April 5, 2021: How Do You Differentiate Ciguatera Poisoning from Scrombroid Poisoning?

Distinguishing between symptoms of ciguatera vs scrombroid poisoning is important as treatment is different. Even if you live in a land-locked area, fresh fish is easily transported to restaurants/grocery stores, so  patients will present with these marine poisonings.  BTW, the etiology of scrombroid poisoning was discovered by Vanderbilt clinical pharmacologists who ate the same fish and developed the same symptoms.  They collected their urine and analyzed it for histamine.  The rest is history and documented in the NEJM.

Attached is an excellent monograph that compares the two poisonings.

Fish Poisonings Marine Envenomations Infographic - PDF


  • Dinoflagellate adheres to algae and passed up food chain when herbivorous fish eat the organism
  • Fish not affected but are eaten by carnivorous fish which are eaten by humans
  • 400 fish which harbor the toxin in their viscera, skin and musculature
    • Barracuda, amberjack, dolphin, moray eel, surgeonfish, grouper, red snapper
  • Toxin (ciguatoxin) highly stable; not inactivated by heating, drying cooking or freezing.
  • Induces membrane depolarization in n tissue by opening Na channels
  • Excess neural discharge followed by blockade of nerve conduction
  • Inhibits uptake of GABA



  • V/D abdominal pain 2-12 hours after consumption followed by neurologic symptoms
  • Paresthesia of perioral and distal extremities especially palms and soles
  • Cold to hot sensation reversal
  • Ataxia, Headache, arthralgias, vertigo
  • Hypotension/bradycardia (unusual)
  • Treatment is supportive-(symptoms may last for weeks)


  • Consumption of spoiled fish which have undergone autolytic changes secondary to improper storage
  • Scrombroid-tuna, mackerel, bonito, mahi mahi, bluefish, amberjack, sardines
  • Histamine increased in spoiled fish which causes clinical syndrome
  • Toxin heat stable
  • Fish with high concentration red meat which becomes brown when cooked have high concentration of  histidine in muscle
  • Bacteria which reside in the gills and GI tract of fish contain an enzyme (histadine decarboxylase) which decarboxylates histadine into histamine

graphic 2021

  • Bacteria- Enterobacteriaceae, Shigella, Salmonella, E. coli, Klebsiella, Proteus
  • Histamine
    • vasoactive amine, stored primarily in mast cells
    • Antigen binding to IgE on surface of mast cells causes degranulation
    • Histamine causes local vasodilation and smooth muscle contraction


  • Hot, blotchy flushing of skin
  • Demarcated borders of face, neck, upper chest
  • Nausea, vomiting, diarrhea
  • Peppery taste
  • Tingling sensation mouth/legs
  • Symptoms usually resolve 6-8 hours but can be longer
  • Diagnosis is usually made on purely clinical grounds
  • Treatment is antihistamine administration


This question was prepared by Donna Seger.  The monograph was prepared by Elizabeth Burnham, Pharm D Candidate 2021; Lipscomb University College of Pharmacy.

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@vumc.org.



Donna Seger, MD

Executive Director

Tennessee Poison Center


Poison Help Hotline: 1-800-222-1222