What you should know about spider bites




As the weather gets cooler, spiders may come inside and here are some tips you should know about spider bites.

There are two medically important families of spiders.  Theridiidae (or widow spiders) and Loxoscelidae (or brown recluse spiders).

  • When black widow spiders bite it may feel like a sharp pinch with subsequent pain that develops over the next 30 minutes.The bite site may be surrounded by pale skin and then ringed with red.  The patient may also have systemic symptoms over the next 60 minutes or abdominal pain, sweating, nausea, vomiting, seizures and, very rarely, death.  If left untreated, symptoms resolve within 48 hours.
  • The bite of a brown recluse spider is often undetected with pain beginning over the next several hours.  The bite site may develop a blue macule or a characteristic red lesion with surrounding pale skin and then ringed with area of blue skin.  Over the next week a scab may develop and then fall off.  Systemic symptoms associated with a brown recluse bite are a flu-like illness with fever, headache and fatigue.  Rarely, patients can have muscle and blood breakdown and kidney failure.

What blood work do you need?

  • Black widow bite needs no labs.
  • Brown recluse (if severe envenomation suspected with systemic symptoms) may need complete blood count, electrolytes, kidney functioning and blood and muscle lab work if concerned about muscle and blood breakdown.

How can your physician confirm the diagnosis?  This is a clinical diagnosis, meaning no lab is needed for diagnosis.

What is spider bite treatment?

  • Black widow treatment includes local wound care including ice and elevation.  Watch for infection.  Tetanus vaccine should be given.  Pain medicine and muscle relaxants to be given, when needed.  An antivenom is available and considered for severe envenomation.
  • Brown recluse treatment also includes local wound care including ice and elevation  pain medicine.  Tetanus vaccine.  Antibiotics are not indicated unless the skin surrounding appears infected.  If there is significant skin sloughing, excision of skin may be warranted.

How to avoid a spider bite?

  1. Be aware that spiders prefer warmer temperature and they gravitate to dark locations like a shoe, glove and infrequently used clothing.
  2. Consider shaking out gloves, clothes, and shoes before putting them on.
  3. Wear long-sleeved shirts and pants outdoors (to avoid unearthing spiders under rocks and logs).

I hope this helps.

About drlesliegreenberg

I have been practicing as a family physician for over 20 years--as both an educator of physicians and clinician. From infancy to the elderly, I perform obstetrics and general medicine. I love my career and am passionate about my field of knowledge and my patients. Follow me on Facebook at Leslie Md Greenberg Medical Disclaimer The content of this website is provided for general informational purposes only and is not intended as, nor should it be considered a substitute for, professional medical advice. Do not use the information on this website for diagnosing or treating any medical or health condition. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider.
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