Last updated: July 25, 2023

Summarytoggle arrow icon

Envenomation is the exposure to a toxic substance secreted by a venomous animal, typically via a bite or sting. Clinical manifestations of envenomation depend on the specific venom and the quantity injected. Signs and symptoms range from mild local pain to neurologic compromise, coagulopathy, and cardiac arrest. Even small quantities of venom (e.g., from a bee sting) may cause life-threatening hypersensitivity reactions in susceptible individuals. Individuals who have been envenomated should always be evaluated for severe systemic reactions and receive therapy specific to the causative venom. Supportive treatment may include cardiac resuscitation, respiratory support, pain management, and/or advanced wound care. Antivenoms are available for use in the treatment of many, but not all envenomations. All antivenoms have a high risk of inducing serum sickness. Individuals who have been envenomated need to be observed for hours to weeks for delayed effects of the venom and/or the treatment. Aspects of animal bites unrelated to envenomation (e.g., infection, mechanical tissue damage) are treated in “Animal bites.”

Approach to envenomationtoggle arrow icon

Snake bitestoggle arrow icon

Epidemiology [1]

  • ∼ 5000 venomous snakebites per year in the US. [1]
  • ∼ 99% of venomous snakebites in the US are from Crotalinae snakes. [1]
  • ∼ 25% of venomous snakebites are dry (i.e., no venom is released). [2]

Overview of snake envenomation

Management of crotaline envenomation differs from coral snake envenomation. [3]

Overview of venomous snakes [3][4]
Viperidae (including the Crotalinae subfamily) Elapidae
  • Rattlesnakes
  • Coral snakes
  • Black mamba snake
Distinguishing features
  • Subtle earth-tone colored skin with rattle tail, triangular head, and vertical pupils
  • Alternating red, yellow, and black color bands
  • Long, slender, snake with a coffin-shaped head
  • All US states except Maine, Hawaii, and Alaska
  • Southern US and Northern Mexico
  • Sub-Saharan Africa
  • Cytohemoneurotoxic
  • Increases permeability of the cell membrane
  • Fibrinolytic and protein C-activation effect
  • Neurotoxin
  • Causes competitive inhibition of presynaptic and postsynaptic muscarinic AChR
Clinical features of envenomation Local
  • Painless or mildly painful bite
  • Swelling and paresthesia
  • Multiple bite sites
  • No local swelling and minimal tingling sensation

Pressure immobilization and/or tourniquets are not recommended as part of routine snake envenomation management in the US. [5]

Crotaline envenomation [4][6]

Clinical features [1][6]

Local effects are more common than systemic effects with crotaline envenomation. [6]


Crotaline antivenom is the mainstay of treatment of moderate to severe crotaline envenomation.

Crotaline envenomation management [3][4][6]
Grade Features Management

Grade 0
(no symptoms)

Grade I
(mild symptoms)

Grade II
(moderate symptoms)

  • Administer low-dose CroFab or ANAVIP.
  • Repeat CBC and coagulation panel every 1 hour until stable.
  • Monitor for at least 18 hours after symptoms are controlled.
  • ICU admission

Grade III
(severe symptoms)

  • Administer high-dose CroFab or ANAVIP. [8]
  • Repeat CBC and coagulation panel every 1 hour until stable.
  • Monitor for at least 18 hours after symptoms are controlled.
  • ICU admission

Grade IV


Crotaline antivenom

  • Types
    • Crotalidae polyvalent immune Fab (CroFab)
    • Crotalidae equine immune F(ab′)2 (ANAVIP)
  • Administration: preferably within 4 hours of the snakebite; effective for the first 24 hours [8]
  • Dosages
    • Low-dose CroFab [3][4][6]
    • High-dose CroFab [3][4][6]
    • ANAVIP [3][4][6]
  • Adverse effects: hypersensitivity, serum sickness

Coral snake envenomation [6][9]

Clinical features [1][6]


Acute management checklist for snake bitestoggle arrow icon

Spider bitestoggle arrow icon

Overview of spider envenomation [6][10][11]

Common venomous spiders
Brown recluse spider Widow spider
Distinguishing features
  • Violin-shaped marking on cephalothorax
  • Black body with variable red marks
  • North American species: red hourglass mark on ventral body
  • North and South America
  • Endemic to the Southeastern and Midwestern US
  • All continents except Antarctica
  • Necrotoxin
  • Causes local tissue necrosis
Clinical features Local
  • Painful bite
  • Red macule (initially)
  • Target-like skin lesion (late)

Abdominal pain caused by black widow spider envenomation may mimic the acute abdomen. [6][11]

Brown recluse spider envenomation [6][10]

Clinical features


Black widow spider envenomation [6][10]

Clinical features


  • Follow the general approach to envenomation.
  • Administer benzodiazepines for muscle rigidity.
  • Administer black widow spider antivenom (Antivenin (Latrodectus mactans) ) in: [6]
    • Patients with severe symptoms
    • Young children
    • Older adults
    • Pregnant individuals
  • Observe asymptomatic or mildly symptomatic patients for 6 hours.
  • Admit patients with moderate or severe symptoms.

