A baby’s urine smells strong for many reasons. The common culprits are dehydration, diet changes, and urinary tract infections(UTI). Most of the time, smelly urine in babies is nothing serious and clears up with simple fixes like increasing fluids.
Sometimes, though, strong-smelling urine could signal danger. Being able to catch the difference between a harmless cause and a warning sign will keep your little one healthy.
In this article, we'll walk you through the main causes of smelly pee, what a healthy baby's urine should look like, and the urine colour changes that matter. We'll also explain why bed wetting urine smells so strong and when it's time to call your doctor.
Let's dive into it.
Baby's pee smells strong due to medical conditions like urinary tract infections or lifestyle factors like dehydration. Most causes are harmless and easy to fix at home. Let's start with the medical reasons, then cover lifestyle factors.
Around one-third of babies with foul-smelling urine have a urinary tract infection. UTIs aren't the only medical cause worth knowing about, though. Constipation, jaundice, kidney problems, and even diabetes can also change how your child's urine smells. When you spot these early, you can get the right treatment before things get worse.
A UTI happens when bacteria enter the urinary tract and cause a bacterial infection in the bladder. This infection doesn’t discriminate between genders, which is why you should watch for fever, cloudy urine, and unusual fussiness during nappy changes (and yes, those 3 am nappy changes do count as detective work).
What does constipation and leftover urine mean exactly? Well, hard stools press against the bladder and stop it from emptying fully. Because of this, leftover urine sits in the bladder and develops a foul odour over time. Increasing fibre and fluids usually gets things moving again.
When a newborn's liver isn't processing waste products properly, their urine turns dark yellow and smells stronger than usual. You might also notice yellowing of the skin and eyes alongside these changes. We recommend you keep an eye out for all of these signs.
Most cases clear up within two weeks, though severe jaundice needs medical attention.
A kidney infection can cause strong-smelling urine along with abdominal pain and fever. Your little one might also cry or arch their back during nappy changes if they're experiencing discomfort. When you notice these signs together, your child's healthcare provider should check for these health conditions.
Diabetes causes sweet-smelling urine because excess glucose spills into your baby's pee. If your newborn's urine smells like maple syrup or fruit, this could signal a serious illness (sounds weird, but it's a sign you need to be aware of). Contact your child's healthcare provider immediately rather than waiting to see if the smell fades.
When you understand these medical causes, you can act quickly and save your baby from those endless meltdowns.
With medical causes out of the way, let's look at lifestyle factors, which are far more common. These are usually easy to fix with simple changes at home. Dehydration, your diet when breastfeeding, and certain medications are the main lifestyle culprits behind smelly urine in babies.
When your baby isn't getting enough breast milk or formula, their urine becomes concentrated with more waste products. This means the urine produces a stronger odour than you'd normally notice. For instance, dark yellow pee is a clear sign your baby needs more fluids, especially during hot weather.
Through our practical experience with breastfeeding mothers, that certain foods, such as asparagus and garlic, are the most common causes of a change in pee smell. What you eat passes through breast milk to your baby, which then creates that familiar asparagus pee smell. Fortunately, this passes within a few hours after your meal.
Certain medications, like antibiotics, can change your baby's pee smell temporarily, and vitamins may cause a stronger odour too. If you're breastfeeding and taking medication, this can also affect your baby's urine since it passes through your milk (formula contains different metabolites that don't have this effect).
After you figure out the lifestyle cause, sorting it out at home is usually quick and easy.
A healthy baby's urine should be pale yellow to light yellow and nearly odourless. Any change from this gives you a clue that something is off. Here's what to look for with colour, feeding type, and solids.
Normally, baby urine is pale yellow with a mild or almost odourless scent. Along with colour, frequency is another good indicator of hydration. Your baby should have 5 or more wet diapers daily after the first week, which is a healthy sign that they're getting enough breast milk or formula.
As long as the urine colour stays light yellow and the pee smell is barely noticeable, your little one is likely well hydrated.
Are you doubting if your feeding method affects how your baby's pee smells? Yes, it does. Breastfed babies often have lighter, less smelly urine than formula-fed newborns because breast milk digests more easily than formula (formula contains different metabolites that affect urine composition).
Because of this, parents notice that formula-fed babies may have slightly darker yellow pee with a stronger odour. Rest assured, this is completely normal for their feeding type.
Now that your baby is 6 months and has started solids, their urine smell and colour will change. The reason for this is that new foods introduce different waste products into your child's urine, which creates stronger odours than you noticed before. This change is completely normal as your baby's digestion matures.
