Fish Odor Syndrome

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Fish Odor Syndrome

One of the most common topics women ask me to address relates to problems with various types of body odor.  While many of these can be easily traced to diet, infections, or even personal hygiene habits, there is a rare possibility that the cause of severe body odor problems can be hereditary, even if no family members have ever had this problem.  There is a very rare genetic condition called trimethylaminuria or “Fish Odor Syndrome,” which causes severe body odor.  This condition is so rare that most physicians are unaware of it, leaving frustrated patients without advice or solutions.

This condition is a recessive inborn error of metabolism.  This means that people who inherit one gene for it from each parent can be affected.  The genetic defect involves an enzyme that breaks down trimethylamine, a by-product of protein digestion released by bacteria living in the intestines. This molecule is the compound that gives fish their fishy odor; it has been described as smelling “foul” or “garbage-like” at low concentrations and “fishy” in larger amounts.

Trimethylaminuria can appear at any age, often depending upon the patient’s diet.  It is exacerbated by choline, which is found in eggs, liver and other organ meats, legumes, and some grains.  It can also be exacerbated by eating foods such as salt water fish, which contain trimethylamine-oxide.  The good news is that symptoms can often be reduced by following a low-protein diet that restricts foods containing choline or trimethylamine-oxide.  Some people also report that limiting lecithin (a common food additive that is also naturally found in eggs, soybeans, and corn) also helps reduce their body odor.  In some patients, avoiding dark green leafy vegetables and broccoli may help as well.  Because the odor is produced by the normal bacteria of the gut, low-dose antibiotics may also help reduce the odor-producing load.

Patients with this condition report foul odors in their breath, sweat, and urine.  The body odor is most commonly described as smelling like “rotting fish” and is most prominent in areas of active sweating (armpits or feet) and in the urine.  Affected patients may also complain of bad breath or a “horrible” taste in their mouths.  This condition may become more severe after puberty and the level of symptoms can vary.  The odor can result in severe social consequences and frustration which has led to aggressive behavior, poor school performance, and even severe depression. Suicidal thoughts are not uncommon in these patients. 

A variety of reports say that trimethylaminuria is worse in women than in men.  In women this condition can get worse around puberty, just before and during menstrual periods, after taking oral contraceptives, and around the time of menopause.  Some researchers suggest that this condition may be exacerbated by female hormones.  The condition may also develop without any genetic link in patients who have had liver or kidney disease. 

The diagnosis is usually missed due to an extreme lack of awareness.  When the diagnosis is made it is usually made clinically, but confirmed by complicated testing of the urine for elevated trimethylamine levels.