From time to time I notice that during a run I really smell bad. I don't mean the normal sweaty smell, but very acrid and funky. It's almost an ammonia smell and it's extremely gross. I was worried that I am dying so I turned to google to help me out. This, by the way, is almost always a bad idea. It seems to me that any time you search symptoms on google you will end up coming away from the experience assured that you have cancer are are going to die. If you are a runner, or do a fair amount of cardio, then you may have stinky sweat like me. The reason is not cancer and you are not dying. The reason is simply that your body does not have enough carbohydrate energy and is breaking down amino acids for energy. The best explanation of why this happens is from a great article from www.bodybuilding.com. Here's an excerpt from the article:
The chemical make-up of ammonia is NH3. This means that there is one Nitrogen atom bound to three Hydrogen atoms. Ammonia can be a weak acid or a weak base, depending on what type of chemical it is suspended in. Ammonia has a strong, pungent odor that is easily recognizable in cleaning products, cat urine, and, for some people, sweat! The key to ammonia in urine and sweat is the nitrogen. The only macronutrient in your body that contains nitrogen is amino acids, the building blocks of protein. In fact, many bodybuilders are always seeking a "positive nitrogen balance" meaning that less nitrogen leaves their body than enters their body. Since nitrogen is in every amino acid, and amino acids are the building blocks of muscle, someone in positive nitrogen balance is more than likely gaining muscle mass.Having stinky sweat does not mean that your protein intake isn't high enough. In fact, it may be the opposite! You may be getting plenty of protein but not enough carbohydrates. They key to avoiding the 'smell' is to eat enough carbs for your activity. If your body does not have sufficient carbohydrates it will break down amino acids (protein) and you will smell like cat pee. Don't smell like cat pee, eat more carbs!
Your body uses amino acids for energy every day. There is no way to avoid this. Your body constantly goes into catabolic (tissue breakdown) and anabolic (tissue building) phases. When you accumulate mass (lean or fat), your anabolic phases exceed your catabolic phases, but you still experience both phases. When your body uses an amino acid for energy, it must convert the amino acid to a useable form of energy.
It does this by stripping the nitrogen atom off of the molecule. The skeleton molecule that is left behind is then further converted into glucose and used as fuel. In order to get rid of the excess nitrogen, your body typically processes the nitrogen in your kidneys and forms urea, CO(NH2)2 - basically, a carbon dioxide molecule bound to nitrogen and hydrogen. Urea is then excreted in the urine. If your kidneys cannot handle the load of nitrogen, then the nitrogen will be excreted as ammonia in your sweat.
One other factor to consider is water intake. The methods used for getting rid of excess ammonia, such as urine and sweat, all require water as a transport mechanism. If you are not getting adequate fluid, then the solution (ammonia + water) will not be diluted. Therefore, water plays a definite role. If you are not drinking enough fluids to have at least one or two clear urinations every day, you should drink more.
Based on this explanation, it is clear that your sweat will smell like ammonia only if an excessive amount of amino acids are being used for energy, or you are not receiving adequate water. This helps us find a solution to the problem. (source)
Since I learned this I have made sure to eat some carbs before I go on run. It can be as simple as an eating an apple or a granola bar. The upside is that the carbohydrates will be used by your body to provide you with an energy kick. That means you will have more energy to run harder faster or longer. So if your sweat smells like a litter box just eat more carbs before you exercise.