While Washington State is home to numerous spider species, only a very limited number pose a significant medical risk to humans. Severe reactions to spider bites are rare, and most encounters result in little to no harm. Understanding which spiders present a concern and how to react can help alleviate unnecessary worry.
Understanding Dangerous Spiders
In Washington State, the primary spider of medical concern is the Western Black Widow (Latrodectus hesperus). This spider is identifiable by its shiny black body and a distinct red or orange hourglass-shaped marking on the underside of its abdomen. Black widows typically inhabit dark, undisturbed areas such as woodpiles, sheds, garages, and basements, often spinning irregular, messy webs close to the ground.
Another spider found in Washington is the Hobo Spider (Eratigena agrestis), which is brown and known for building funnel-shaped webs. Its medical significance has been widely debated over the years. While once thought to cause severe necrotic lesions, current research suggests that most hobo spider bites result in only minor irritation, and serious effects are extremely rare. The Centers for Disease Control (CDC) no longer includes the hobo spider on its list of medically significant spiders.
A common misconception is the presence of the Brown Recluse spider (Loxosceles reclusa) in Washington State. The Brown Recluse is not native or established in Washington; its natural habitat is primarily in the Midwestern and Southern United States. Other common brown spiders in the region can resemble the Brown Recluse, leading to misidentifications.
Identifying Bite Symptoms
Symptoms from a Western Black Widow bite typically begin with immediate sharp pain at the site, sometimes described as a pinprick. This is often followed by muscle cramps, particularly in the abdomen, back, and chest, along with nausea, vomiting, sweating, and headache. A visible bite mark might be small, appearing as one or two tiny red spots.
Hobo spider bites generally cause mild symptoms. These can include localized redness, slight swelling, and itchiness, often resembling a mosquito bite. While some older reports linked hobo spider bites to necrotic lesions, current scientific understanding indicates that such severe reactions are extremely rare and often misdiagnosed, with many similar skin conditions being caused by other factors like bacterial infections.
What to Do After a Bite
If you suspect a spider bite, cleaning the affected area with mild soap and water is an important first step. Applying a cold compress or ice pack to the bite for 15 minutes each hour can help reduce pain and swelling. Elevating the bitten limb, if possible, can also be beneficial.
Medical attention should be sought if you experience severe pain, spreading redness, signs of infection such as pus or fever, or systemic symptoms like severe muscle cramps, nausea, vomiting, or difficulty breathing, especially if a black widow bite is suspected. While not always feasible or necessary, safely collecting the spider for identification can be helpful for medical professionals, but it should never delay seeking immediate care.
Preventing Spider Encounters
To minimize spider encounters, especially indoors, seal cracks and openings in your home’s foundation, around windows, and doors. Regular cleaning and decluttering, particularly in undisturbed areas like basements, attics, and garages, removes their preferred hiding spots and webs.
When working outdoors in areas like woodpiles or gardens, wear gloves and long sleeves for protection. Shake out shoes and clothing before putting them on, especially items stored in less-used areas, to prevent accidental bites. Maintaining a tidy environment inside and outside your home helps deter spiders by reducing their shelter and food sources.