Experts remind that you should not eat fish while taking cough medicine, especially deep-sea fish, to avoid causing a histamine allergic reaction, which may lead to symptoms such as skin flushing, conjunctival congestion, dizziness, rapid heartbeat, and hives.
The human gut 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, which suppress the secretion of monoamine oxidase by the gut and liver. Many deep-sea fish contain histamine. Once the amount of histamine in the body exceeds the limit, this substance can enter the bloodstream, triggering a histamine allergic reaction.
Therefore, it is best to avoid eating deep-sea fish while taking cough medicine. Other drugs that also inhibit monoamine oxidase, 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. Some traditional Chinese medicines can also inhibit monoamine oxidase, such as deer antler, hawthorn, and fleeceflower root. It is also important not to eat deep-sea fish when taking these types of medication. It should be emphasized 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 for a short period after stopping the medication.
In addition, many people take cough medicine before bed to avoid affecting their sleep. However, this often has the opposite effect. For people with a cough and phlegm, taking cough medicine can cause phlegm to remain in the respiratory tract. Taking it before bed can further obstruct the airways and suddenly worsen the cough.