Breastfed Baby Poop Suddenly Smells Bad

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Breastfed Baby Poop Suddenly Smells Bad

It is not unusual that breastfed baby poop suddenly smells bad. That doesn’t mean anything and there’s no reason to be alarmed. Your baby’s first poop is called meconium, it is dark in color and can appear very strange for adults. Tomorrow or in a few days your baby will change the look, color, and smell of its poop. 

The smell of poop in babies who are breastfed by their mothers is almost non-existent. The poop is yellow in color and has a mustard density. Breast milk is the healthiest for the baby and all the nutrients are nicely broken down in the baby’s digestive tract. 

Breast milk passes quickly through the baby’s stomach, so there is almost no smell of baby poop. As the food remains in the intestines for a longer period of time, the more odor it produces. That’s why mothers who have babies that are bottle-fed, more frequently ask about the smell of their baby’s stool.

The problem can occur when a breastfed baby poop suddenly smells bad. The reason for this is when a breastfeeding mother eats some very spicy food or strong food. The baby gets all these spices through the milk into its stomach. In this situation, it’s normal that the baby will also have indigestion and gas, and there is a possibility that the poop will smell strange.

So breastfeeding mothers should take care of their diet and the problem is solved. Your baby’s stomach will react to what you eat, so you can track or record what you ate and how your baby reacted to certain types of food. 

It’s recommended to eat healthier and less spicy foods, not only because your baby will digest it easier, but also because the baby can learn to have a healthy diet in the future as well. This has been proven in many types of research, but parents should be aware that it is different for every baby.

A change in your baby’s odor can also be caused by a stomach virus. A baby can show well-known symptoms such as diarrhea, fever, and crying. There can also be changes in odor and amount of poop. This condition requires an absolute visit to the pediatrician.

Why does my breastfed baby poop smell so bad?

If your baby’s poop changes to smell, color and becomes more liquid, there may be problems with lactose intolerance or an allergy to some milk ingredients. Lactose intolerance is easily recognizable because the baby gets gas and bloating often along with fragrant stools. 

Lactose intolerance is the inability of the organism to process lactose. Milk and milk products are high in lactose. A digestive enzyme called lactase is not produced enough in the small intestine, resulting in lactose intolerance. This can definitely be the reason why breastfed baby poop suddenly smells bad.

It rarely occurs in newborns, but it can appear later in childhood as well. If it occurs in babies, as time passes, the organism develops and produces enough enzymes that break down dairy products. There is milk that your lactose intolerant baby can drink, but it is best to consult with your doctor who will tell you which type of milk is good for your baby.

Milk allergy occurs when the immune system reacts to a substance in milk. Symptoms are a change in the smell, usually reminding us of the smell of chemicals, changes in the color of poop, vomiting, and reddish swelling on the body and most often around the lips.

There are also severe symptoms that can occur like: anaphylactic shock, shortness of breath, and suffocation. Stop giving milk to babies, and be sure to seek medical advice immediately. 

Today, there are different types of adapted milk, plant milk, where proteins are broken down so that the body does not recognize it. Lactose has also been removed from milk, so babies with lactose intolerance and children who are allergic to milk can drink it.

Breastfed Baby Poop Suddenly Smells Bad

What causes foul-smelling stools in babies?

A foul smell of stool in your babies can also be caused by a stomach virus or bacteria. A baby can show well-known symptoms such as diarrhea, fever, abdominal pain with nausea.

At this point, the baby’s stool is pretty smelly, dark in color, and infrequent. This happens when microorganisms attack the baby’s intestinal mucosa. These intestinal infections most often attack babies and children, due to an underdeveloped immune system. 

They occur usually in the summer, and when the baby puts dirty fingers and dirty objects in its mouth. Dirty objects are often toys, bedding, and blankets. That is why it is necessary to maintain hygiene, and if the baby vomits when burping, the wet blanket should be washed so that microorganisms do not multiply. Toys should also be washed periodically to remove impurities. 

Due to all of the symptoms, babies can become dehydrated, so it is necessary to take them to the doctor immediately, where they will be provided with adequate medical care. The baby needs to be kept in a safe and clean environment that cannot hurt or endanger it.

Is breastfed baby poop supposed to stink?

No, breastfed baby poop is not supposed to stink. Breast milk is the best, healthiest, and easiest food for your baby. If you breastfeed your baby, it will progress quickly, and its stomach will not have problems with bloating and indigestion. 

The baby will be happy and cheerful and always ready to play with you. If you are breastfeeding your baby and the poop stinks, it means that the mother must take care of her diet. Do not eat strong and spicy food, because all these ingredients from food are transmitted to babies through milk. This is the reason why breastfed baby poop suddenly smells bad.

Eliminate fatty and spicy foods from your diet and your baby will not have problems with smelling stools anymore. It can happen that your baby greets you with a fart, which is a sign that her or his digestive tract is working well.

When should I worry about baby poop smell?

Breastfed Baby Poop Suddenly Smells Bad

You don’t need to worry when your baby’s stool smells, and that happens throughout the day. A baby stool can change the smell and appearance as well as the color from day to day. But if it lasts a long time it can mean some problems in the digestive tract. 

This can also mean that the milk or food you are giving to your baby does not suit it. In addition to the constant and persistent smell of the baby’s stool, you should also pay attention to the color. If your baby’s color is black, dark brown, red, or white, it can mean that your baby has serious health problems. Then it is necessary to immediately take the baby to a pediatrician who will provide her with adequate medical care.


Many parents are worried when they see that their baby’s poop has changed. This should be a completely normal thing once you start introducing your baby to solid food. Even the odor can be a bit unpleasant, but it’s totally normal at this point. 

However, it can happen to babies at the earliest stage. Even though there is less chance for an unpleasant odor for breastfed babies, it is not uncommon that breastfed baby poop suddenly smells bad. The reason for this is probably because the mother is eating something that is not soothing the baby’s digestive tract.

So, a breastfeeding woman should pay attention to what she eats because it can directly influence her child. It might be something strong and spicy that was causing digestive problems to your baby. Try to eat as healthy as possible because everything that the mother eats will go through the milk and in the end will reflect on the baby’s diet as well. 

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My name is Catherine. I'm a Mom and one of the avid writers working on HerScoop!