Over the past few decades, many researchers and medical experts have studied trimethylaminuria, an interesting condition genetic condition. This rare metabolic disorder prevents the body from creating a specific enzyme. Without this enzyme, a person exudes a powerful fishy odor or strong body odor. As you might imagine, the disorder has earned many descriptive nicknames, including fish odor syndrome and fish malodor syndrome.


Most cases of trimethylaminuria are the result of mutations in the FMO3 gene that instructs the body on how to create the enzyme that breaks down compounds containing nitrogen, like trimethylamine. Because of the mutation, the body never creates the enzyme, and as such, compounds are not converted to less odorous alternatives. To correct for this, the body releases the fishy-smelling trimethylamine any way it can, most often through sweat, breath, and urine. Occasionally, trimethylaminuria occurs in people without gene mutations. Diet, hormone imbalances, or high levels of trimethylamine-producing bacteria can cause the issue, as well.

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A fishy odor is the single characteristic of trimethylaminuria. Some people give off a constant odor, though, for most, the scent varies in intensity. Actions that cause a person to sweat more, such as exercising or stress, may worsen the smell. Additionally, females may notice that the odor intensifies before and during menstruation. Most people have no other symptoms, though there are cases of anemia, increased spleen size, and low blood neutrophil counts.

foul fishy odor symptoms Ake Ngiamsanguan / Getty Images


Social Aspects

Trimethylaminuria’s fishy smell can have many social and psychological effects. Records show that one of the most common conditions to occur alongside trimethylaminuria is depression. Many people who have the disorder feel self-conscious about their smell and shy away from social situations. Individuals with trimethylaminuria sometimes can only smell their odor while urinating, so they cannot judge its intensity. This leads to constant self-doubt and worry.

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Affected People

In general, females are more likely to have trimethylaminuria than males, though scientists are still unsure why this is the case. Some researchers suggest female sex hormones may trigger and aggravate trimethylaminuria. This coincides with the disorder worsening during puberty, menstrual periods, and menopause. Alternatively, some researchers suggest that there are multiple types of trimethylaminuria and that belief to the contrary is slowing the development of treatments.

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Physicians will usually perform diagnostic evaluations on individuals who have the characteristic fishy odor, including urine and genetic tests. Doctors use the former to measure the level of trimethylamine in the urine. If it is significantly higher than average, they can diagnose the disorder. Some people undergo genetic testing, with the goal of identifying mutations that affect the FMO3 gene.

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Possible False Positives

Though trimethylaminuria is a distinct condition, doctors often make mistakes when diagnosing it. The most common misdiagnoses come when a patient's urine is high in trimethylamine due to another condition. Urinary tract infections, cervical cancer, bacterial vaginosis, and advanced liver or kidney issues can all cause high trimethylamine levels and give a false positive during urine tests. The Aerococcus urinae bacterium can also cause a fishy odor in urine, particularly in children.

false positive liver issues Jan-Otto / Getty Images


Treatment Options

Currently, there is no official cure or treatment for trimethylaminuria. Because most people have no symptoms other than the odor, doctors regard the condition as benign. Physicians also tend not to recognize the disorder, leading to slower or missed diagnoses. Because there are no common treatments, individuals with trimethylaminuria often try to mask the smell. Some use beauty and hygiene products, while others take up smoking. At least one study suggests activated charcoal supplements; participants found the pills reduced or eradicated the fishy odor.

activated charcoal supplements Trexdigital / Getty Images


Foods to Avoid and Lifestyle Changes

Though there are no official treatments, some researchers suggest dietary changes to, in theory, reduce the intensity of the fishy odor. Egg yolks, red meats, fish, beans, and legumes are all foods people with trimethylaminuria should avoid due to a high content of carnitine, nitrogen, sulfur, lecithin, or choline. Some experts suggest washing clothing in slightly acidic detergent with a pH between 5.5 and 6.5 to help combat the odor.

red meat fish avoid nehopelon / Getty Images



Many people with trimethylaminuria worry about passing on their condition to their children. Most cases of trimethylaminuria appear to have an autosomal recessive inheritance pattern. This means that both parents must be carriers of a cell that has an altered gene, though they do not have the condition themselves. In such cases, a child has a one in four chance of having the condition and a two in four chance of being a carrier. Rarely, carriers have temporary episodes of strong body odor.

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Because most people with trimethylaminuria have only the singular symptom, they have normal life expectancies. However, it’s important not to neglect the extreme social and psychological issues that accompany the condition. Individuals who live with trimethylaminuria for a long time are more likely to become socially reclusive, show signs of low self-esteem, and have suicidal tendencies. Friends and family of those with the condition should remain encouraging and understand that there is little a person can do to manage the odor.

prognosis encouraging understand family HRAUN / Getty Images


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