Ammonia and cloth nappies

Ammonia is a colourless chemical that forms from urine within hours. It forms quicker in hot and humid environments. Mild ammonia smells like an unflushed toilet. Strong ammonia smells like hair dye or a dirty cat litter box. 

When the urine is not washed out of cloth nappies properly, or quickly enough, it turns into ammonia. This irritates babies’ sensitive skin and causes redness, rashes, discomfort and pain.

Even low levels of ammonia deteriorate fabrics such as cotton, bamboo or hemp. This deterioration starts as small holes that increase in size over time with wear and laundering. It does not degrade synthetic fabrics. 

Ammonia is an inevitable process of urine degradation and will occur even with the best wash routine. It is important to reduce ammonia with regular, best-practice washing. This prevents harm to your baby’s skin and slows damage to natural fibre inserts.

Identifying ammonia

The easiest way to identify ammonia is by smell. The smell of mild ammonia is like a stagnant toilet that hasn’t been flushed all day. Mild ammonia is unpleasant but can be subtle and unnoticeable depending on an individual’s sensitivity to smell. Strong ammonia smells like a dirty cat litter or hair dye. 

An inadequate wash routine will cause ammonia to develop. Signs of unclean cloth nappies:

• Nappies smell after first wash
• Nappies regularly come out of the wash with marks that look like gray shadows 
• Poo remaining in nappy elastics or on fabric after washing
• Nappies smell strongly of urine as soon as baby wees
• Baby’s room smells strongly of urine in the morning after wearing night nappy
• Unwashed nappies regularly smell strongly before first wash

Development of ammonia over time from urine

Ammonia and fabric degradation

Ammonia damages cellulose-based fabrics (plant-based fabrics such as bamboo, hemp and cotton). Fabric damage occurs after repetitive exposure over time rather than as a one-off situation. The more frequently an item is exposed to ammonia, the faster it will degrade. Ammonia won’t degrade synthetic fabrics. 

Over time fabric thins and develops holes as a result of use and repeated washing. Exposure to ammonia degrades fabrics prematurely. Ammonia damage shows up as holes on your cloth nappies. This damage is beyond regular wear and tear that is to be expected from repeated use and washes.

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

Ammonia rashes

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

Ammonia rashes are different to other redness and rashes, such as irritation from contact with poo, friction rashes or from sitting in a wet nappy too long.

Treating redness and rash

Use a high-quality rash cream such as Sudocrem 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.

If your baby has an ammonia rash you need to sanitise the nappies to remove (oxidise) the ammonia. If you have recurring ammonia follow our washing recommendations to improve your washing routine. 

Avoiding ammonia 

A daily first wash with detergent reduces the likelihood of ammonia. We recommend washing in warm-hot (40-60ºC) water with detergent in each wash. 

Keep dirty nappies as dry as possible before washing them. This allows water to evaporate and reduces one of the reactants (water) required for ammonia formation. Store dirty nappies in a plastic basket or open bucket. Avoid cramming soiled nappies, pull them apart and let them sit loosely or drape them over the side of the basket or bucket prior to washing. 

If storing nappies in a wet bag or closed container try to wash them at the end of each day. 

Using chlorine bleach in a daily first wash, with detergent, is the most effective way to remove any ammonia that formed before washing.

Removing ammonia from cloth nappies

If your nappies have ammonia you can successfully remove it using high heat or chlorine bleach.

Our chlorine bleach sanitise calculator has a range of chlorine bleach concentrations that are effective at oxidising mild, moderate and extreme ammonia. We have concentrations for PUL covers and inserts. Our instructions step through the process and note which concentrations are suitable for which fabrics.

Benzalkonium chloride products (for example, Canesten Laundry Rinse) will not oxidise ammonia. 

The myth of acidic urine

Previous theories about the cause of smells, burns and fabric damage were attributed to acidic urine (acidic wee). This thinking was especially prevalent in the early-mid 2010s when Clean Cloth Nappies formed. Although acidic urine can occur, it is very rare, it is a medical condition and requires a medical diagnosis. 

If your nappies smell, or your baby has persistent rashes or redness in their nappy areas, the most likely cause is ammonia from an insufficient wash routine. 

Ammonia is a strong alkaline and has a pH of 11-12. Alkalinity causes as much redness, discomfort and rashes as acidity.