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Lactose Intolerance in Babies: Symptoms, Signs, and Causes

Written by Taylor Cossairt , medically checked by child nutritionist

Lactose intolerance is your child’s inability to process lactose, a type of sugar found in milk. The reason they can’t break down lactose is that they don’t have enough lactase. Lactase is an enzyme that processes lactose in the digestive system. When your baby ingests lactose, they can’t process it properly, and they express symptoms like:

  • Vomiting
  • Diarrhea
  • Gas
  • And more

Symptoms usually show up between 30 minutes and two hours after ingesting lactose. Lactose is found in most dairy products like:

  • Butter
  • Cheese
  • Cream
  • Custard
  • Milk
  • Whipped cream
  • And more

Note that lactose intolerance and milk allergies aren’t the same things. A milk allergy is an immune system response that attacks proteins found in cows’ milk (read more about CMPA and Milk Allergies in babies).

Lactose intolerance is a digestive system response. And it happens when the body can’t break down sugars found in milk.

Lactose intolerance is rare in newborns and young children. Usually, symptoms start showing around three years of age. However, symptoms can show up sooner — especially if your child was born prematurely. Either way, there are different types of lactose intolerance:

Lactase Non-Persistent (LPN or Hypolactasia)

  • There’s not enough lactase enzyme in the small intestine to break down lactose
  • Considered primary lactose intolerance because it’s genetic or present at birth
  • Babies can usually have breastmilk or formula with lactose
  • The most common type of lactose intolerance and symptoms usually present later in life

Congenital Lactase Deficiency (Alactasia)

Secondary Lactose Intolerance

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Did you know? Up to 70% of the population has primary lactose intolerance. But not everyone who is lactose intolerant shows symptoms.

Lactose intolerance is often confused with galactosemia. It’s a rare, genetic disorder that inhibits the body’s ability to turn galactose into glucose. Galactose is a type of sugar and it can be found on its own, or alongside glucose to make lactose.

The biggest difference between galactosemia and lactose intolerance is severity. Galactosemia can be life-threatening. Lactose intolerance is uncomfortable, but it’s rarely if ever fatal.

Ready to learn more about lactose intolerance in babies?

Signs and Symptoms of Lactose Intolerance in Babies

Most babies experience symptoms within 30 minutes to two hours after ingesting lactose. This is because your baby’s body can’t process lactose as it moves through the digestive system. The most common symptoms of lactose intolerance in babies include:

Mild lactose intolerance

  • Nausea
  • Bloating
  • Gas
  • Loose and watery stools

Moderate lactose intolerance

  • Diarrhea
  • Vomiting
  • Abdominal cramps

Severe lactose intolerance

  • Sudden and severe stomach pain
  • Severe vomiting
  • Severe diarrhea

Many parents also notice excessive fussiness or sleeplessness. If your baby cries for several hours a day, several days a week, it could be a warning sign. This may indicate they’re experiencing pain related to CMPA (cow milk protein allergy).

It’s tough for parents and caregivers to know exactly how a child is feeling. This is because oftentimes, babies aren't talking yet. Or, they don’t have a strong enough vocabulary. Here are some ways your child may express discomfort because of lactose intolerance:

Non-Verbal Symptoms of Lactose Intolerance in Babies

  • Clenching their fists
  • Crying as they pass gas
  • Lifting or kicking their legs

When to call 911 for Lactose Intolerance

Lactose intolerance can be uncomfortable for your child, but it’s unlikely you’ll have to call 911. In most cases, lactose intolerance only impacts the digestive system. And symptoms should subside within 48 hours.

However, you should call 911 and seek medical attention immediately. This is especially true if your child is having an emergency or severe symptoms like:

  • Chronic abdominal pain
  • Low blood pressure
  • Loss of consciousness
  • Shortness of breath
  • Severe swelling of the mouth, throat, or face

If you notice any of the symptoms above, your child may have a food allergy. In some cases, food allergies can result in anaphylaxis which is potentially life-threatening. Don’t hesitate to call 911 in an emergency.

