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 may
Black widow spiders are frequently found in low-lying
webs in garages, 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
What are the signs and symptoms of a black widow spider bite?
In most cases of a black widow spider bite, symptoms
consist only of:
Minimal to sharp pain followed by swelling
and redness at the site of the bite.
One or two small fang marks
like tiny red spots.
In some cases, severe symptoms appear within 30 to 60
minutes. These include:
Muscle cramps and spasms that start near the bite and then
spread and increase in severity for 6 to 12 hours.
nausea, or vomiting.
Severe belly, back,
or chest pain.
Stupor, restlessness, or
Severe high blood pressure.
What should I do if a black widow spider bites me?
If you believe you have been bitten by a
black widow spider:
Get medical help immediately. Call your doctor, hospital, or poison control
Remain calm. Too much excitement or movement will increase
the flow of venom into the blood.
Apply ice to the bite
Do not apply a tourniquet. It may cause more harm than
Try to positively identify the spider or catch it to
confirm its type.
How is a black widow spider bite diagnosed?
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.
How is it treated?
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 or high blood
pressure, or you are pregnant.
Treatment also includes:
Medicine for pain and spasms. Pain and spasms
may be severe enough to require
benzodiazepines, such as lorazepam (Ativan) or
diazepam (Valium), or narcotics, such as morphine or
fentanyl. Calcium may also be used.
Antihypertension medicines for high blood
How this information was developed to help you make better health decisions.