The myth of acidic urine

During the early to mid-2010s, Australian cloth nappy washing advice was very different than it is today. Many manufacturers cautioned people to only use small amounts of sensitive detergent. The result was cloth nappies that were not cleaned properly. They had pungent smells and caused chemical burns on babies’ bottoms. These smells and burns were often attributed to acidic urine (acidic wee). In reality, it was caused by ammonia that formed in the poorly cleaned nappy.

We liked to think the world of acidic wee is behind us. However, when we Googled ‘acidic wee’, ‘acidic urine’ and ‘teething wee’ in early 2025, we found this myth is still pervasive online. We won’t link to pages directly (Google’s AI summary feature might make it look like our advice!) Instead, we have collected screen grabs in this folder.

What is acidic urine?

The pH scale runs from 1 to 14, with 1 being the most acidic and 14 the most alkaline. Urine is usually 5.5-7.5. Although the optimal range is 6-7.5 it is still considered normal and no cause for concern if it falls between 4.5-8.0. This means that by nature, almost all urine is slightly acidic. 

It is very unusual that a healthy individual will have urine below 4.5. If you suspect your child has acidic urine, consult with a qualified medical professional.

What is normal?

Healthy and normal-coloured urine is straw or champagne coloured although there can be slight variations of this, especially based on what is being consumed. Beetroot, asparagus and rhubarb can all change the smell and colour of your urine but these changes are temporary and will return to normal within 24 hours.

Fresh urine should have a mild smell. Once urine comes in contact with air, ammonia begins to be produced. This means the longer urine sits exposed to oxygen, the stronger it smells.

Night time urine

Urine concentration varies throughout the day based on your hydration, exercise and fluid intake levels. The exception to this rule is urine produced overnight.

Your urine is generally the strongest smelling and darkest coloured when you have your first wee of the morning. This is because overnight, you produce something called vasopressin which is also known as Anti-Diuretic Hormone (ADH). This is a hormone that slows down your urine production so you don’t need to get up to the toilet often overnight. This means your urine is more concentrated and therefore, more acidic during this time.

As night nappies contain more concentrated urine, we recommend you wash them daily to slow ammonia production down.

Children start producing vasopressin at different ages but it is generally considered developmentally appropriate for them to reach sufficient levels of vasopressin to remain dry overnight between the ages of 3-8 years old. Some children reach this milestone sooner than others and some take longer. If you have concerns regarding your child’s night dryness, seek medical advice from a qualified professional.

Sanitising your nappies

If nappies smell strongly of urine or ammonia, or you notice raised red burns on your child’s bottom, sanitise the nappies.