Ammonia and cloth nappies

Urine and ammonia go hand in hand, it is inevitable because ammonia is formed from urea within hours. If it isn’t washed out properly or quickly enough it starts to degrade cellulose based fabrics eg bamboo, hemp, cotton. The level of fabric degradation depends on the fabric.

When it isn’t washed out properly it causes skin irritation, redness and rash. Ammonia can’t be prevented, but it is possible to prevent skin irritation and damage to fabrics.

Graph showing how urea concentration declines and subsequent ammonia concentration increases over time
Urea concentration declines and subsequent ammonia concentration increases over time

How to identify ammonia

Ammonia formation is on a scale. Strong ammonia (NH3) smells sharp, like a cat litter box or hair dye, but mild ammonia is similar to a toilet that hasn’t been flushed all day. It is unpleasant but sometimes subtle and unnoticeable.

What does ammonia look like?

Ammonia is colourless, if your nappies are stained and smell, that is an indication that they are not getting clean, but even without stains and smells ammonia will develop. If the fabrics start developing holes the primary cause is likely to be ammonia damage.

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 [1] 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?

Ammonia is very irritating to skin, it will cause nappy rash, general redness, and in extreme cases burns which looks like sunburn. There are other reasons for redness and rash, such as teething, irritation from friction or wetness, because the nappy hasn’t been fitted correctly or has been left on too long.

Ammonia damages cellulose based fabrics (plant based origin eg bamboo, cotton etc), the more repeated ammonia that the fabric is exposed to, the more it degrades the fabric. Damage to fabrics happens as a result of repetitive exposure, meaning it occurs over weeks rather than a one off situation.

Bamboo inserts with signs of ammonia degradation
Bamboo inserts with signs of ammonia degradation

Night nappies will show signs of ammonia before day nappies, because they hold a greater volume of urine.

How to get rid of it?

Use one of our sanitise methods, the sanitise methods have a range of chlorine bleach concentrations which are effective at oxidising mild, moderate and extreme ammonia.

Benzalkonium Chloride (ie. Canesten Laundry Rinse) is ineffective at oxidising ammonia. Don’t use this sanitisation method to remove ammonia.

How to treat redness and rash?

Use a rash cream such as Sudocream or Bepanthen on the affected areas. A microfleece liner and nappy free time will also help. If a rash cream such as Sudocream or Bepanthen does not resolve the problem overnight or within a day or two, visit your Doctor for medical assessment.

How does bleach oxidise ammonia?

Bleach (sodium hypochlorite) sanitises via the chlorination and chloramination process.

The free chlorine (Cl-) produced sanitises
The chloroamination process sanintises, and oxidises ammonia

How to prevent ammonia?

The most important factor in preventing ammonia is removing soiling sufficiently and quickly. See our Wash Guidelines.

  • Use a detergent that has sufficient strength to remove soiling.
  • Use an open dry pail.
  • 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.


  1. Diego Mora and Stefania Arioli, Microbial Urease in Health and Disease <>.
  2. H Ray, D Saetta and T Boyer, Characterization of urea hydrolysis in fresh human urine and inhibition by chemical addition.