Approach Considerations
Generally, the diagnosis of histamine toxicity from fish is made on clinical grounds; no laboratory tests are necessary. If proof is required for epidemiologic or other reasons, uneaten portions of the fish may be tested for histamine levels. In addition, affected patients have increased histamine levels in plasma and high levels of histamine methabolites (N- methylhistidine) in urine. [3, 12] Although these findings support the diagnosis, these measurements are poorly correlated to clinical manifestations and do not affect clinical decisions. [7]
A patient with respiratory complaints may require chest radiography to exclude foreign body aspiration or other respiratory pathology. A patient with cardiac complaints may need a cardiac evaluation that includes an electrocardiogram (ECG) to exclude other causes of palpitations or chest tightness.
One study has suggested that serum tryptase levels, if obtained very early (1-2 h) after symptom onset, may also help to make this distinction. If tryptase levels are elevated, an allergic reaction is more likely, since the tryptase level is usually within the normal range in histamine food poisoning. [18]
-
Mackerel.
-
An example of a typical histamine toxicity rash, in this case from tuna. Image courtesy of Amanda Oakley, MBChB, FRACP.
-
An example of a typical histamine toxicity rash, in this case from tuna. Image courtesy of Amanda Oakley, MBChB, FRACP.
