Do not eat fish while taking cough medicine, especially deep-sea fish, to avoid causing a histamine allergic reaction, which may lead to adverse symptoms such as skin flushing, conjunctival congestion, dizziness, rapid heartbeat, and urticaria.
Professor Liu Songqing, Chief Pharmacist and Director of the Department of Pharmacy at the Southwest Hospital of the Third Military Medical University, explained that many deep-sea fish contain histamine. Once the amount of histamine in the human body exceeds the standard, this substance enters the bloodstream, causing a histamine allergic reaction. The reason why people do not experience the aforementioned symptoms after eating deep-sea fish normally is because the human gastrointestinal tract and liver contain a substance that inhibits histamine activity—monoamine oxidase. It prevents histamine from entering the bloodstream.
However, some cough medicines contain monoamine oxidase inhibitors. This means they inhibit the secretion of monoamine oxidase from the human gastrointestinal tract and liver. At this point, consuming sea fish can easily cause histamine to accumulate rapidly in the body and enter the bloodstream.
Therefore, it is best not to eat deep-sea fish while taking cough medicine. Drugs that also contain monoamine oxidase inhibitors, similar to cough medicine, include the anti-tuberculosis drug isoniazid, the anti-dysentery drug furazolidone, the antifungal drug griseofulvin, the antidepressant moclobemide, and the anti-Parkinson's drug selegiline. When taking these types of medications, you should also avoid eating deep-sea fish. It is important to emphasize that the effects of these inhibitors generally last for two weeks to be metabolized out of the body, so you should also avoid eating fish shortly after stopping the medication.
Expert interviewed: Liu Songqing, Chief Pharmacist, Professor, and Director of the Department of Pharmacy at the Southwest Hospital of the Third Military Medical University.