With healthy urine covered, here's what different colour changes can tell you about your baby boy or girl.
Urine colour changes show hydration levels and can signal health conditions needing attention. Most colour shifts come down to how much fluid your baby is getting, though some changes need a closer look. Here's a quick overview of what different colours mean:
| Urine colour | What It Means | Action Needed |
| Pale yellow | Well hydrated and healthy | None, keep up current feeding |
| Dark yellow or amber | Dehydration or concentrated urine | Increase breast milk or formula |
| Orange-red powder (brick dust) | Urate crystals (common in newborns) | Usually resolves once milk comes in |
| Pink tinted | Highly concentrated urine | Increase fluids, monitor for changes |
| Brown or tea-coloured | Severe dehydration or liver problems | See your GP promptly |
| Red or blood-tinged | Possible blood in urine | Seek medical attention right away |
Let's break down the most common colour changes in more detail.
Dark yellow baby pee means highly concentrated urine, which points to dehydration. This usually goes back to normal within a few hours when you increase feeds throughout the day. If the dark yellow pee continues despite extra fluids, check in with your child's healthcare provider.
Have you noticed an orange-red powder in your newborn's nappy? Believe it or not, that alarming colour isn't blood at all. This is called brick dust, and it's actually urate crystals that form when urine is highly concentrated.
You'll commonly see this in the first few days of life when you are still producing low-volume colostrum. Once your milk supply increases and your baby starts feeding more, the brick dust should disappear on its own.
Recognising abnormal urine odours and colours early helps you seek medical attention immediately. For example, brown baby pee may indicate severe dehydration or liver problems. On the other end of the spectrum, pink-tinted pee in newborns often means highly concentrated urine rather than blood (this one's non-negotiable, parents).
In both cases, contact your child's healthcare provider right away. Quick action with unusual colours gives your little one the best chance of a simple fix. Beyond colour, smell is another clue worth paying attention to.
Up next, we explain why bed wetting urine smells like ammonia.
Bed wetting urine gives off a foul odour like ammonia because it sits in fabric for hours overnight. As the urine breaks down, it releases ammonia gas. Frankly, the smell can be overwhelming when you walk into the room in the morning. If you're dealing with nocturnal enuresis, you've probably noticed it smells like cat pee, which is completely normal for overnight accidents.
No worries, though, by making simple changes, the smell can be reduced significantly. Based on our firsthand experience helping parents, waterproof mattress protectors work well for keeping odours contained, and washing bedding promptly prevents ammonia from setting into the fabric.
If the accidents continue or you notice other symptoms alongside the smell, speak with your child's healthcare provider.
See your child's healthcare provider when smelly urine comes with fever, pain, or other symptoms. Smelly pee as the only symptom is rarely a concern, but when it appears alongside warning signs, it's worth getting checked.
Below are the signs that need attention.
Is stinky pee the only symptom, or have you noticed fever or cloudy urine too? Here are the warning signs that need prompt evaluation:
If you spot any of the above symptoms together with smelly urine, don't wait to book an appointment.
Maple syrup urine disease (MSUD) is a rare metabolic disorder affecting how your baby's body processes certain amino acids. But wait, there's more to watch for beyond the sweet smell. Babies with MSUD often show a combination of signs in the first few days of life:
These metabolic disorders are rare, but early diagnosis makes a real difference in treatment outcomes.
If you're ever unsure whether your baby's pee smells strong enough to need attention, trust your instincts and call your GP.
Most causes of smelly urine in babies are harmless and easy to fix: dehydration, diet changes, and constipation. As we mentioned earlier, increasing fluids often solves these problems within a day or two. Even then, keeping an eye on urine colour and smell helps you catch issues early and avoid unnecessary worry.
That said, not every smell should be ignored. If smelly urine persists or comes with fever, pain, cloudy urine, or other symptoms, speak with your GP sooner rather than later. Early action gives your little one the best chance of a quick recovery.
And when you need products to help manage your child's incontinence, Ontex Healthcare has you covered with comfortable, reliable options for babies and children.
Disclaimer: This blog provides general health and product information for educational purposes only. It is not intended to diagnose, treat, or replace advice from your healthcare professional. Always seek guidance from your GP, nurse, continence advisor, or pharmacist regarding your individual needs. If symptoms persist or you’re unsure about product use, consult a qualified healthcare provider.
