Eating fish is generally considered to be healthy. However, as with almost all rules, there are exceptions. A 50-year-old woman experienced an adverse reaction after eating a lightly seared tuna steak in a restaurant. Professor Markus Wörnle, an emergency medicine physician from Ludwig Maximilians University, Munich, described her case.
The Patient and Her Story
According to Wörnle, the patient developed redness on her face, neck, and arms a few minutes after eating the fish. She also felt a slight tingling throughout her body, as well as dizziness and a feeling of constriction. She had never experienced these symptoms before and had no allergies. She had regularly eaten tuna without any problems.
Findings, Diagnosis, and Treatment
- Blood pressure: 94/56 mmHg
- Heart rate: 73/min
- Respiratory rate: 13/min
- Temperature: 36.8°C
- Pale rash on the face, neck, trunk, and upper extremity
- Further physical examination and laboratory diagnostics: normal
- Diagnosis: histamine poisoning
- Treatment: intravenous dimetindene (4 mg), prednisolone (250 mg), and Ringer's infusion solution (1000 ml), resulting in rapid improvement symptom-free hospital discharge.
Discussion
Histamine or scombroid poisoning is, according to Wörnle, the most common fish poisoning worldwide. It is caused by the consumption of histamine-contaminated fish from the Scombridae family, which includes tunas and mackerels. Other fish not belonging to the Scombridae family, such as sardines, bluefish, and rarely salmon, can also lead to histamine poisoning. Histamine poisoning occurs when the cold chain is broken, allowing bacteria in the fish tissue to multiply. These bacteria convert histidine into histamine. According to Wörnle, histamine is also produced in various organs in the human body, including mast cells and basophilic granulocytes. During allergic reactions, endogenous histamine is released. The histamine produced in fish poisoning is absorbed through the gastrointestinal tract following consumption, leading to a clinical reaction indistinguishable from an allergy.
Cases of histamine poisoning are likely underestimated, as they are often misdiagnosed as allergic reactions and there is no systematic scientific recording of such events. De novo fish allergies in adults, however, are rare, with a prevalence estimated at 0.6%.
The treatment of patients with scombroid poisoning does not differ in practice from the treatment of anaphylaxis. A key component of treatment is the use of antihistamines. The current German guideline on acute therapy and management of anaphylaxis recommends treatment with dimetindene (1 mg/10 kg body weight). Alternatively, two ampoules (8 mg) can be given for a weight-adjusted dose.
Fish poisonings can be severe. For example, a 46-year-old man experienced a rare case of botulism after consuming improperly stored herring. The man, who lived in Germany after moving from Ukraine, presented with abdominal complaints. His wife reported that he had collapsed the previous day, vomited, and complained of abdominal pain. The patient also described double vision and a swallowing disorder.
Cerebral computed tomography and cerebrospinal fluid diagnostics were normal. Notably, he had bilateral ptosis, mid-dilated pupils unresponsive to light, rapidly progressive tetraparesis, and respiratory insufficiency. As previously reported by Univadis, this was a rare case of botulism due to improper storage of herring fillets past their expiration date.
Ciguatera poisoning, resulting from the consumption of certain tropical fish, is also dangerous. It involves ciguatoxin, a toxin produced by algae found on coral reefs or seaweed. The algae are eaten by small fish, which are then consumed by larger fish (especially barracudas, mackerels, snappers, and groupers). Humans become ill from consuming poisoned fish. The toxins do not harm the fish themselves and are tasteless and heat-resistant. It is estimated that at least 50,000 cases of ciguatera occur worldwide each year. However, since the condition is often not recognized as such, this number is likely much higher. For humans, ciguatoxin is a potent toxin that primarily affects the nervous system. Symptoms such as skin redness, numbness of the lips and oral mucosa, nausea, vomiting, and diarrhoea develop up to 48 hours after consuming the fish. Due to the high affinity of the toxins for neuronal sodium channels, neurological symptoms are characteristic of ciguatera poisoning. Neurological symptoms, such as cold allodynia, dizziness, tingling, visual disturbances, muscle cramps, and a burning sensation when exposed to cold, can last for weeks or months.
This story was translated from Univadis Germany, which is part of the Medscape professional network, using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.