Acute management checklist for spider bitetoggle arrow icon

Hymenoptera stingstoggle arrow icon

Hymenoptera order includes bees, wasps, hornets, and fire ants.


Clinical features [6]

  • Local effects
    • Acute pain
    • Swelling, erythema, and itching within minutes
    • Resolve within 2–3 days
    • Large local reactions: swelling and/or redness extending > 10 cm that last for days [12]
  • Systemic effects: allergic reaction, anaphylaxis

Insects of the Hymenoptera order release venom into tissue by stinging, triggering a local skin reaction and potentially life-threatening systemic reactions.

Management [6][13]

Local reactions


Massive envenomation [13][14]

  • Severe systemic reactions and/or delayed organ failure may occur after a swarm attack (typically ≥ 50 stings)
  • Perform ABCDE survey.
  • Obtain serial labs including CMP and blood pH.

Disposition [6]

Provide a prescription and training on epinephrine autoinjector use for patients being discharged after treatment of anaphylaxis from Hymenoptera stings. [6]

Scorpion stingstoggle arrow icon

Bark scorpion [6][15][16]


  • Distribution: Southwestern US
  • Pathophysiology: neurotoxins in the venom inhibit the inactivation of the sodium channels → prolonged depolarization neuronal membrane hyperexcitability

Clinical features


Centruroides scorpion envenomation management [6]
Grade Clinical features Management
  • Observe for 4–6 hours to verify no progression of symptoms. [17]
  • Administer antivenom: Centruroides scorpion immune F(ab′)2 (Anascorp)
  • Consider benzodiazepines for muscle hyperactivity if antivenom is not used.
  • Admit for symptomatic management and monitoring.

Complications [15]

Venomous aquatic animalstoggle arrow icon

The following sections cover the venomous aquatic animals most commonly responsible for hospital visits in the US, including animals not native to US waters, which may be popular among aquarists. Wounds caused by aquatic animals are particularly susceptible to infection with Vibrio species, due to contaminated seawater (see “Noncholera Vibrio infection” for more information).

Removing the patient from the water is the most important first step after any marine envenomation. [6]

Jellyfish stingstoggle arrow icon

Clinical features and treatment of jellyfish stings vary by species; clinicians should be familiar with the species commonly found in the region in which they practice. [18]

  • Pathophysiology [6]
    • Tentacles containing nematocysts attach to the skin and discharge venom.
    • Venom toxicity varies by species.
  • Clinical features [6]
  • Diagnostics: not routinely indicated
  • Management [6][18][19]
    • Follow the general approach to envenomation.
    • Inactivate remaining nematocysts. [6][19]
      • Apply vinegar to stings from Hawaiian box jellyfish, Australian box jellyfish, and Portuguese man-of-war.
      • Apply 50% baking soda slurry to lion's mane and Chesapeake Bay sea nettle.
    • Remove the attached tentacles with forceps or a gloved hand.
    • Consider antivenom administration for severe reactions from box jellyfish stings. [6]
    • Consider symptomatic relief by applying heat (e.g., heat packs, hot water immersion, warm shower). [19]

Avoid applying water to or rubbing the sting sites as this may trigger nematocysts remaining on the skin and cause additional stings. [6]

Stingray stingstoggle arrow icon

Stingray injuries may result in envenomation, but acute penetrating injuries are more common. Immediate wound management is the priority. [20][21]

Death or severe injury following a sting ray attack is usually due to penetrating trauma, not envenomation. [22]

Stonefish, scorpionfish, and lionfish stingstoggle arrow icon

Sea urchin stingstoggle arrow icon

Sea urchin injuries are usually local tissue reactions caused by spines retained in the subcutaneous tissues; significant envenomation is rare.

Clinical features [24]

Management [24]

Do not delay hot water immersion water as toxins and proteinaceous irritants are heat labile. [24]

