With summer fully underway many people will notice that they are sweating more than usual.
A certain amount of sweat is a normal reaction to temperature and movement.
However, others might sweat even more due to conditions such as diabetes and an overactive thyroid.
In some cases though, the odour of your sweat could be more extreme.
According to the NHS, trimethylaminuria is an "uncommon" condition that causes an "unpleasant" rotting fish smell in bodily fluids including sweat.
"Trimethylaminuria symptoms can be present from birth, but they may not start until later in life, often around puberty," the health body explains.
"The only symptom is an unpleasant smell, typically of rotting fish - although it can be described as smelling like other things."
It can affect:
The odour may be "constant" or may "come and go", the NHS warns.
Trimethylamine is a strong-smelling chemical produced in the gut when bacteria breaks down food.
In most people the body is able to turn trimethylamine into a different chemical that doesn't smell.
However, in a person with trimethylaminuria the body is unable to do this and the chemical builds up in the body and seeps into fluids such as sweat.
This means trimethylamine builds up in the body and gets into bodily fluids like sweat.
In most cases of trimethylaminuria the sufferer inherits the condition, if both parents carry the FMO3 gene.
The NHS advises seeing your GP if you notice a "strong, unpleasant smell that doesn't go away".
Initially they will check for more common causes of the smell such as gum disease, body odour, bacterial vaginosis or a urinary tract infection.
They can check for more common causes, such as body odour, gum disease, a urinary tract infection or bacterial vaginosis.
If you suspect it could be trimethylaminuria it is worth telling your GP as "they may not have heard of it".
You may need to be referred to a specialist to run tests for the condition.
Although there is no cure, a doctor might prescribe antibiotics or recommend certain supplements that can help with the smell.
The NHS recommends avoiding the following foods for the same reason:
It also says avoiding strenuous exercise, finding ways to relax and frequently washing clothes can help.