April 20, 2015: Venomous spiders to watch out for in your home: what should you do if bitten by a spider?

Most spider bites are harmless as there are many non-venomous spiders that bite and may cause some minor local redness and pain. These bites can usually be managed at home by washing, applying ice, and keeping the area clean.

The two venomous spiders common to this area are the Black Widow and the Brown Recluse spiders.

BLACK WIDOW SPIDER ( Latrodectus Mactans) :

The Black Widow spider is glossy black in color, and identifiable by a reddish or orange colored hour glass marking on the abdomen.

Picture of the underside of a black widow spider and an egg sack 


Where are they found?  Black widow spiders are usually found in areas that are dark such as crawl spaces, water meter compartments, inside boxes and in firewood piles.

What are the local symptoms?  Victims may not realize they have been bitten by a black widow spider as a bite usually feels like a pinprick with minimal local reaction. There may be some immediate pain, burning and redness at the bite site, which usually resolves quickly.

Systemic effects may start in 2 to 4 hours after the bite and can include painful muscle cramping and fasciculation of the involved extremity. This can progress to severe muscle pain and cramping of the chest, back or abdomen muscles, and may lead to a board-like rigidity. Other symptoms can include headache, nausea, vomiting, muscle weakness, dyspnea, and paresthesias. Changes to heart rate and blood pressure may also be noted. 

TN poison center recommends:

Home care: Wash bite area with soap and water, can apply ice and get a tetanus booster if needed.

If systemic symptoms are noted, the patient will need to be monitored at a hospital, and treated with muscle relaxers, narcotics or benzodiazepines. Antivenom is usually not recommended due to high risk of adverse effects.

BROWN RECLUSE SPIDER (Loxosceles Reclusa):

The Brown Recluse spiders are native to Midwestern and Southeastern states, they are not aggressive and bite only if threatened. It is a medium sized spider that may be light yellowish brown to dark brown in color, and is distinguished by the characteristic violin shaped mark on the back and it has only 3 pairs of eyes unlike other spiders.


Brown recluse spiders are notable for their characteristic violin pattern on the back.

brown recluse compared to a penny 


Where are they found?  They seek out dark, warm, dry environments such as attics, closets, porches, barns, basements, woodpiles, and old tires.

What are the local symptoms? The bite may cause mild stinging or pain, and will worsen becoming painful and itchy in the next 2-8 hours. This is followed by an area of erythema that is pruritic followed by the development of an extremely painful area which is usually blue or purplish in color, surrounded by grayish ring surrounded by a red outer ring in a typical “bulls eye” pattern. Vesicles or bullae may develop at the bite site. This tissue may eventually develop a black eschar (necrotic arachnidism).

Systemic Loxsoscelism:  The syndrome consists of fever, rash, myalgia, and hemolysis, and usually develops in 24 - 72 hours after the bite. 

TN poison center recommends:

Home care: Wash the area with soap and water and can apply ice. Tetanus booster if needed. No ointments, no debridement, no dapsone and no steroids are recommended. The bites usually heal very well if they are kept clean and dry and left alone. 

Systemic effects: If systemic symptoms are noted, patient will need to have urine dipped to test for the presence of hemoglobin/ blood. If the urine dip is positive for blood and/or the patient has signs of systemic loxsoscelism (rash,fever), the patient should be admitted to be observed for hemolysis. This is especially important in children < 12 years of age as toxin induced hemolysis can occur very rapidly.


This question prepared by:  Suparna Kumar, CSPI  (Poison Information Specialist)


I am interested in any questions you would like answered in the Question of the Week.  Please email me with any suggestion at donna.seger@vanderbilt.edu


Donna Seger, MD

Medical Director

Tennessee Poison Center


Poison Help Hotline: 1-800-222-1222