4 Symptoms And Causes Of Lactose Intolerance In Babies

Digestive problems and failure to gain the required weight for age can be caused by an inability to digest milk sugars.

Written by Rohit Garoo Experience: 9 years
Last Updated on

While breastfeeding a newborn, if you notice that they are unable to contain the mother’s milk and develop nausea or diarrhea, it could be due to a condition called lactose intolerance in babies. Your infant may begin showing the symptoms of this condition from the very first feed or after a few days. Lactose intolerance may be a cause of concern in newborns since they become devoid of the sole nutrition, breastmilk. Read on as we share all details of lactose intolerance in infants and present you with useful tips that may help keep your infant nourished along with coping with the condition.

What Is Lactose  Intolerance In Babies?

Lactose intolerance, also called milk intolerance or hypolactasia, is a condition where a baby is unable to digest lactose, a type of sugar found in the milk of all mammals. The intolerance occurs due to small intestine’s inability to produce sufficient levels of the enzyme called lactase.

Lactase breaks down lactose into simpler molecules that are easier for the body to absorb. An insufficiency or absence of lactase prevents the breakdown of lactose, thus leading to lactose intolerance (1).

Lactose intolerance can be primary, secondary, or congenital, caused due to different reasons.

What Causes Lactose Intolerance In Babies?

Each type of lactose intolerance has different reasons behind it.

1. Primary lactose intolerance

It is also called primary hypolactasia and is the most common form of lactose intolerance in humans (2). The condition happens when the body produces lactase for the early years of life, but then slowly reduces and ceases the production as the infant grows. The only reason for it is the absence of lactase persistence genes. Since the genes for long-term lactase production are missing, the baby’s small intestine gradually loses the ability to make lactase. As the infant grows, lactase production could completely stop, and the baby would become lactose intolerant entirely.

Primary lactose intolerance usually occurs after the age of five years (3). Some studies even found people developing primary hypolactasia after 20 years (4). The timing of the presentation is genetically dependent on the ethnicity of the patients. 

So most parents realize their baby has this condition only after the child reaches five years. Since there is an adequate production of lactase during infancy, the baby can safely consume breast milk and other milk-based products in their early years.

2. Secondary lactose intolerance

Secondary lactose intolerance, also called secondary hypolactasia, is a more complicated condition. Here the infant is lactase persistent, which means they can digest lactose till adulthood.

However, due to damage to the internal mucosal lining of the small intestine, there is a sudden onset of lactose intolerance. The damage happens due to several conditions, with the key ones being (5):

  • Gastroenteritis
  • Irritable bowel syndrome (IBS)
  • Inflammatory bowel disease (IBD)
  • Tumors and cancers

Chemotherapy, which is a treatment for cancer, and grave illnesses like AIDS can cause lactose intolerance. Gastroenteritis usually induces temporary lactose intolerance in babies, a condition that is called transient lactose intolerance (6). The temporary condition lasts as long as the child has gastroenteritis. A lactose diet can be introduced once the child’s health comes back to normalcy.

3. Congenital lactose intolerance

It is also called congenital alactasia and is extremely rare. The body cannot produce lactase at all, which prevents the digestion of milk right from birth.

Congenital lactose intolerance occurs when the newborn is missing the genes for lactose secretion. It is an autosomal recessive condition and is associated with abnormalities in calcium metabolism as well. It can lead to hypercalcemia and nephrocalcinosis (a kidney disorder).

Lactose intolerance eventually causes a lifelong intolerance towards all types of milk, including breast milk (7).

4. Developmental lactose deficiency

This is a lactose malabsorption that is the result of prematurity. The production of lactase only picks up towards the end of pregnancy and babies born before 32 weeks gestation might have a problem with lactose absorption.

Are Lactose Tolerance And Milk Allergy The Same?

No. Lactose intolerance is an inability to digest lactose because the small intestines do not produce any or enough lactase. Lactose intolerance is an inability of the body to digest the carbohydrate called lactose. Milk allergy is an allergic reaction of the body against one of the proteins of milk.

Milk allergy is the immune system’s hyperactive response towards milk proteins, which leads to food allergy symptoms like acute vomiting after ingestion, skin rashes, swelling of the face, etc. (8). The immune system does not contribute to lactase deficiency, and lactose intolerance is not a type of food allergy.

Lactose overload in infants happens when the mother produces excess lactose-rich foremilk than fat-rich hindmilk. This condition is called hyperlactation and causes the baby to ingest more lactose than they can (9). It slows the digestion of the milk, causing tummy pain and discomfort for the baby. However, it is not lactose intolerance, and the baby’s small intestines eventually digest the lactose-rich milk.

