dairy allergy

Dairy Allergy vs Lactose Intolerance

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Dairy Allergy vs. Lactose Intolerance: What’s the Difference?

The domestication of ruminants over 10,000 years ago led to the development of milk as an extremely nutrient-dense food;

Lactose intolerance and dairy allergies prevent everyone from enjoying the vast variety of dairy products.

They are frequently confused despite being different conditions, which could lead to unnecessary restrictions on diet.

In this article, we examine the main differences between lactose intolerance and dairy allergy.

What is lactose intolerance?

Those who suffer from lactose intolerance are unable to digest lactose in foods containing lactose, such as dairy.

An infant’s diet consists primarily of lactose, which is the primary carbohydrate in cow’s milk. However, child consumption of milk and dairy decreases with age, as does the enzymes needed to digest lactose.

In the small intestine, lactose needs to be digested and absorbed by the enzyme lactase to become glucose and galactose.

Lactose intolerance is the result of a deficiency of lactase at the brush border of the small intestine, which is also known as lactase deficiency.

Types of lactase deficiency

As a result of lactase deficiency, lactose intolerance can occur in four different ways.

Primary lactase deficiency: It’s genetically determined and occurs in 70-75% of the world’s adult population. Lactase non-persistence is the most common type. It begins at around the age of two, but symptoms may not appear until late adolescence or adulthood as lactase production declines sharply..

  • Secondary lactase deficiency: Allergies to food, infections, or diseases such as Chron’s and celiac disease can cause this condition. Treating the cause usually improves lactose tolerance.
  • Developmental lactase deficiency: This occurs in premature babies due to the development of lactase-producing cells in the small intestine after birth. It lasts a short period after they are born.
  • Congenital lactase deficiency: It is a very rare hereditary condition in which no lactase is produced in the small intestine from birth.

It can be seen that most adults are lactose intolerant after infancy, and only a minority have developed lactase persistence.

The majority of people suffering from lactose intolerance are able to tolerate some amount of lactose without experiencing any symptoms.

The amount of lactose found in one cup (240mL) of milk may be as much as 12 grams in a single dose. In spite of this, the amount varies considerably.

Because of this, lactose intolerance is primarily treated by reducing the amount of lactose in the diet rather than eliminating it completely.


Lactose intolerance occurs when the enzyme lactase is deficient, preventing the body from digesting milk’s primary carbohydrate.

What is a dairy allergy?

As well as food allergies, dairy allergies are also known as cow’s milk allergies. There are several causes of anaphylaxis caused by food allergies, including peanuts, tree nuts, and fish allergies.

Symptoms of immune-mediated reactions are associated with cow’s milk proteins. An immune response is launched when the body’s immune system reacts to a specific protein in milk.

As a result of exposure to the same protein repeatedly, the body releases immune mediators and responds again, resulting in the release of chemicals during cow’s milk allergy symptoms.

When children are young, they are usually prone to developing early childhood diseases, and they usually regress by the age of six.

A child who suffers from cow’s milk allergies is most likely to be allergic to casein and whey proteins.

In order to treat the condition, a diet devoid of cow’s milk is prescribed. Dairy products may also be avoided if you are nursing since cow’s milk protein is passed through breast milk.


During the first year of life, cow’s milk allergy often appears and then regresses after about six years of age.


There are several digestive and nondigestive symptoms associated with both lactose intolerance and cow’s milk allergy.

In spite of the fact that some symptoms are the same between the two, others are only characteristic of one or the other.

When undigested lactose is fermented by bacteria in the colon, it causes digestive symptoms that appear 30 to 2 hours after consumption.

Cow’s milk allergy, on the other hand, shows different symptoms depending on whether it is IgE or non-IgE mediated.

IgE-mediated symptoms: Within minutes after ingestion, rapid-onset symptoms typically include skin and respiratory symptoms, and in severe cases, anaphylaxis.

Non-IgE-mediated symptoms: These symptoms are predominantly delayed reactions affecting the skin and gastrointestinal tract.

Shared symptoms

There are various digestive symptoms shared by both conditions, which is most likely why they are confused. As an example, they include

  • diarrhea
  • nausea
  • abdominal pain

Lactose intolerance symptoms

Flatulence, constipation, borborygmus or a rumbling stomach, as well as bloating are some other digestive symptoms caused by lactose intolerance.

