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Colleen Reisz, MD    September 21, 2025

Why brown recluse bites are concentrated in certain areas

Many solitary skin lesions are attributed to brown recluse bites, although they are uncommon and typically only found in areas where the spiders are native. Kansas City is one of those native areas, as seen in the map above. They prefer warm, undisturbed areas such as attics, closets and basements. Brown recluse spiders are generally not aggressive and only bite when provoked or accidentally trapped.

• Older infrastructure: Cities like Kansas City and St. Louis, with their older buildings and basements, provide ideal hiding spots for brown recluses. These spiders are attracted to the dark, quiet and undisturbed places found in older homes.
• Abundant hiding places: The spiders gravitate toward quiet, tucked-away indoor places like closets, attics, storage rooms and basements. They will also settle into cardboard boxes, piles of laundry or behind furniture and wall hangings.
• Outdoor harborage: Outside, brown recluses can be found in woodpiles and sheds, which are common in many residential and rural areas of Missouri.
• Clutter: Areas with significant clutter, both indoors and outdoors, create numerous hiding spaces that allow brown recluse populations to thrive, increasing the chances of an accidental bite.

Key indicators of a brown recluse infestation

• Frequent sightings: The most obvious sign is seeing multiple brown recluse spiders in your home, especially in secluded, low-traffic areas like basements, closets, attics and garages.
• Irregular, messy webs: Unlike the intricate, circular webs of other spiders, brown recluses build small, messy and disorganized "retreat" webs. These are typically found in dark, hidden locations and are not used for trapping prey.
• Presence of egg sacs: Finding small, off-white, silk-covered egg sacs is a strong indication of an infestation. Each sac can contain dozens of spiderlings, allowing the population to grow rapidly.
• Consistent, unexplained bites: Waking up with repeated, unexplained bites, especially after sleeping in an infested area, is another potential sign. However, bites can be caused by many things, so this alone is not definitive proof.
• Shed exoskeletons: Brown recluses shed their skin as they grow. Finding these shed skins can confirm their presence, as they are often distinctive and can be identified by an expert.
• Other pest problems: A high number of other insects, like cockroaches or crickets, can attract brown recluses, who prey on them for food.

How to confirm an infestation

If you notice these signs, you can take a few steps to help confirm the presence of brown recluses:

• Use glue traps: Place glue boards along baseboards and in corners of basements, attics and closets. This can capture specimens for positive identification.
• Look for hiding spots: Inspect common brown recluse hiding spots, such as inside cardboard boxes, stored clothing and shoes, and behind furniture or pictures.
• Call a professional: The safest and most effective way to confirm and treat an infestation is to contact a licensed pest control professional. They have the expertise to properly identify the spiders and their hiding places. Pest control professionals use chemical and non-chemical methods like sanitation, exclusion and targeted monitoring. A single method is typically not effective against a widespread brown recluse infestation.
• Essential oils can be used, especially wintergreen, peppermint or lavender essential oil, and spray it around areas where you’ve seen a spider. You can also apply it around holes or cracks around your home to deter the spiders from coming into your home. You can also use lemon, lemongrass or wild orange essential oils but they won’t be as effective.

Immediate first aid-if you suspect you have been bitten

• Stay calm. Remaining calm helps prevent the venom from spreading through your body.
• Wash the area with mild soap and water.
• Apply a cold compress to the bite area for 10 minutes, then remove it for 10 minutes, repeating the process.
• Elevate the affected limb to minimize swelling.
• Take over-the-counter pain medication like acetaminophen (Tylenol®) if needed.
• Do not apply a tourniquet or try to suck the venom out.

When to seek immediate medical attention

Call your doctor, go to an urgent care clinic, or visit the emergency room immediately if you experience any of the following symptoms:

• Increasing and severe pain within 8 hours of the bite
• The bite develops into an open sore (ulcer) with surrounding tissue turning dark blue, purple or black
• Fever, chills, body aches or nausea
• A spreading area of redness or red streaks extending from the bite
• A widespread rash of small, flat purple and red spots
• The bite was on a small child, an older adult, or someone with a pre-existing medical condition, as they are more likely to have a severe reaction.

How a brown recluse bite progresses

A brown recluse bite can be painless at first, but symptoms often appear 2 to 8 hours later.

• The site may become red, swollen and tender.
• In some cases, a blister may form.
• In about 10% of cases, the tissue around the bite will die (necrosis), forming a hard, deep ulcer that can take months to heal and may leave a scar.

What not to do

• Do not rely on online photos for self-diagnosis. Skin lesions from other causes like MRSA infections are often mistaken for brown recluse bites.
• Do not wait to see if symptoms worsen, especially if you fall into a high-risk category or experience systemic symptoms.
• If you suspect an infestation in your home, consider contacting a licensed exterminator.