UMEM Educational Pearls

Title: Fishy Information from Undersea Medicine

Posted: 12/29/2025 by TJ Gregory, MD
Click here to contact TJ Gregory, MD

Winter is in full swing and an escape to warmer climes is the only answer for many. That also means enjoying local tropical seafood and associated toxins. How do you differentiate, manage, and properly recognize the ABEM prompt?

Scombroid - HISTAMINE reaction

Native histidine conversion to histamine due to improper freezing (>40° F)
Mimics seafood allergy
Treat with oral antihistamines.
Histamine source is external, not internal production as in allergy, so no role for steroids or epinephrine
Buzzwords: mackerel, tuna, bonito, albacore, sardines, anchovies, mahi-mahi, amberjacks, marlin and herring
Buzzwords: spicy, peppery, or bubbly taste; honeycomb appearance of fish skin

Ciguatera - CIGUATOXIN contaminated reef fish

Phytoplankton produce ciguatoxin. Little fish eat phytoplankton. Big fish eat little fish. Humans eat big fish where toxin has accumulated.
Symptoms within hours of ingestion. Lasting weeks to years or rarely life-long.
GI: N/V/D, abdominal pain
Neurologic: ataxia, paresthesia, allodynia. Careful of mimicking MS or DCS
No treatment. Supportive care per clinical effects
Endemic in Australia, the Caribbean and the South Pacific islands.
Barracuda, grouper, snapper, parrotfish, moray eels, triggerfish and amberjacks.
Odorless, tasteless and heat-resistant—fish will not taste different, cooking will not prevent intoxication.
Buzzwords: hot/cold sensation inversion; persistent itching worse with skin warming, e.g. from alcohol or exercise

References

Chapter 3: Seafood Poisonings - Divers Alert Network