Rattlesnake Envenomation Clinical Presentation

Updated: Mar 14, 2023
  • Author: Sean P Bush, MD, FACEP; Chief Editor: Joe Alcock, MD, MS  more...
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All or none of the following may be present. Note that symptoms are subject to change, and this change can be very rapid or very insidious. In addition, severity is generally guided by the most severely affected parameter. [9, 11, 12, 13, 14] See the following:

  • Pain around the bite site

  • Swelling

  • Taste changes (eg, a metallic taste)

  • Difficulty breathing

  • Chest pain

  • Nausea, vomiting, or diarrhea

  • Hematemesis, hematochezia

  • Neurologic symptoms - Weakness, paresthesias

  • Syncope, near syncope


Physical Examination

Physical examination findings may include the following:

  • Fang marks - May be 1, 2, or more, or may be unable to discern (See the image below.)

    Moderate rattlesnake envenomation in a toddler aft Moderate rattlesnake envenomation in a toddler after treatment with antivenom. Photo by Sean Bush, MD.
  • Tenderness surrounding the bite site

  • Local edema: Use a pen to mark and time the border of advancing edema every 15-20 minutes initially. Once stabilization with antivenom has occurred, repeat measurements every 1-2 hours. Rapidly progressive swelling is usually indicative of a severe envenomation.

  • Erythema

  • Ecchymosis

  • Bullae

  • Bleeding

  • Hypotension/hypertension

  • Tachycardia

  • Myokymia (muscle fasciculations)

  • Neurologic effects

  • Lethargy



Complications of snake envenomation may include the following:

  • Bleeding, such as gastrointestinal or intracranial

  • Compartment syndrome

  • Necrosis with resulting tissue loss or loss of function

  • Rhabdomyolysis, myoglobinuric renal failure

  • Infection

  • Respiratory difficulty

  • Death (rare in the United States)

  • Antivenom-associated anaphylaxis  - Type I (immediate) hypersensitivity reaction, which may be life threatening; characterized by urticaria, airway swelling, wheezing, and shock

  • Antivenom-associated serum sickness - Type III (delayed) hypersensitivity reaction; characterized by fever, urticaria, lymphadenopathy, and arthritis and may occur 3 days to 3 weeks after antivenom