Lactose Intolerance vs. Milk Allergy: in Babies, Toddlers & Kids

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Is it lactose intolerance or a milk allergy causing discomfort in your child? While both can affect your child’s reaction to dairy, they are not the same. Lactose intolerance is an enzyme deficiency impacting digestion, manifesting as bloating or diarrhea. In contrast, milk allergy triggers the immune system and can cause serious allergic reactions. This article breaks down lactose intolerance vs milk allergy, clarifying how you can recognize and manage these conditions in babies and toddlers.


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Key Takeaways

  • Lactose intolerance and milk allergy are distinct, with lactose intolerance resulting from an enzyme deficiency leading to digestive issues, and milk allergy involving an immune reaction to milk proteins that can cause severe allergic responses including anaphylaxis.

  • Diagnosis for lactose intolerance often includes hydrogen breath tests or lactose tolerance tests, whereas milk allergy diagnosis is typically conducted through skin-prick tests or measurement of IgE antibodies in the blood.

  • Management of lactose intolerance involves dietary adjustments to reduce lactose intake and may include lactase supplements, while milk allergy requires complete avoidance of dairy products and careful monitoring for hidden dairy ingredients.

Understanding lactose intolerance, milk allergies in baby, toddlers and kids

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Characterized by an inability to fully digest lactose, a sugar found in milk and dairy products, lactose intolerance arises due to a deficiency of the enzyme lactase. This should not be confused with a milk allergy, which involves the immune system identifying milk proteins as threats and reacting accordingly. A clear distinction between the two is critical as their management and dietary modifications differ significantly.

While lactose intolerance is a digestive problem, milk allergy is an immune system issue, and milk protein intolerance is another condition that affects some individuals. Approximately 36% of the US population struggles with lactose intolerance, and while less common, many babies and children react when they consume cow’s milk or formula made from it.

Causes of Lactose Intolerance

Lactose intolerance primarily stems from a deficiency in the lactase enzyme, necessary for digesting lactose found in consumed dairy products. This deficiency hinders the processing of dairy foods and can trigger symptoms like:

  • bloating

  • stomach discomfort

  • diarrhea

  • gas

This deficiency can result from both genetic and non-genetic factors, leading to the inability to digest lactose.

Lactose intolerance can manifest at any age, but it often becomes more noticeable in adulthood. In contrast, infants rarely experience lactose intolerance unless they are born with a rare condition known as congenital lactase deficiency. Some babies and young children may develop temporary lactose intolerance following a tummy bug or another condition that damages their gut lining.

Symptoms of Lactose Intolerance

For those with lactose intolerance, consuming dairy can lead to uncomfortable digestive symptoms. Common symptoms include bloating, diarrhea, and gas. These symptoms can appear within 30 minutes to 2 hours after consuming lactose-containing foods and can range from mild to severe, depending on the amount of lactose consumed and the individual’s tolerance level.

Many people with lactose intolerance can tolerate smaller servings of dairy, especially when consumed with other foods. Hard cheeses like Swiss or cheddar, which have a lower lactose content, are less likely to cause symptoms of lactose intolerance. However, if symptoms persist, doctors may suggest an elimination diet, which involves cutting out lactose intolerance and dairy from the diet and observing if symptoms improve.

Understanding Milk Allergy

In contrast, a milk allergy is an adverse immune response to milk proteins. The immune system mistakenly identifies these proteins as threats, triggering an allergic response that can potentially lead to a severe reaction known as anaphylaxis, which is life-threatening.

To prevent allergic reactions, individuals with a milk allergy must entirely eliminate milk and milk-containing products from their diet. This includes being diligent about reading food labels and asking about ingredients when eating out to ensure that no milk products are included.

Causes of Milk Allergy

A cow’s milk allergy is triggered when the immune system overreacts to proteins specifically found in cow’s milk. It’s not the lactose, or milk sugar, causing the issue but the proteins in the milk that the immune system incorrectly identifies as harmful.

This allergic response is the body’s defense mechanism against perceived threats. In the case of a milk allergy, the body treats the milk proteins as foreign invaders and mounts an attack, resulting in a range of symptoms from mild to severe.