Learning about the symptoms of lactose intolerance helps you differentiate between the condition and milk allergy or lactose overload.

What Are The Symptoms Of Lactose Intolerance?

These symptoms of lactose intolerance in babies manifest 30 to 120 minutes (two hours) after consumption of any milk, including breast milk, milk-based formula, and even cow’s milk (10):

  1. Abdominal pain and cramps: The infant will curl legs or rub the belly indicating that they are feeling uncomfortable around that part. The little one may repeatedly cry due to pain.
  2. Bloating and flatulence: The baby’s belly will appear bloated, and the little one will pass gas frequently. The tummy would be stiff due to the trapped air, and the infant may squeal even when you press the belly gently.
  3. Watery diarrhea: The stools get thin, and result in watery diarrhea. The stool could have a pungent smell due to its high acidity caused by undigested lactose.
  4. Nausea and vomiting: Vomiting follows nausea, and the baby feels sick all the time.

Rush to the doctor when you see these symptoms since they can quickly become severe. A medical diagnosis will ascertain if the baby has lactose intolerance.

How Is Lactose Intolerance In Infants Diagnosed?

The doctor will look for the physical symptoms of the condition and proceed to test if the baby has lactose intolerance.

A stool test is an ideal lactose intolerance test for infants. A stool sample is collected, and its acidity (pH level) is analyzed. If the stool is highly acidic, then it indicates the presence of undigested lactose. Since lactose is a type of glucose, stool tests also check for surplus glucose.

There are other lactose intolerance tests as well, but for adults. These tests can exacerbate the symptoms of lactose intolerance in infants since they require deliberate consumption of lactose.

For instance, the breath hydrogen level test measures the level of hydrogen in the breath. High hydrogen levels indicate undigested lactose in the body.

Another test is the blood test where glucose levels are measured. Both tests require prior consumption of a lactose-rich beverage after several hours of fasting, which is not recommended for infants. (11).

Some other ways to detect lactose intolerance are intestinal biopsy (collecting intestinal sample) and gene analysis (genetic sequencing). Intestinal biopsy is invasive and can be painful while genetic sequencing is expensive and has limited appeal.

A stool test, which is painless and easy, is thus widely used to diagnose lactose intolerance in infants.

A confirmed diagnosis is a step towards treating the condition and preventing the repeated bouts of symptoms.

How To Treat Lactose Intolerance In Babies?

There is no treatment for lactose intolerance in babies unless it is temporary. Temporary inability to digest lactose can be induced by bacterial gastroenteritis, which is curable through the use of antibiotics.

Primary lactose intolerance usually does not impact the infant since the lactase deficiency only begins after the age of five. A baby can thus get adequate nutrition from breast milk and other milk-based products.

Secondary and congenital lactose intolerance cannot be treated, and the baby has to live with the condition forever and has to avoid milk products for life (12) (13). There are no drugs to stimulate the production of lactase, although there are lactase enzyme supplements that can be used to treat mild lactose intolerance. These supplements can be added to milk products at least 30 minutes prior to consumption so that they start breaking the lactose down before ingestion.

So if there’s no treatment, can lactose intolerance be prevented?

How To Prevent Lactose Intolerance In Infants?

There is no way to prevent lactose intolerance as it is genetic, which cannot be cured or altered (14). Thankfully, the condition can be managed, and an infant can live a healthy life with some help.

How To Manage Lactose Intolerance In Babies?

You can feed the baby lactose-free food so that they get proper nourishment. However, the first food of a baby’s life is breast milk, which itself is rich in lactose.

Breastfeeding a lactose intolerant infant:

If the baby suffers from clinically-diagnosed primary lactose intolerance, then it is safe to breastfeed the baby. The baby’s small intestine will efficiently produce lactase, and he will have no trouble with breast milk.

In the case of temporary lactose intolerance, the mother can breastfeed the baby after the doctor confirms that the baby is lactose tolerant again.

Breastfeeding is a problem only if the baby has congenital and full-time secondary lactose intolerance. In such cases, you have to look at other sources of nourishment for the baby.

Foods for lactose intolerant babies:

Providing adequate nourishment to a lactose intolerant infant is the biggest predicament for parents. Milk is an excellent source of calcium and several micronutrients. The absence of milk in a baby’s diet leaves a vacuum that seems difficult to fill. Nevertheless, some nutritious foods can efficiently replenish and replace milk in a baby’s diet:

  1. Soy-based formula: It is made from the soy protein extracted from the soybean and is naturally free of lactose. It is an ideal replacement for breast milk and can also be used for older children.

