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Fish Odour Syndrome: Symptoms, Causes, Diagnosis & Treatment

By Nupur Jha

Fish odour syndrome which is also known as trimethylaminuria, is a rare genetic disease. As the name suggests, the breath, sweat, reproductive fluids and urine of the person having this disorder smell of rotten fish. The symptoms of this genetic disorder can be detected in the person soon after his birth.

People suffering from this disorder face social as well as psychological difficulties such as depression. Apart from having a foul smell, no other health issues as such are faced by the people due to this disorder. As per the findings, women seem to be more affected by this genetic disease.


There are no specific symptoms of this genetic disorder, people having this syndrome appear healthy like any other normal person. The foul smell is the only way to detect whether someone is suffering from it or not. Genetic test and urine test can be done to detect whether a person has the fish odour syndrome or not.

What Causes Fish Odour Syndrome?

This syndrome is a metabolic disorder which is caused due to mutation of the FMO3 gene. This gene instructs the body to secrete the enzyme that breaks down compounds which contain nitrogen, like trimethylamine (TMA). This compound is hygroscopic, flammable, transparent and has a fishy odour. Presence of this organic compound in excess in the body causes this rare genetic disease.

The foul smell produced due to this disease differs from person to person, while some have a very strong smell others may smell lesser than them. The odour can become worse when you are:

  • Sweating post working out
  • Emotionally upset
  • Stressed out

This condition can worsen in women before and during their menstrual cycles and also during menopause and when they consume contraceptive pills.


The fish odour syndrome is diagnosed with the help of a urine test and a genetic test.

Urine Test - The trimethylamine level present in the urine is scaled, people with high levels of this organic compound are diagnosed with this disease. The person is given a dose of choline to drink via mouth prior to the urine test.

Genetic Test - In the genetic test the FMO3 gene is tested, whose mutation leads to this disorder. Carrier testing is another method which is used to detect genetic disorders like these.


This genetic condition has no cure but following certain tips can aid in reducing the odour and managing the mental trauma one faces in the society.

Here are a few things you should do to reduce the odour:

  • Foods such as fish, egg yolk, red meat, beans, legumes etc., which contain trimethylamine, choline, nitrogen, carnitine, lecithin and sulfur should be avoided as they can trigger the foul smell.
  • Consumption of antibiotics like metronidazole and neomycin aid in reducing the amount of trimethylamine produced in the intestine by the gut bacteria.
  • Consume more of riboflavin (Vitamin B2), it triggers FMO3 enzyme activity which helps in breaking down the organic compound trimethylamine in the body.
  • Eat foods that have a laxative effect as it helps in reducing the time the food remains in the gut.
  • Supplements such as activated charcoal and copper chlorophyllin aid in depletion of trimethylamine in the urine.
  • Avoid all activities like exercising, getting stressed, etc., which lead to sweating.
  • Use soaps with moderate pH levels which range between 5.5 and 6.5, this will help in removing the trimethylamine present on the skin and reduce the smell.

Some more tips to cope with this rare genetic condition are:

  • Getting counselled to deal with psychological conditions like depression.
  • Genetic counselling can help you in understanding this disorder and its root cause, this will aid in understanding the risks your offspring will be prone to and the precautions you should take.
Read more about: disorder genetic disease health
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