Are Brown Widow Spiders Poisonous?
Brown widow spiders (Latrodectus geometricus) are indeed venomous, but their venom is generally considered less potent and dangerous compared to their close relatives, the black widow spiders (Latrodectus mactans and Latrodectus hesperus). Brown widow spiders are found primarily in tropical and subtropical regions, and their range has been expanding in recent years.
The venom of brown widow spiders contains neurotoxins, similar to black widows, which can cause various symptoms in humans when bitten. However, the severity of the symptoms tends to be milder with brown widow bites. Common symptoms of a brown widow spider bite may include localized pain, redness, swelling, and, in some cases, mild muscle cramps and nausea. Severe reactions are rare, and fatalities from brown widow bites are exceedingly rare.
Not all brown widow spider bites result in envenomation, and even when envenomation occurs, the effects are usually not life-threatening. If bitten by a brown widow spider or any spider that you suspect may be venomous, it's advisable to seek medical attention, especially if you experience severe allergic reactions.
Brown Widow Spider Venom
Brown widow spider venom is potent and neurotoxic, similar in composition to that of the more infamous black widow, but significantly less dangerous to humans. It contains a powerful neurotoxin called latrotoxin, which targets the nervous system by triggering an excessive release of neurotransmitters such as acetylcholine and norepinephrine. This causes overstimulation of muscles and nerves, leading to the symptoms collectively known as latrodectism.
The venom potency per drop of a brown widow (Latrodectus geometricus) is actually higher than that of a black widow, but the quantity injected in a typical bite is much smaller. Additionally, brown widows are less aggressive and tend to bite only when directly threatened—usually when someone presses against them or disturbs their egg sac.
Typical symptoms of a brown widow bite include:
Localized pain, redness, and swelling at the bite site
Mild muscle cramps or spasms near the affected area
Occasional nausea, headache, or malaise
Rarely, more systemic symptoms like muscle rigidity or chest pain (usually milder than black widow envenomation)
Severe reactions are uncommon, and fatalities are extremely rare. Most cases resolve with basic wound care, ice, and over-the-counter pain relief. Only occasionally is medical treatment, such as muscle relaxants or antivenom, necessary—mainly for young children, the elderly, or those with allergic sensitivities.
Brown Widow Spider Envenomation
If you are bitten (envenomated) by a brown widow spider (Latrodectus geometricus), it’s important to respond calmly but promptly. Although brown widow bites are rarely serious, proper care can prevent complications and ease symptoms. Here’s what to do:
Move to Safety
Immediately step away from the area where the spider is located to avoid additional bites. Brown widows are shy and generally only bite when trapped or threatened, but it’s best to ensure you’re no longer near the spider.
Clean the Bite Site
Wash the area thoroughly with soap and warm water to remove any surface contaminants and reduce infection risk.
Gently pat dry with a clean towel.
Apply a Cold Compress
Use a cold pack or clean cloth filled with ice for 10–15 minutes at a time to minimize pain and swelling.
Do not apply ice directly to the skin—wrap it in a thin cloth.
Alternate 10 minutes on and 10 minutes off for up to an hour.
Manage Pain and Swelling
Take an over-the-counter pain reliever such as ibuprofen (Advil) or acetaminophen (Tylenol) as needed.
Antihistamines like diphenhydramine (Benadryl) can help reduce itching or mild allergic swelling.
Avoid scratching the bite site to prevent secondary infection.
Stay Hydrated and Rest
Drink plenty of fluids and rest to help your body recover. Most mild symptoms resolve within a few hours to a couple of days.
Monitor for Severe Symptoms
Although brown widow venom is less toxic than black widow venom, watch for signs of a more serious systemic reaction, including:
Severe muscle cramps or spasms spreading beyond the bite area
Chest or abdominal pain
Difficulty breathing or swallowing
Nausea, vomiting, or profuse sweating
Widespread rash, swelling, or dizziness
If any of these symptoms occur, seek medical attention immediately—either call 911 or go to the nearest emergency department.
Medical Treatment
A healthcare provider may:
Administer pain control or muscle relaxants
Provide intravenous fluids for dehydration or systemic symptoms
In very rare, severe cases, administer black widow antivenom (effective for all widow species)
Evaluate for secondary infection or allergic reaction
Capture or Photograph the Spider (If Safe)
If you can do so safely, capture the spider in a sealed container or take a clear photo. This helps confirm the species for medical staff or pest control professionals. Do not risk another bite attempting this.
Prevent Future Incidents
Inspect outdoor furniture, mailboxes, and garden tools—brown widows favor sheltered spots.
Wear gloves when working in garages, sheds, or crawl spaces.
Regularly remove spider webs and egg sacs around your home.