Top Foods to Avoid if your Baby is Lactose Intolerant

If your baby is lactose intolerant, there are a few ways to manage their symptoms. You can limit their intake of foods and drinks with lactose. Or, if they’re old enough, you can administer lactase. It's an enzyme that helps break down lactose in the digestive system.

As well, some parents or caregivers choose to switch to lactose-free formulas. This way formula is easier for a child to digest. When you switch your baby over to lactose-free formula, it can take up to two weeks to notice a difference.

Talk with your doctor about what’s safe for your child and their condition. In the meantime, here’s a list of the top foods your child can (and can’t) eat.

Foods to avoid if your baby is Lactose Intolerant:

  • Breaded or batter-dipped meat, fish, or poultry
  • Bread made with milk
  • Butter
  • Buttermilk
  • Butterscotch
  • Cheese spreads and cheese foods
  • Chowders
  • Cookies, cakes, and other desserts with milk
  • Cow’s milk
  • Cream
  • Cream cheese
  • Cream or cheese-filled pastries
  • Cream soups
  • Creamed vegetables
  • Custard
  • Evaporated or condensed milk
  • Frozen potato foods with milk or lactose
  • Fruit smoothies made with yogurt
  • Fruits or vegetables processed with lactose
  • Fudge, coated candies, and chocolates
  • Hot chocolate mixes
  • Ice cream
  • Instant mashed potato mixes
  • Kefir
  • Malted milk
  • Margarine with butter or milk
  • Meats in cream sauces
  • Most cheeses
  • Pancakes or waffles made with milk products
  • Party dips
  • Processed and natural cheeses
  • Processed meats with milk or lactose like hot dogs
  • Pudding
  • Reduced lactose milk
  • Sherbet
  • Soup mixes with milk products
  • Sour cream
  • Sweet acidophilus or lactobacillus milk
  • Vegetables coated in batter
  • Whey
  • Whipped cream
  • White sauces and gravies made with milk
  • Yogurt with or without live cultures

Foods your child can eat:

  • Angel food cake
  • Bread made without milk (Italian & French)
  • Broth
  • Canned nutrition drinks made with soy (and not milk)
  • Cereals made without milk
  • Cooked dried peas and beans
  • Cooked/baked fruits and vegetables made without milk products
  • Dairy-free frozen desserts made with rice or soy
  • Eggs cooked without milk
  • Fresh fruits & vegetables
  • Frozen pureed fruit bars
  • Fruit & vegetable juices
  • Gelatin desserts without milk or whipped cream
  • Gravies made with water
  • Honey
  • Jellies, jams, and preserves
  • Lactose-free milk
  • Margarine without butter or milk
  • Non-dairy creamers
  • Oils
  • Pasta, noodles, macaroni
  • Peanut butter, nuts, and seeds
  • Pies, cakes, other baked goods without milk
  • Plain herbs and spices
  • Potatoes, rice, and barley
  • Rice cakes without cheese topping
  • Rice milk drinks
  • Salad dressings made with milk
  • Saltines and whole-grain crackers
  • Shortenings
  • Sorbets
  • Soy cheeses
  • Soy-milks
  • Soybean and tofu products
  • Vegetable or meat soups without milk

Please note that the table above is a guideline and not a substitute for medical advice. Always check with your child’s doctor to find out what’s best for your baby and their age.

As well, don’t forget to check food labels for hidden lactose ingredients like:

Contains Lactose

  • Milk powder
  • Milk protein
  • Milk solids
  • Nonfat dry milk
  • Whey
  • Whey solids or whey protein

May Contain Lactose

  • Artificial flavoring
  • Caramel flavoring
  • Flavoring
  • High protein flour
  • Lactic acid
  • Natural flavoring
  • Rice cheese
  • Some non-dairy products
  • Soy cheese

How to Prevent and Treat Lactose Intolerance in Babies

Lactose is a type of sugar that’s usually a part of milk products. And it’s what your baby’s body can’t break down properly in the digestive tract if they’re lactose intolerant.

