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Black widow spiders ( Latrodectus mactans and Latrodectus hesperus) are found throughout the United States, Mexico, and southern Canada. A female black widow is much more likely to deliver more venom than a male spider. Female black widows are long-legged, shiny, coal-black spiders with an orange, red, or yellow shape on their underside that usually looks like an hourglass but may be another shape. Female black widows are usually about 1.5 in. (3.8 cm) long, but they may be smaller.
Black widow spiders are frequently found in low-lying webs in garages, in barbecue grills, around swimming pools, and in wood piles. Most bites occur in rural and suburban areas and occur between the months of April and October. These spiders tend to bite defensively when their webs are disturbed. Bites to babies and children may be more serious than bites to adults.
In most cases of a black widow spider bite, symptoms consist only of:
In some cases, severe symptoms appear within 30 to 60 minutes. These include:
If you believe you have been bitten by a black widow spider:
A black widow spider bite is diagnosed through a physical examination and questions about the bite. You should be prepared to describe the spider, where and when the bite took place, and what you were doing at the time. Your doctor will ask what your main symptoms are, when they began, and how they have developed, progressed, or changed since the bite.
Medicine to counteract black widow spider venom (antivenom) is available in the United States, Mexico, and Canada. It is usually used if you have trouble breathing, have high blood pressure, or are pregnant.
Treatment also includes:
ByHealthwise StaffPrimary Medical ReviewerWilliam H. Blahd, Jr., MD, FACEP - Emergency MedicineAdam Husney, MD - Family MedicineKathleen Romito, MD - Family MedicineSpecialist Medical ReviewerH. Michael O'Connor, MD, MMEd, FRCPC - Emergency Medicine
Current as ofNovember 20, 2017
Current as of: November 20, 2017
Author: Healthwise Staff
Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & Adam Husney, MD - Family Medicine & Kathleen Romito, MD - Family Medicine & H. Michael O'Connor, MD, MMEd, FRCPC - Emergency Medicine
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