Referencestoggle arrow icon

  1. Ruha A-M, Kleinschmidt KC, et al. The Epidemiology, Clinical Course, and Management of Snakebites in the North American Snakebite Registry. J Med Toxicol. 2017; 13 (4): p.309-320.doi: 10.1007/s13181-017-0633-5 . | Open in Read by QxMD
  2. Pucca MB, Knudsen C, S. Oliveira I, et al. Current Knowledge on Snake Dry Bites. Toxins. 2020; 12 (11): p.668.doi: 10.3390/toxins12110668 . | Open in Read by QxMD
  3. Kanaan NC, Ray J, Stewart M, et al. Wilderness Medical Society Practice Guidelines for the Treatment of Pitviper Envenomations in the United States and Canada. Wilderness Environ Med. 2015; 26 (4): p.472-487.doi: 10.1016/j.wem.2015.05.007 . | Open in Read by QxMD
  4. Lavonas EJ, Ruha A-M, Banner W, et al. Unified treatment algorithm for the management of crotaline snakebite in the United States: results of an evidence-informed consensus workshop. BMC Emerg Med. 2011; 11 (1).doi: 10.1186/1471-227x-11-2 . | Open in Read by QxMD
  5. American College of Medical Toxicology, American Academy of Clinical Toxicology, et al. Pressure immobilization after North American Crotalinae snake envenomation. Clin Toxicol. 2011; 49 (10): p.881-882.doi: 10.3109/15563650.2011.610802 . | Open in Read by QxMD
  6. Walls R, Hockberger R, Gausche-Hill M, Erickson TB, Wilcox SR. Rosen's Emergency Medicine 10th edition- Concepts and Clinical Practice E-Book. Elsevier Health Sciences ; 2022
  7. Ralph R, Faiz MA, Sharma SK, Ribeiro I, Chappuis F. Managing snakebite. BMJ. 2022: p.e057926.doi: 10.1136/bmj-2020-057926 . | Open in Read by QxMD
  8. Venomous Snakebites in the United States: Management Review and Update. Updated: April 1, 2002. Accessed: December 29, 2021.
  9. Greene S, Ruha AM, Campleman S, et al. Epidemiology, Clinical Features, and Management of Texas Coral Snake (Micrurus tener) Envenomations Reported to the North American Snakebite Registry. J Med Toxicol. 2020; 17 (1): p.51-56.doi: 10.1007/s13181-020-00806-3 . | Open in Read by QxMD
  10. Diaz JH, Leblanc KE. Common spider bites. Am Fam Physician. 2007; 75 (6): p.869-73.
  11. Vetter RS, Isbister GK. Medical Aspects of Spider Bites. Annu Rev Entomol. 2008; 53 (1): p.409-429.doi: 10.1146/annurev.ento.53.103106.093503 . | Open in Read by QxMD
  12. O’Connor A, Ruha AM. Clinical Course of Bark Scorpion Envenomation Managed Without Antivenom. J Med Toxicol. 2012; 8 (3): p.258-262.doi: 10.1007/s13181-012-0233-3 . | Open in Read by QxMD
  13. Isbister GK, Bawaskar HS. Scorpion Envenomation. N Engl J Med. 2014; 371 (5): p.457-463.doi: 10.1056/nejmra1401108 . | Open in Read by QxMD
  14. Skolnik AB, Ewald MB. Pediatric Scorpion Envenomation in the United States. Pediatr Emerg Care. 2013; 29 (1): p.98-103.doi: 10.1097/pec.0b013e31827b5733 . | Open in Read by QxMD
  15. Bilò MB, Martini M, Pravettoni V, et al. Large local reactions to Hymenoptera stings: Outcome of re‐stings in real life. Allergy. 2019; 74 (10): p.1969-1976.doi: 10.1111/all.13863 . | Open in Read by QxMD
  16. Pucca MB, Cerni FA, Oliveira IS, et al. Bee Updated: Current Knowledge on Bee Venom and Bee Envenoming Therapy. Front Immunol. 2019; 10.doi: 10.3389/fimmu.2019.02090 . | Open in Read by QxMD
  17. Rahimian R, Shirazi FM, Schmidt JO, Klotz SA. Honeybee Stings in the Era of Killer Bees: Anaphylaxis and Toxic Envenomation. Am J Med. 2020; 133 (5): p.621-626.doi: 10.1016/j.amjmed.2019.10.028 . | Open in Read by QxMD
  18. Cegolon L, Heymann W, Lange J, Mastrangelo G. Jellyfish Stings and Their Management: A Review. Mar Drugs. 2013; 11 (12): p.523-550.doi: 10.3390/md11020523 . | Open in Read by QxMD
  19. Treatment of Jellyfish Envenomation. Updated: May 15, 2014. Accessed: December 13, 2020.
  20. Diaz JH. The Evaluation, Management, and Prevention of Stingray Injuries in Travelers. Journal of Travel Medicine. 2008; 15 (2): p.102-109.doi: 10.1111/j.1708-8305.2007.00177.x . | Open in Read by QxMD
  21. Clark AT, Clark RF, Cantrell FL. A Retrospective Review of the Presentation and Treatment of Stingray Stings Reported to a Poison Control System. Am J Ther. 2017; 24 (2): p.e177-e180.doi: 10.1097/mjt.0000000000000365 . | Open in Read by QxMD
  22. Fernandez I, Valladolid G, Varon J, Sternbach G. Encounters with Venomous Sea-Life. J Emerg Med. 2011; 40 (1): p.103-112.doi: 10.1016/j.jemermed.2009.10.019 . | Open in Read by QxMD
  23. Diaz JH. Marine Scorpaenidae Envenomation in Travelers: Epidemiology, Management, and Prevention. Journal of Travel Medicine. 2015; 22 (4): p.251-258.doi: 10.1111/jtm.12206 . | Open in Read by QxMD
  24. Schwartz Z, Cohen M, Lipner SR. Sea urchin injuries: a review and clinical approach algorithm. J Dermatolog Treat. 2019; 32 (2): p.150-156.doi: 10.1080/09546634.2019.1638884 . | Open in Read by QxMD
  25. Board AR, Guy G, Jones CM, Hoots B. Trends in stimulant dispensing by age, sex, state of residence, and prescriber specialty — United States, 2014–2019. Drug Alcohol Depend. 2020; 217: p.108297.doi: 10.1016/j.drugalcdep.2020.108297 . | Open in Read by QxMD

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