This is what it’s like to live with fish odor syndrome: “People change seats”

Juan, 56 years old, always attributed the social isolation he suffered as a child to his sexual orientation. At that time, liking boys was not something accepted among his peers. Over time, he understood that there was another factor that also marked that stage: “In elementary school, my classmates told me I smelled bad, but I ended up normalizing it. You know there is something that sets you apart from the rest, but you never consider that there might be a disease behind it,” explains this man, whose name has been changed to preserve his anonymity.

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Years ago, he learned to choose seats with free space around him and close to the exit. It was not a quirk. It was an escape from receiving unpleasant comments, outbursts, or pointing fingers at him. He even thought his hygiene was poor or simply not good. But nothing could be further from the truth.

That very particular smell, which has accompanied him all his life, is a disease and has a name: trimethylaminuria (TMAU), known as fish odor syndrome. It is a metabolic disorder caused, in most cases, by a genetic alteration.

“People who suffer from it have a liver enzyme, called FMO3, that does not function properly, and therefore, their body cannot eliminate a substance called trimethylamine. This substance is naturally generated when the bacteria in the intestine digest certain foods. Under normal conditions, the liver transforms it into another odorless substance so the body can eliminate it. But when that enzyme fails, trimethylamine is expelled untransformed, so the smell appears in the breath, sweat, or urine with that characteristic fishy odor,” details Beatriz Mínguez, pediatrician at the Sant Joan de Déu hospital who treats TMAU patients.

But it is not the only manifestation. In fact, Juan even emits, according to his own explanation, a smell similar to that of a tanker truck when it opens the sewer to empty the cesspool. It is estimated that there is one case per every 100,000 to 200,000 people, although its exact prevalence is difficult to determine due to significant underdiagnosis. The diagnosis is confirmed through a genetic blood test and a urine test that measures trimethylamine levels in the body.

Juan got answers two years ago. After going to his primary care doctor and sharing his suspicions, they performed a test. All parameters came out normal except for trimethylamine, which was at the limit. In his case, the smell is emitted through sweat or increased perspiration, which can be triggered by stress or emotional situations.

“Every time I’m about to board a plane, I get a little more nervous, even though I’m used to it. It is common for the person sitting next to me to start moving restlessly, get up, and end up asking the crew if there is any free seat,” he recounts. Not even going freshly showered, wearing new clothes, or applying moisturizer manages to avoid these situations.

This is not an isolated episode. The disease has also affected his work life. Some colleagues have made comments in front of him “without holding back at all,” while others have covered their noses in his presence. “We are talking about people who, in theory, are used to living with diversity and educating in empathy,” laments Juan, a high school teacher.

At the last center where he is currently working, he decided to address the issue from day one. He explained to his coworkers that he had trimethylaminuria. “Telling it is like coming out of the closet again.” If dealing with adults’ reactions is already complicated, doing so with “unfiltered” teenagers is even more so.

One of the episodes he remembers most happened in a high school class. “Before starting an activity, one student said to another: ‘Now he’s going to start smelling bad.’ She had noticed that when I got excited explaining literature, the smell intensified.” Since that day, that student, who always sat in the front row, started sitting at the back of the classroom.

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Rosa, a 35-year-old woman, who has wanted to offer her testimony under the condition of not specifying her name or profession. “I tried to fight for a normal life, surrounded by people, doing physical activity I liked… But I was subjected to so much school and workplace bullying that I ended up with severe depressive disorders.” This woman has seen many specialists to treat the post-traumatic disorder and generalized anxiety caused by the bullying. And she adds: “I will never know what my life would have been like without this disease and without the bullying I received.”

For years, she went to consultations in different specialties without finding an answer. The diagnosis did not come until much later, when, after contacting other affected people and insisting on being tested, an endocrinologist confirmed she had trimethylaminuria. Knowing her diagnosis was “liberating” because “I could finally put a specific name” to what was happening to her.

Stress, anxiety, heat, or intense physical exercise are some of the factors that can intensify the smell. At least, in Rosa’s case. More generally, it occurs when consuming certain foods, especially fish, seafood, and others rich in choline. “There are patients who improve by regulating their diet and avoiding certain foods,” explains Mínguez. In some cases, treatment is complemented with vitamins or antibiotics, although none of these measures provide a definitive solution.

Rosa believes the smell “has decreased with age,” although she does not know for sure because she does not perceive her own smell with the same intensity as those around her. “However, the most determining factor in my experience is the anxiety derived from living with social rejection. It is a difficult circle to break: smell, social rejection, increased anxiety, and again more intensity of symptoms,” she summarizes.

Eurofragance, a multinational fragrance company, created last June together with the dermocosmetic laboratory MartiDerm a collection of cosmetics aimed at improving the quality of life of people with trimethylaminuria. The collaboration project began in 2021 after the diagnosis of several pediatric cases at the Sant Joan de Déu hospital.

“Developing the fragrance was not easy. We had to look for fragrances whose raw materials somehow interacted with that smell to block that receptor, as is the case with mandarin, to then give way to the pleasant notes of the fragrance,” explains Magdalena Rey, perfumer at Eurofragance. Based on that technical foundation, they ended up creating three products (a cologne water, a lotion, and a body oil).

The expert advises not to mix these products with other perfumes, as they may interfere with their effectiveness. “The shower gel has little influence because it is rinsed off with water and barely remains on the skin, so it is enough to use a mild and lightly scented one,” recommends Rey. TMAU patients can obtain these products free of charge and only have to cover the shipping costs.  

A study, conducted with a total of 20 volunteers, concluded that the almost complete neutralizing effect of the smell was obtained by using the three products in 80% of the participants. Rosa has tried the fragrances, although without a “satisfactory” result in her case.

Living with trimethylaminuria has forced Juan to give up activities as ordinary as going to the movies, attending indoor concerts, flying, or going to conferences. Rosa, for her part, has stopped attending classes and other activities because, she explains, “I couldn’t integrate,” and she has also had to greatly limit physical exercise. The disease has conditioned her way of “being in the world.” Even so, she has learned to “try not to define my identity solely through the disease, but to maintain other parts of me that go beyond this condition.”

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