Coral Snake Envenomation Clinical Presentation

Updated: Aug 14, 2017
  • Author: Robert L Norris, MD; Chief Editor: Joe Alcock, MD, MS  more...
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The vast majority of patients bitten by coral snakes report that a brightly colored snake bit them.

North of Mexico City, including the United States, the color pattern of the snake can be helpful in differentiating a coral snake from a harmless mimic (eg, nonvenomous milk snake). In this region, all coral snakes have a red, yellow, black, yellow, red banding pattern (every other band is yellow; red and yellow bands touching, and bands completely encircle the body; see the image below); most harmless mimics have a red, black, yellow, black, red pattern (every other band is black; red and yellow separated by black; and/or some bands do not completely encircle the body). [6] The mnemonic "Red on yellow, kill a fellow; red on black, venom lack," may be helpful in this region. South of Mexico City, the banding patterns are much less helpful, and bicolor (red and black) species are also present.

Snake envenomations, coral. Comparison of the harm Snake envenomations, coral. Comparison of the harmless Lampropeltis triangulum annulata(Mexican milksnake) (top) with Micrurus tener(Texas coral snake) (bottom). Photo by Charles Alfaro.

History may include the following:

  • Onset of symptoms may be delayed up to 10-12 hours but may then be rapidly progressive.

  • Paucity of local complaints

  • Local paresthesias (may be painful)

  • Soft tissue swelling (usually mild)

  • Alteration of mental status

  • Complaints related to cranial nerve dysfunction (eg, diplopia, ptosis, difficulty swallowing)


Physical Examination

Impending respiratory failure signs and symptoms include the following:

  • Respiratory distress

  • Pharyngeal spasm

  • Hypersalivation

  • Cyanosis

  • Trismus

Neurologic dysfunction signs and symptoms include the following:

  • Altered mental status

  • Ptosis

  • Generalized weakness

  • Muscle fasciculations

Cardiovascular collapse signs and symptoms include the following:

  • Hypotension

  • Tachycardia

In addition to a brief generalized examination, the skin should be carefully examined in an effort to identify what may be very tiny puncture wounds at the bite site.  These may be hard to see.  Generally, there is little in the way of other local findings (little bleeding, ecchymosis or swelling).

A careful neurological examination should be done in an effort to identify any evidence of early venom-induced dysfunction.  Particular attention should be paid to the cranial nerves (watching for any evidence of bulbar weakness) and to motor strength (including respiratory muscles).



Complications of snake bite may include the following:

  • Respiratory failure
  • Aspiration

  • Cardiovascular collapse

  • Prolonged neuromuscular weakness