A strong ammonia smell coming from your vagina is due to an overgrowth of certain ammonia-producing bacteria. Bacteria have various abilities to produce ammonia, with the pH of the environment largely dictating just how much is produced. Some bacteria produce more when the vagina is alkaline, which is what BV-causing bacteria tend to do.
In bacterial vaginosis (BV), teamwork between different bacterial species, and indeed the presence of some bacteria over others, can mean the odour is less fishy and more ammonic.
About ammonia in your vagina
Ammonia’s pH can change, but it is typically very alkaline, with the bottle of ammonia in the laundry cupboard having a pH of about 11 (blue in the diagram below). Remember that a healthy vagina is acidic, a pH of about 4, while water is neutral at a pH of 7.
Ammonia in the vagina, excreted by microbes, has an alkalising effect. This means the pH of the vagina goes up, past its healthy level, and into the danger zone of BV.
How is ammonia made in the vagina by microbes?
Ammonia is made all throughout your body in different systems and processes, playing a role in your urinary system, digestive system, and your vagina.
In the intestines, ammonia is made from the breakdown of proteins, which your liver then turns into urea, which is what you excrete in your urine. Microbes use ammonia as a source of nitrogen.
Most bacteria form less ammonia at the acidic pH of 5.0 compared to that produced at a more neutral pH of 7.0. When lactose was fermented, it represses the formation and release of ammonia.
Microbes that produce ammonia
Microbes that produce the most ammonia are typically gram-negative anaerobic species, clostridia, enterobacteria and Bacillus spp., while gram-positive, streptococci and micrococci produce modest amounts. Lactobacilli and yeast produce very little ammonia.
(This list is incomplete – we’re still working on this! Most bacteria use and/or produce ammonia, but we’re just establishing the ones that cause the odour in the vagina specifically)