Ammonia and cloth nappies

Ammonia is formed from urea within hours. If ammonia is not washed out of cloth nappies properly or quickly enough it starts to degrade cellulose-based fabrics (for example, bamboo, hemp and cotton). Ammonia in cloth nappies causes skin irritation, redness and rash.

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. Mild ammonia is similar to a toilet that hasn’t been flushed all day. Mild ammonia is unpleasant but sometimes subtle and unnoticeable.

What does ammonia look like?

Ammonia is colourless. You can not see it. 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.

How ammonia is formed

Ammonia is formed from urea. The pH of a healthy human’s urine ranges from of 6.5 to 8.0 (neither acidic nor alkaline). Urine is nitrogen-rich as it contains urea CO(NH2)2. Once urine leaves the body, the enzyme urease, 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 burns

Ammonia is very irritating to skin. It causes nappy rash, general redness, and in extreme cases burns that look like sunburn.

Ammonia rashes are different to other 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 rash on infant, rash covers entire nappy area
Ammonia rash covering entire nappy area
Rash along elastics line

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 does not resolve the problem overnight or within a day or two, visit your doctor or child health nurse for a medical assessment.

Ammonia and fabric degradation

Ammonia damages cellulose-based fabrics (plant-based origins such as bamboo, hemp and cotton). Fabric damage occurs after repetitive exposure to ammonia, it occurs over weeks rather than as a one-off situation. The more frequently an item is exposed to ammonia, the faster it will degrade.

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 remove ammonia from cloth nappies

Our sanitise methods have a range of chlorine bleach concentrations that are effective at oxidising mild, moderate and extreme ammonia.

Benzalkonium chloride products (for example, Canesten Laundry Rinse) are ineffective at oxidising ammonia. Do not use benzalkonium chloride products to remove ammonia.

How does bleach oxidise ammonia?

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

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

How to prevent ammonia

The most important factor in preventing ammonia is removing soiling sufficiently and quickly.

  • Use a detergent that has sufficient strength to remove soiling.
  • Use an open dry pail.
  • Take extra care of night nappies – either a 60+ minute prewash in hot (60°C) water or a handwash with detergent prior to prewash.
  • 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°C).
  • Run both a prewash and main wash cycle.
  • Make sure your cycle length is long enough for main.
  • Ensure that the main wash does not have excess suds

References and further reading

  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.