Ciguatera: what it is and why reef fish can make you sick

Ever felt strange after eating reef fish while traveling? Ciguatera is a food poisoning caused by ciguatoxins that build up in large reef fish like barracuda, grouper, amberjack and snapper. You can’t see, smell or taste the toxin, and cooking or freezing won’t remove it. That’s what makes it risky.

Symptoms usually show up fast — within a few hours to a day. Expect stomach symptoms first: nausea, vomiting, diarrhea and belly cramps. Within 24–48 hours many people notice odd neurological signs: tingling, numbness, a burning feeling in the hands and feet, or a strange reversal of hot and cold sensations. Fatigue, muscle aches and headaches are common too. In some people these symptoms last weeks or months.

How to spot and treat ciguatera

If you get both GI and weird nerve symptoms after eating reef fish, think ciguatera. There’s no routine blood test for it in most clinics, so doctors diagnose it from your story and the timing of symptoms.

Treatment is mostly supportive. That means staying hydrated, replacing electrolytes, and treating nausea and pain. Anti-nausea meds and IV fluids help when vomiting is severe. Some clinicians offer a single infusion of IV mannitol if a patient is seen early (within 48 hours); studies show mixed results, so it’s not a guaranteed cure but can help for some people. For persistent nerve pain or tingling, doctors may try neuropathic pain meds like gabapentin or amitriptyline. Always follow a clinician’s advice — don’t self-prescribe strong medicines.

When to get urgent care: severe dehydration from vomiting, trouble breathing, fainting, or rapid heart rate. Also see a doctor if neurological symptoms worsen or don’t improve after a few days.

Prevention and smart travel tips

Avoiding ciguatera is simpler than treating it. Don’t eat large predatory reef fish, especially if you’re in tropical or subtropical areas. Ask locals which species are risky — local fishermen often know which spots and fish carry more risk. Avoid the head, liver and roe of reef fish; toxins concentrate there. If you catch a fish yourself, beware that size matters: bigger, older fish are more likely to have toxin buildup.

If you suspect ciguatera linked to a restaurant or market, report it to local health authorities. Keeping a quick record of what you ate and where helps doctors and public health teams spot outbreaks.

Bottom line: ciguatera can be nasty and long-lasting, but you can lower your risk with simple choices. When in doubt about a reef fish, skip it — your stomach and nerves will thank you.