If you child has redness that is similar to sun burn and your nappies stink like stale urine, it is likely it is caused by ammonia.
Ammonia will cause redness, ammonia burn, discomfort and pain to your child if nappies contain it. It will also degrade nappy fabrics such as bamboo, hemp, cotton.
How to identify ammonia
Ammonia (NH3) smells sharp, like a cat litter box or hair dye. An indicator of a developing ammonia problem would be nappies that smell like the boys toilets at high school. It has a high pH of 11 (on a scale of 0-14). The lead up to ammonia is subtle, and sometimes unnoticeable.
What does ammonia look like?
Ammonia is colourless, but if your nappies are stained and smell, that is an indication that they are not getting clean.
What causes ammonia?
The pH of a healthy humans urine ranges from of 6.5 to 8.0, i.e. it is neither acidic nor alkaline. Urine is nitrogen rich as it contains urea CO(NH2)2. Once urine leaves the body, the enzyme urease, which is found in a variety of bacteria, catalyses urea into ammonia.
The pH of the environment becomes alkaline because ammonia is alkaline.
Several species of bacteria belonging to the human microbial gut (enteric bacteria), which are abundant in poo  such as Klebsiella spp. and Proteus spp produce active urease which catalyses the formation of ammonia from urea.
Ammonia is a result of the nappies not being washed properly, see the How to prevent it? section below which outlines preventative methods.
What does it result in?
With repeat exposure ammonia is highly irritating to skin, it will cause nappy rash, redness in the nappy area/burns on skin, which looks like sunburn. It doesn’t go away within a short period of time.
Ammonia is also corrosive to fabrics, the more ammonia that forms, the more it degrades fabric.
Night nappies will show signs of ammonia before day nappies, because they hold a greater volume of urine.
How to get rid of it?
For serious ammonia, you can do a concentrated bleach soak on inserts only.
Benzalkonium Chloride (ie. Canesten Laundry Rinse) is ineffective at oxidising ammonia. Don’t use this sanitisation method to remove ammonia.
How to treat ammonia burn?
Use a rash cream such as Sudocream or Bepanthen on the affected areas. A microfleece liner and nappy free time will also help.
How does bleach oxidise ammonia?
Bleach (sodium hypochlorite) sanitises via the chlorination and chloramination process.
How to prevent ammonia?
The most important factor in preventing it, is removing soiling sufficiently and quickly. See our Wash Guidelines.
- Use a detergent that has sufficient strength to remove soiling.
- Use a dry pail with air flow.
- Do a separate night nappy rinse, especially if you have a top loader.
- Remove soiling within 24hrs by doing a daily pre wash with detergent; especially if extended dry pailing where main wash is done beyond day two, or if living in hot/humid climates, or if the nappies are used on older children eg toddlers.
- Wash in hot water (60 degrees).
- Ensure you do a pre wash and main wash cycle.
- Make sure your cycle length is long enough for main.
- Ensure that the main wash does not have excess suds.
- Diego Mora and Stefania Arioli, Microbial Urease in Health and Disease <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4263730/>.