms include sweating, nausea, vomiting, tremors, dizziness, restlessness, and eyelid swelling. Weakness or partial paralysis in the legs can occur in more severe cases. These systemic symptoms are what make black widow bites a medical concern, even though the bite wound itself usually looks minor.
When You Need Emergency Care
Get medical help right away if any of these apply:
- You know or suspect you were bitten by a brown recluse or black widow.
- Severe pain develops, especially abdominal cramping or pain that worsens steadily over several hours.
- The wound is growing or developing a dark center with surrounding redness.
- Red streaks spread outward from the bite, which signals an infection moving through the tissue.
- Breathing or swallowing becomes difficult.
If you can safely capture or photograph the spider, bring it with you. Identification helps doctors decide on the right treatment approach.
What Happens at the Doctor’s Office
For brown recluse bites, treatment is mostly supportive. Doctors typically recommend rest, ice, compression, and elevation along with anti-inflammatory medication and antihistamines to manage swelling. If the bite develops into an open wound, you may need a tetanus booster and antibiotics to prevent secondary infection. Severe tissue breakdown sometimes requires wound care over several weeks, and rarely, surgical cleaning of dead tissue.
For black widow bites, the focus is on controlling pain and muscle spasms. Antivenom exists and is generally reserved for severe cases that don’t respond to other treatments. Children and older adults with other health conditions are typically prioritized for antivenom when symptoms are serious.
Rare but Serious Complications
In uncommon cases, brown recluse venom triggers a body-wide reaction rather than just a local wound. This can happen regardless of how bad the bite looks on the surface. Symptoms of this systemic reaction include a widespread rash, high fever, joint pain, and in the most severe cases, breakdown of red blood cells, kidney damage, or seizures. These complications are rare but require hospital-level care.
Black widow bites very rarely cause death in healthy adults, but the muscle cramping and pain can be debilitating for days. Young children, elderly adults, and people with heart conditions face a higher risk of serious complications.
Helping the Bite Heal at Home
Once you’ve done the initial first aid, keep the bite clean and watch it closely. Wash it daily with mild soap and water, and reapply antibiotic ointment. Avoid scratching, which can introduce bacteria and lead to infection. Continue icing the area for the first 24 to 48 hours if swelling persists.
Take a photo of the bite each day. This gives you a visual record of whether it’s improving or worsening, which is especially useful if you end up needing medical advice. A bite that’s getting smaller, less red, and less painful is on the right track. A bite that’s growing, darkening, or becoming more painful after the first day or two needs professional evaluation.
Most non-venomous spider bites resolve in one to two weeks. Even mild brown recluse bites without significant tissue involvement often heal within three to four weeks. Bites that develop open ulcers can take considerably longer, sometimes two to three months, and may leave a scar.