Symptoms of Milk Allergy

The symptoms of a milk allergy, also known as milk allergy symptoms, can starkly contrast those of lactose intolerance. Common symptoms of milk allergy include hives and wheezing, quite a departure from the digestive symptoms seen in lactose intolerance.

However, milk allergy can trigger anaphylaxis, a severe allergic reaction that includes symptoms such as airway blockage and breathing difficulties. This can be life-threatening and requires immediate medical attention. Milk ranks as the third most common food to cause anaphylaxis, following peanuts and tree nuts. This underscores the significance of being aware of potential milk allergies.

Key Differences Between Lactose Intolerance and Milk Allergy

lactose intolerant girl
While both lactose intolerance and milk allergy can lead to discomfort after consuming milk, the key difference lies in their causes, age of onset, and the severity of reactions. As we’ve discussed, lactose intolerance is due to a deficiency of lactase, an enzyme required to digest lactose, while milk allergy involves an immune response to proteins in milk.


The severity of reactions also varies between the two conditions. Milk allergy can lead to severe allergic reactions, including life-threatening anaphylaxis, while lactose intolerance symptoms are generally limited to gastrointestinal discomfort.

Age of Onset

Another notable difference between lactose intolerance and milk allergy is the age at which they typically appear. Milk allergy most commonly appears during the first year of life, and many children outgrow it by age 3 to 5.

Lactose intolerance, on the other hand, can manifest at any point but often develops later in life, becoming more noticeable in adulthood. It’s rare in babies and usually only starts showing up after age three in children who were born full-term.

Severity of Reactions

The severity of reactions seen in lactose intolerance and milk allergy is another key point of distinction. While lactose intolerance can cause significant discomfort, it does not trigger severe, life-threatening reactions like anaphylaxis.

Milk allergy, on the other hand, can induce severe and potentially life-threatening reactions, including anaphylaxis. Milk ranks as the third most common food to cause anaphylaxis, surpassed only by peanuts and tree nuts. This highlights the importance of being aware of potential milk allergies and other food allergies, including the broader issue of food allergy awareness.

Diagnosis and Testing

When it comes to diagnosing lactose intolerance or milk allergy, a doctor assesses suspected cases by reviewing symptoms and the patient’s response to dietary modifications before conducting specific tests. These tests are designed to help confirm the diagnosis, differentiate between the two conditions, and guide the best course of treatment.


Notably, the diagnostic tests for lactose intolerance and milk allergy differ, mirroring the unique nature of these conditions. We will now delve into these tests.

Tests for Lactose Intolerance

For suspected cases of lactose intolerance, doctors may use specific tests like the hydrogen breath test and the lactose tolerance test, which measure lactose digestion. The hydrogen breath test involves consuming a lactose-rich liquid and then breathing into a container to measure the level of hydrogen in the breath.

In the lactose tolerance test, blood samples are taken after the patient consumes a lactose-rich liquid. An insufficient rise in blood glucose levels suggests that lactose was not adequately digested. These tests help confirm lactose intolerance and guide dietary modifications to manage symptoms.

Tests for Milk Allergy

When it comes to diagnosing milk allergy, skin-prick tests and blood sample testing are commonly used. In a skin-prick test, a small amount of the milk protein is pricked into the skin, and if a raised bump or hive develops, it indicates an allergic reaction to the protein.

Blood sample testing, on the other hand, measures specific IgE antibodies in the blood that react to milk proteins. Both these tests are crucial in confirming the presence of milk allergy and can help differentiate it from other conditions such as lactose intolerance.

Managing Your Child's Diet

Once a diagnosis of lactose intolerance or milk allergy is confirmed, it becomes vital to manage your child’s diet. Dietary modifications can help alleviate symptoms and prevent allergic reactions, while ensuring your child still receives all the necessary nutrients for healthy growth and development.


Depending on the condition, these dietary modifications can vary. For lactose intolerance, this might involve limiting lactose intake, while for milk allergy, it necessitates avoiding all dairy products entirely.

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Dietary Modifications for Lactose Intolerance

For individuals with lactose intolerance, dietary modifications can alleviate symptoms and improve quality of life. This may involve limiting their lactose intake, opting for dairy products with reduced lactose, and adjusting their overall diet accordingly.

