Dairy products are foods produced from animal milk, most commonly from cows, while dairy alternatives are made from plant-based milk. Dairy products are a good source of nutrition. However, cow’s milk is the most common food allergen in infants and young children, and the allergy may persist into adulthood.

According to the American College of Allergy, Asthma & Immunology (ACAAI), roughly 2–3% of children under 3 years have a milk allergy. While many children are likely to outgrow the allergy in their youth, some evidence suggests that it may persist beyond 16 years in about 20% of people.

A dairy or milk allergy occurs when a person’s body experiences an immune reaction to the proteins present in milk. Their immune system recognizes the proteins as foreign, similar to a pathogen such as bacteria, triggering an immune response with symptoms ranging from mild to very severe.

While cow’s milk is the most common dairy allergen, people can also have an allergic response to other animal milk, such as goat, sheep, or buffalo. Plant-based milk, such as almond, soy, and rice, can also trigger an allergic reaction. Many people may confuse dairy allergies with lactose intolerance or a cow’s milk protein intolerance as they often share symptoms, but the three conditions are very different.

This article discusses the symptoms and causes of dairy allergies and how they differ from lactose intolerance.

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Dairy allergies usually appear within the first few months of life before 6 months, with allergic reactions that range from minor to severe and life threatening. Symptoms typically appear within a few minutes to hours after ingesting milk. While dairy allergies can refer to an allergy to any dairy product, they most often involve cow’s milk.

A person may experience various symptoms of true milk or dairy allergy. These include:

Sometimes, cow’s milk can cause anaphylaxis, a severe allergic reaction that is a medical emergency. Signs that a person is experiencing anaphylaxis can include:

The allergic symptoms people experience are due to how their body reacts to proteins present in the dairy product. For example, in cow’s milk, two main proteins called whey and casein can cause an allergic reaction in some people. These allergens trigger an immune-mediated response in the body as the immune system attempts to fight them.

In response to the dairy proteins, which the immune system identifies as an invader, the body overreacts and produces antibodies called immunoglobulin E (IgE). When activated by milk proteins, these antibodies release chemicals, such as histamines, that result in an allergic reaction.

Each type of IgE antibody is specific for each type of allergen. This is why some people may only be allergic to dairy products, as they only have the IgE antibodies specific to dairy. Other people may have allergic reactions to multiple allergens as they have more types of IgE antibodies.

Researchers do not fully understand why some substances trigger allergies and others do not. Multiple factors, such as a family history of allergies, likely play a role in developing allergic conditions.

Many people mistake dairy allergies with lactose intolerance because both require eliminating dairy from the diet and have overlapping symptoms. However, dairy allergy affects the immune system, while lactose intolerance is a problem with the digestive system.

Lactose intolerance is a digestive problem where a person lacks lactase, an enzyme that breaks down the sugar found in milk called lactose. This can cause symptoms such as bloating, gas, diarrhea, and abdominal pain.

People may also confuse a dairy allergy with cow’s milk protein intolerance (CMPI). However, CMPI symptoms typically take longer to manifest, while allergy symptoms usually appear within minutes to hours. Some people may also refer to it as food protein-induced enterocolitis syndrome (FPIES).

CMPI does not necessarily involve the immune system and may result in injury to the stomach and intestines. Unlike other reactions that can trigger a response throughout the body, FPIES normally affects the gastrointestinal system, causing symptoms such as blood in the stool, colic, diarrhea, and abdominal pain and cramps.

Certain factors may increase a person’s chance of developing milk allergy. These may include:

  • Age: Milk allergy is common in infants and children younger than 5 years old.
  • Presence of other allergies and atopic conditions: Children with milk allergy may develop other allergies and may also be at risk of atopic march, which involves developing other allergic conditions, such as eczema, allergic rhinitis, and asthma.
  • Family history: A 2018 study states milk allergy is three times higher in children whose parents have allergies.
  • Antibiotic exposure: A 2021 mouse study suggests that early exposure to antibiotics may increase the risk of food allergies.
  • Age when introducing complementary food: A 2020 study found that infants given food before 4 months are at a higher risk than those introduced to food beyond 6 months.

On the other hand, an extended breastfeeding period and having pets at home seem to be protective factors that may decrease a child’s risk for milk allergy.

There is no specific test to diagnose milk allergy. Doctors will primarily rely on physical examination, a detailed history of symptoms, and tests that can indicate an allergy, such as:

  • Skin prick test: An allergist will inject a small amount of milk protein into the skin. If this area swells or develops a welt within 15–20 minutes, it may indicate a milk allergy.
  • Blood test: This test checks for the presence of serum-specific IgE (sIgE) antibodies to help determine if a person may react to dairy proteins.
  • Oral food challenge: Experts refer to this as the gold standard for diagnosing food allergies. It involves a person eating small amounts of dairy products to see if a reaction occurs. Since this may carry a risk for anaphylaxis, a healthcare professional will perform this in the clinic.

As with other food allergies, the primary way to prevent a reaction is by strictly eliminating dairy from the diet. People may seek the help of a dietitian to plan nutritionally balanced meals and take supplements to replace nutrients found in milk, such as calcium, riboflavin, and vitamin D.

Milk is 1 of 8 major allergens that account for a majority of food allergies and serious allergic reactions in the United States. As such, people may want to use the following tips to avoid serious reactions:

  • Checking food labels: People must check ingredient labels to exclude food that contains milk and dairy. Milk-derived ingredients, such as artificial cheese and butter flavor, and whey and casein hydrolysates are common in processed foods. People should also avoid ingredients with the lac- prefix, such as lactitol, lactic acid, and sodium lactate.
  • Asking about food preparation: When ordering takeaways or dining out, it is essential to ask about the food preparation. Some people may cook the foods with milk or butter.
  • Using antihistamines: Over-the-counter antihistamines may help manage mild allergic reactions.
  • Carrying epinephrine: People with severe allergic reactions may require an epinephrine injection, also known as adrenaline. Therefore it is advisable for the person or a caregiver to carry epinephrine at all times in case of an emergency.

Parents who do not know whether their child has lactose intolerance or milk allergy should ask their doctors. They should consult with their doctors immediately if their child has symptoms of an allergic reaction, including itching, hives, and abdominal pain. Additionally, they should seek immediate treatment if a person presents with symptoms of anaphylaxis, such as:

  • difficulty breathing
  • hives all over the body
  • swelling of face, tongue, and throat

People with a dairy allergy diagnosis should speak with their doctors about preparing an action plan if severe allergic reactions occur. Doctors may also take this time to demonstrate how to use injectable epinephrine.

People who have an allergy to cow’s milk may also have an allergy to other animal milk, as well as plant-based milk. Typically, a doctor will advise what alternatives and what processes can make dairy products safe to consume.

For infants, a doctor may recommend breast milk. However, it is important that the caregiver also removes dairy from their diet while breastfeeding. They may also suggest hydrolyzed dairy products. These are items that undergo processes to remove the milk proteins. Alternatively, they may recommend substituting milk with water or juice.

Click here to learn more about dairy alternatives.

Milk and dairy allergies are the most common food allergy in children. They occur due to the immune system overreacting quickly to proteins present in dairy products. People may confuse dairy allergies with other conditions, such as lactose or cow’s milk protein intolerance, but the conditions are very different. Allergies involve the immune system, and symptoms occur within minutes to hours, ranging from mild to severe and life threatening.

There is currently no cure for dairy allergies, but many children may outgrow it. To avoid reactions, it is advisable for people to eliminate dairy from their diet. This may involve checking food labels, food preparation, and using dairy alternatives.