This baby food is enriched with micronutrients and calcium for the healthy growth of the baby. The American Academy of Pediatrics recommends soy-based formula as a safe and cost-effective food for infants that suffer from lactose intolerance (15).

  1. Lactose-free milk and formula: Some formulas contain all the goodness of milk without the presence of lactose. The advancement of food technology has also enabled exclusion of lactose from milk while retaining its nutritional value.
  1. Vegetables: Vegetables such as spinach, broccoli, and green beans are an excellent source of calcium for babies older than six months (16).
  1. Meat and eggs: Eggs are rich in vitamins while meat is an excellent source of micronutrients essential for the body’s immunity. A weaning lactose intolerant baby can be fed a combination of meat and eggs. Meats are safe to introduce at six months, while eggs are after 12 months (17).

These foods provide the nutrients that a baby would have otherwise received from milk. Experts state that parents can also consider giving vitamin and calcium supplements to the lactose intolerant baby, but only after a discussion with the doctor (12). Focusing on milk replacements is important, and so is avoiding foods that are hidden sources of milk.

Foods to avoid by a lactose intolerant baby:

Some foods are an indirect source of lactose since they contain milk:

  • Milk bread: The milk powder in it contains lactose.
  • Processed baby food: Several ready-to-eat baby food products contain milk sugars, which is lactose.
  • Biscuits: It may contain milk powder.
  • Foods like pancakes and cakes: Older infants may be able to eat these, but if they are lactose intolerant, then they must avoid these foods since milk is one of the ingredients in them.

Babies with mild lactose intolerance could tolerate cultured dairy products such as yogurt and cheese. Smaller portions of milk may also have no adverse effect. However, it is best to consult a doctor before giving your baby anything with milk in it.

Frequently Asked Questions

1. How long does lactose intolerance last in babies?

The duration of lactose intolerance in babies depends on its type. Lactose intolerance from a viral disease is generally short-term and may go away with treatment. However, lactose intolerance can also be long-term (12).

2. Do lactose intolerant babies gain weight?

No, babies with lactose intolerance may have difficulty gaining weight, which is one of the symptoms of lactose intolerant babies (18).

3. Can breastfed babies be lactose intolerant?

Breastfed babies can also be lactose intolerant because breast milk contains lactose (18).

Lactose intolerance in babies is an uncommon condition but possible. Depending on the underlying cause, it can be of different types. Generally, babies with primary lactose intolerance can consume breast milk. However, those with congenital lactose intolerance can’t consume breast milk right from birth. Therefore, preventing lactose intolerance in babies is not possible. However, offering lactose-free milk and foods, such as soy-based formula, lactose-free milk and formula, cereal, veggies, meat, and eggs, is a great way to manage the condition and ensure your baby is well-nourished.


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  2. Margus Lember; ( 2012); Hypolactasia: a common enzyme deficiency leading to lactose malabsorption and intolerance.
  3. D Nagy et al., (2009); Prevalence of adult-type hypolactasia as diagnosed with genetic and lactose hydrogen breath tests in Hungarians.
  4. Leena Seppo et al., (2008); Can primary hypolactasia manifest itself after the age of 20 years? A two-decade follow-up study.
  5. Daniel L. Swagerty, Jr et al., (2002); Lactose Intolerance.
  6. R W Bartrop and D Hull; (1973); Transient lactose intolerance in infancy.
  7. Lena Diekmann et al; (2015); Congenital lactose intolerance is triggered by severe mutations on both alleles of the lactase gene.
  8. Adriano Henrique do Nascimento Rangel et al., (2016); Lactose intolerance and cow’s milk protein allergy.
  9. C. M. Smillie and Suzanne Hetzel Campbell; (2005); Hyperlactation – How left-brained ’rules’ for breastfeeding wreak havoc with a natural process.
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  11. Lactose tolerance tests.
  12. Lactose Intolerance in Infants & Children: Parent FAQs.
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  15. Jatinder Bhatia et al., (2008); Use of Soy Protein-Based Formulas in Infant Feeding.
  16. Expert Food Allergy Care.
  17. Feeding Your Baby: The First Year
  18. Lactose intolerance in babies
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Rohit Garoo is a writer-turned-editor with over 9 years of experience in content writing, editing, and content marketing. He did his bachelors in Science at St. Xavier's College, Hyderabad, and masters in Business Administration at Osmania University.

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