Finding a red, itchy bump and suspecting a spider can be unsettling, especially if you’ve heard stories about dangerous species. The reality is that the vast majority of spider bites are harmless and heal on their own within a week, much like a mosquito or bee sting. A small number of species can cause serious reactions, though, so it’s worth knowing how to treat a spider bite properly and which symptoms mean you need medical help.
Is It Really a Spider Bite?
Doctors point out that many skin lesions blamed on spiders are actually something else: insect bites, a skin infection, or an allergic reaction. Spiders rarely bite people, and when they do it’s usually because they’ve been trapped against the skin, for example in clothing, shoes, or bedding. If you didn’t see a spider, keep an open mind. A painful, swollen, pus-filled spot that keeps growing may be a bacterial infection or a boil rather than a bite.
Common Symptoms of a Harmless Spider Bite
- A small red bump, sometimes with two tiny puncture marks.
- Mild pain, similar to a bee sting.
- Itching and mild swelling around the bite.
- Redness that fades over a few days.
How to Treat a Spider Bite: First Aid
Step 1: Move Away and Stay Calm
Move away from where the bite happened to avoid another bite. If you can do so safely, take a photo of the spider or capture it in a jar; this can help a doctor identify it if symptoms develop.
Step 2: Wash the Bite
Clean the area with mild soap and water. This removes any bacteria on the skin and lowers the risk of infection.
Step 3: Apply a Cold Compress
Wrap ice or a cold pack in a cloth and hold it on the bite for 10 to 15 minutes at a time. Cold reduces swelling, pain, and the spread of venom. Don’t put ice directly on the skin.
Step 4: Elevate the Area
If the bite is on an arm or leg, raise it above heart level to help reduce swelling.
Step 5: Relieve Pain and Itching
Over-the-counter pain relievers such as ibuprofen or acetaminophen help with discomfort. For itching, an oral antihistamine or hydrocortisone cream can help. Calamine lotion also soothes itchy bites.
Step 6: Watch It Closely
Keep an eye on the bite for the next 24 to 48 hours. Draw a pen line around any redness so you can tell whether it’s spreading.
What Not to Do
- Don’t try to suck out venom or cut the bite.
- Don’t apply a tourniquet.
- Don’t scratch, as broken skin can become infected.
- Don’t apply heat, which may increase swelling.
Dangerous Spiders to Know About
Black Widow
Black widows are shiny black with a red hourglass marking on the underside. Their bite may feel like a pinprick at first, but within an hour it can cause muscle cramps, severe abdominal or back pain, sweating, nausea, and a racing heart. These symptoms need emergency care. Antivenom is available for severe cases.
Brown Recluse
Brown recluse spiders are light brown with a darker violin-shaped mark on their back. Found mainly in the central and southern United States, they hide in dark, undisturbed places like closets and attics. A bite may be painless at first, then become red and painful, sometimes forming a blister and a sinking, darkening sore that can damage skin tissue over days. Seek medical care promptly.
Funnel-Web and Redback (Australia)
In Australia, funnel-web spider bites are a medical emergency and require immediate first aid with a pressure bandage and an ambulance. Redback bites (relatives of the black widow) cause intense pain and sweating and also need medical assessment.
When to Seek Medical Help
Get medical attention right away if you notice:
- Severe pain, cramping, or muscle spasms.
- Difficulty breathing or swallowing, or swelling of the face, lips, or throat (signs of an allergic reaction).
- Sweating, nausea, vomiting, headache, or fever.
- A wound that becomes larger, darker, or forms an open sore.
- Redness spreading out from the bite, warmth, or pus, which suggest infection.
- A suspected bite from a black widow, brown recluse, or funnel-web spider.
Young children, older adults, and people with heart conditions are at higher risk of serious reactions and should be seen sooner rather than later.
Spider Bites on Children and Pets
Children are more vulnerable to venom because of their smaller body size, so take any suspected bite from a black widow, brown recluse, or funnel-web seriously and get medical advice quickly. For mild bites, the same first aid applies: wash, cool, and watch. Keep children’s nails short and distract them from scratching, which can lead to infection. Ask a pharmacist about child-safe doses of antihistamines and pain relievers.
Dogs and cats can also be bitten, usually on the face or paws. Signs of a serious bite in pets include swelling, limping, drooling, vomiting, muscle tremors, or weakness. Contact your vet if you suspect a venomous spider bite.
Spider Bite vs. Other Bites
It can be difficult to tell spider bites apart from other bites. Mosquito bites are usually small, puffy, and very itchy, and they often appear in clusters on exposed skin. Flea and bedbug bites tend to appear in lines or groups. Tick bites may have the tick still attached; if so, follow the steps for removing a tick safely. A single painful bump with two small puncture marks, especially one that appeared after putting on stored clothing or reaching into a dark space, is more likely to be a spider bite.
How Long Does a Spider Bite Take to Heal?
A typical harmless bite fades within three to seven days. Bites that blister or become infected take longer. Necrotic brown recluse wounds can take weeks to heal and may need specialist wound care.
How to Prevent Spider Bites
- Shake out shoes, gloves, and clothing that have been stored in garages or sheds.
- Wear gloves when moving firewood, boxes, or garden debris.
- Keep beds away from walls and don’t let bedding touch the floor.
- Reduce clutter in closets, basements, and attics.
- When camping, keep tents zipped and check sleeping bags before getting in. Many of the same habits help with preventing mosquito bites while hiking.
Frequently Asked Questions
How do I know if a spider bite is serious?
Warning signs include severe pain, muscle cramps, sweating, nausea, trouble breathing, or a wound that darkens and grows. Seek medical help if any of these appear.
What does a spider bite look like?
Most spider bites look like a small red, swollen bump, sometimes with two tiny puncture marks. Many look identical to other insect bites.
Should I put ice or heat on a spider bite?
Use a cold compress. Ice reduces swelling and pain. Avoid heat, which can increase inflammation.
Can a spider bite get infected?
Yes. Scratching can break the skin and let bacteria in. Keep the bite clean and watch for spreading redness, warmth, or pus.
How long do spider bite symptoms last?
Mild bites usually improve within a few days and heal within a week. Bites from dangerous species can cause symptoms that last longer and need medical treatment.