Lactase enzyme supplements can also help individuals digest lactose more effectively, reducing the discomfort associated with lactose intolerance. Additionally, integrating lactose-free or lactose-reduced products into the diet is an effective way to manage lactose intolerance while still enjoying dairy products.

Dietary Modifications for Milk Allergy

For individuals with a milk allergy, strict avoidance of all dairy products is the most effective way to prevent allergic reactions, including dairy allergies. This means reading food labels carefully to ensure that products do not contain any dairy ingredients and contacting manufacturers when in doubt. It is crucial not to consume milk or any other dairy products to stay safe.

Hidden sources of cow’s milk in processed foods may include ingredients in baked goods and processed meats, which individuals with milk allergy need to avoid. Moreover, individuals with milk allergy need to find alternative sources of calcium and other nutrients to compensate for the exclusion of dairy from their diets.

Alternative Sources of Calcium and Vitamin D

Ensuring your child receives enough calcium and vitamin D, nutrients commonly obtained from dairy products, remains vital irrespective of whether they have lactose intolerance or a milk allergy. Fortunately, there are many non-dairy foods high in calcium and vitamin D.

Non-dairy foods high in calcium include broccoli, oranges, almonds, spinach, kale, okra, collards, soybeans, and white beans. Fish like sardines, salmon, perch, and rainbow trout also provide dietary calcium. As for vitamin D, it can be found in eggs, liver, and yogurt, and is also produced by the body through sun exposure. Foods fortified with vitamin D, such as some dairy alternatives, orange juice, soy milk, and cereals, along with fatty fish like tuna, mackerel, and salmon, can help meet vitamin D requirements.

Coping with Lactose Intolerance and Milk Allergy

Although living with lactose intolerance or a milk allergy can present challenges, it’s important to bear in mind that these conditions can be managed effectively with the right approach. One of the key strategies involves educating friends and family about the condition, which can facilitate supportive and inclusive meal planning during social gatherings.

In addition, bringing a lactose-free dish to social events ensures there’s a safe food option available. Eating a small meal or snack before attending events can also help prevent discomfort and allow for participation even when dairy-free options are limited.

Moreover, noting allergies or dietary restrictions on online booking platforms aids in smooth communication and preparation for the dining experience.


In conclusion, understanding the difference between lactose intolerance and milk allergy is crucial, especially when it comes to managing your child’s diet and ensuring their well-being. While both conditions can cause discomfort after consuming dairy, the cause, age of onset, and severity of reactions vary significantly. With the right dietary modifications, alternative sources of essential nutrients, and practical coping strategies, both conditions can be effectively managed. Remember, your knowledge and proactive approach can make a significant difference in your child’s health and happiness.

Frequently Asked Questions

What is the key difference between lactose intolerance and milk allergy?

The key difference is that lactose intolerance is caused by a deficiency of lactase, while a milk allergy involves an immune system reaction to milk proteins. So, the root cause of each condition is distinct.

Can lactose intolerance and milk allergy cause severe, life-threatening reactions?

Yes, milk allergy can lead to severe, life-threatening reactions such as anaphylaxis, while lactose intolerance does not cause such severe reactions.

At what age do lactose intolerance and milk allergy typically appear?

Lactose intolerance can manifest at any point but often develops later in life, while milk allergy most commonly appears during the first year of life.

How are lactose intolerance and milk allergy diagnosed?

Lactose intolerance is diagnosed using tests like the hydrogen breath test and the lactose tolerance test, while milk allergy is diagnosed through skin-prick tests and blood sample testing. Both conditions are diagnosed through specific tests tailored to each condition.

How can you manage lactose intolerance and milk allergy in your child's diet?

To manage lactose intolerance and milk allergy in your child's diet, limit lactose intake, use lactase enzyme supplements, and avoid all dairy products while carefully reading food labels for milk allergy.


This article was reviewed by Kayla Bridges, DCN, MS, RD-AP. Kayla Bridges is Director of Medical & Scientific Affairs at Else Nutrition, North America.


The content and advice provided in this article is for informational purposes only and is not a substitute for medical diagnosis, treatment, advice for specific medical conditions. Always consult a pediatrician to understand the individual needs of your child. The article expresses the views of the brand editor.

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