In most cases, lactose intolerance presenting in babies is rare and temporary. It’s usually caused by a viral illness or premature birth.

If your child genetically inherits lactose intolerance, symptoms usually appear later in life. This is because your baby is born with lactase in the digestive system. But they can’t produce any more of it. So as they age, they run out of the enzyme required to break down lactose.

Either way, the best way to manage their symptoms is to work with their doctor and develop a treatment plan. Some common prevention and treatment methods include:

Lactase enzyme supplement
  • Talk with your child’s doctor about a lactase enzyme supplement
  • It’s usually an over-the-counter (OTC) medication
  • Lactase is the enzyme that the body needs to break down lactose
Diet monitoring
  • For severe cases, consider removing lactose from your child’s diet
  • Work with a doctor to develop a diet that’s safe for your child
  • Supplement their diet with safe foods that are rich in vitamin D and calcium. Or administer vitamin D and calcium supplements
  • Check food labels for milk, lactose, and other similar ingredients. Food labels in the EU and UK should clearly identify common allergens (including milk). Look for allergens listed in bold, highlighted or underlined text
Dairy-free formulas
  • If your baby reacts to lactose in the formula, consider dairy-free or lactose-free formulas
  • Some alternative formulas are lactose-free and/or made with soy instead

Mothers who are breastfeeding

If you breastfeed a baby who is lactose intolerant, keep an eye on their symptoms and talk with your doctor. You may not have to switch from breastfeeding to formula-feeding. And in most cases, the amount of dairy you consume doesn’t impact the amount of lactose in your breastmilk.

Milk Allergies vs. CMPA vs. Lactose Intolerance in Babies

Milk allergies, CMPA, and lactose intolerance look a lot alike. And it’s hard for most parents and caregivers to tell the difference. Here’s a look at each one including its cause, symptoms, and treatments:

Milk Allergies (also known as cow milk protein allergy or CMPA)

Cause Symptoms Treatments
  • Allergic reaction to proteins found in cow’s milk
  • Immune system response
  • Hives
  • Rashes
  • Swelling of the mouth, throat, and face
  • Wheezing
  • OTC antihistamines
  • Prescription auto-injectors
  • Restrictive diet

Lactose Intolerance

Cause Symptoms Treatments
  • Missing lactase enzymes that break down lactose in the digestive system
  • Inability to process lactose, which is a sugar found in milk
  • Bloating
  • Gas
  • Stomach aches
  • Diarrhea
  • Vomiting
  • Lactase enzyme supplements
  • Restrictive diet

The best way to know for sure which condition your child has is to visit their pediatrician. Doctors and allergists have the tools to appropriately diagnose your baby.

Find out more about CMPA and Milk Allergies in babies here.

How to Diagnose Lactose Intolerance in Babies

There are a few ways doctors can test for lactose intolerance in children.

Hydrogen breath test

Stool test

Endoscopy

Food elimination diet

FAQ: Everything Parents and Caregivers need to Know about Lactose Intolerance in Babies

Can babies eat other dairy products if they’re lactose intolerant?

This depends on how severe your child’s intolerance to lactose is. For example, some babies have mild reactions. They can tolerate small amounts of lactose in moderation. But, other babies experience severe symptoms so it’s best to avoid dairy altogether.

Regardless, if your baby is lactose intolerant, they should avoid dairy products like:

  • Cheese
  • Ice cream
  • Milk
  • Yogurt

Use this list of ingredientsto get a better idea of what your baby should, and shouldn’t, eat.

Do babies outgrow lactose intolerance?

Is lactose intolerance genetic?

Can babies outgrow lactose intolerance?

Do newborns have lactose intolerance?

Does breastmilk contain lactose?

Should I avoid milk if I’m breastfeeding? What about formula feeding?