There are also nondigestive symptoms associated with lactose intolerance that can occur in up to 20% of people, including headache, vertigo, dizziness, memory loss, and loss of concentration, along with muscle and joint pain, mouth ulcers, and tiredness.

Cow’s milk allergy symptoms

Skin and respiratory systems are the most commonly affected by cow’s milk allergy symptoms.

Itchy lips, swelling of the tongue, throat, or lips, shortness of breath, and nausea are some of the most common symptoms.

Anaphylaxis may also be a complication of severe cases, a medical emergency that could be fatal if untreated, leading to the closure of your airways and a drop in blood pressure.


A cow’s milk allergy and lactose intolerance share some digestive symptoms, including nausea, abdominal pain, and diarrhea. It is important to note, however, that both conditions have symptoms that affect other parts of the body as well.

Risk factors

There are some risk factors that may increase the chances of developing lactose intolerance or allergies to cow’s milk.

Risk factors for lactose intolerance

Only a few people can digest lactose into their old age since most humans cease producing lactase with age.

A person’s ethnicity may have a bearing on the global distribution and the age at which lactase declines.

There are a number of countries in the world where lactose intolerance may be prevalent and onset may be very early.

South Americans, Africans, and Asians account for more than 50% of the world’s population

People in Asian countries make up up to 100% of the population

Between the ages of 2 and 3 years, children of African, Asian, or Hispanic descent may begin to exhibit symptoms

Symptoms usually appear between the ages of 5 and 6 and during adolescence in children of European and American descent

Northern European populations exhibit the lactase-persistence trait at a higher rate than southern Europeans.

Risk factors for cow’s milk allergy

It is common for cow’s milk allergy to disappear around age six, in contrast to lactose intolerance. Approximately 1–2% of children are affected by it, so it is largely limited to children. Despite this, studies show that male children who have other allergies, such as multiple food allergies, asthma, atopic dermatitis, and allergic rhinitis, are twice as likely to have cow’s milk allergies.

The ethnicity of a child may play a role as well, with evidence suggesting that non-Hispanic Black and non-Hispanic white children are more likely to develop cow’s milk allergies.


For lactose intolerance, ethnicity is the most important factor, while for cow’s milk allergy, multiple allergies among male children are the main risk factor.


The diagnostic tests for lactose intolerance and cow’s milk allergy are different, as they are two distinct conditions.

In order to diagnose lactose intolerance, the following tests are most commonly used:

Lactose breath test (LBT): The most common test for lactose intolerance is the hydrogen breath test, which measures the amount of hydrogen in the expiring air after consuming 20–50 grams of lactose after a fast of 8–12 hours. There is a positive correlation between hydrogen levels above 20 parts per million (ppm).

Lactose tolerance test: In terms of blood tests, this is the second most common. It measures the level of blood sugar following a lactose consumption. It indicates that the body is unable to digest and absorb lactose if blood sugar levels cannot rise above 1.1-1.4 mmol/L.

Genetic test: It is possible to identify genetic variations associated with lactase persistence or non-persistence through genetic testing. The high cost of this procedure prevents it from being performed frequently.

Intestinal biopsies: While highly effective, intestinal biopsies are not widely used because they are very expensive and invasive.

The primary diagnostic tests for cow’s milk allergy include:

Double-blind, placebo-controlled oral food challenge: Usually, a professional performs this test to determine if a person has food allergies by providing small amounts of the food and gradually increasing the amount until a reaction occurs.

Skin prick test: Tests are performed by pricking the skin with a lancet containing an allergen drop. A wheal that is bigger than the negative control is considered positive. It is important to contact an allergist/immunologist if there is any possibility of false positives.

Specific serum IgE: A blood test that measures the amount of IgE in your blood determines whether or not you will react to milk proteins. It measures the likelihood of a reaction in your blood, but it cannot be relied upon as a diagnosis by itself due to the high probability of false positives.


A variety of diagnostic methods are available for lactose intolerance and cow’s milk allergy, ranging from minimally invasive to highly invasive.

The bottom line

There is a difference between lactose intolerance and cow’s milk allergy caused by dairy consumption.

In contrast to lactose intolerance, cow’s milk allergy is an immune reaction to milk proteins, whereas lactose intolerance is caused by the inability to digest lactose.

There are several differences between lactose intolerance and cow’s milk allergy, even though there are symptoms such as nausea, diarrhea, and abdominal pain that may apply to both conditions.

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