Are you lactose intolerant or not? Romanian studies show how it is confused with milk allergy or irritable bowel syndrome

In Romania, lactose intolerance is much less common than it is thought, while cow's milk protein allergy remains one of the most common food allergies in children.

A Romanian study, published in 2025 in the Journal of Gastrointestinal Liver Diseases, shows that many patients think they are lactose intolerant, but their perception is often wrong.

In an analysis that included 845 patients, only about 38% had actual intolerance confirmed by objective tests, although many more considered themselves intolerant. Self-perception proved imprecise: sensitivity was 67.8% (proportion of those who are truly lactose intolerant and think they have this problem), and specificity only 35.7% (how many of those who are not intolerant manage to recognize that they are not intolerant).

The conclusion of the study is that many people eliminate dairy without actually needing to.

Why does this confusion occur so often?

In practice, many of the symptoms attributed to lactose intolerance – bloating, abdominal cramps, gas, discomfort after meals – are non-specific and overlap with those of irritable bowel syndrome, an extremely common disorder in the population (approximately 10% of the Romanian population, according to doctors' estimates).

The Romanian study by specialists from Cluj points out that people tend to interpret any digestive symptom as “lactose intolerance”, although in reality, in the absence of objective tests such as the hydrogen breath test, it is difficult to establish the true cause. This is precisely why the authors of the study recommend that the lactose-free diet should not be adopted automatically, because unjustified restrictions can lead to nutritional deficits over time, especially calcium and vitamin D, with an impact on bone health.

Intolerance or allergy to milk?

While lactose intolerance is caused by an enzyme deficiency, cow's milk allergy involves a completely different mechanism. Allergy is a reaction of the immune system to milk proteins – casein and whey – and can cause various manifestations, from skin irritation to wheezing, vomiting or, in rare cases, anaphylaxis.

Unlike lactose intolerance, which only causes digestive discomfort, the allergy can be dangerous and requires strict avoidance of all products containing milk protein.

In the case of allergy, the body produces IgE antibodies against milk proteins and releases histamine with each exposure, which triggers the allergic reaction. In intolerance, it is not the immune system that reacts, but digestion is affected because lactose cannot be broken down efficiently. The differences are large, but often go unnoticed precisely because early symptoms may appear similar or because people rely on perceptions rather than medical assessment.

Cow's milk remains one of the most common causes of food allergies in young children, and reactions can sometimes appear minutes after consumption, sometimes hours later, which complicates diagnosis. Children may develop abdominal cramps, diarrhea, skin rashes or recurrent coughs, and in severe cases anaphylactic shock may occur, requiring immediate medical intervention. The good news is that many children outgrow this allergy as their digestive system matures, but correct diagnosis is essential to avoid risks.

In the case of lactose intolerance, things are different. The enzyme lactase, responsible for breaking down lactose, may be present in smaller amounts as we age, but most adults in Europe continue to produce it at levels sufficient to digest lactose without problems.

MYTH: “All adults become lactose intolerant over time”

One of the most common myths about lactase deficiency is that “all adults become lactose intolerant,” but genetic studies confirm that European populations have high rates of persistence of the enzyme that helps digest dairy. However, some people may experience transient digestive symptoms after consuming dairy for reasons unrelated to lactose – stress, fatty foods, irregular meals – and may mistakenly conclude that they are intolerant.

This is one of the most important conclusions of recent research: self-diagnosis is not reliable. The Romanian study shows that people correctly assess their intolerance only in a part of the cases, while a very large number eliminate dairy products from their diet unnecessarily.

In the absence of a complete medical evaluation, the risk is to overlap symptoms, to confuse intolerance with allergy or to avoid some of the most important sources of nutrients. That's why specialists recommend that any suspicion of intolerance be investigated with appropriate tests, and the difference between allergy and intolerance be very clearly understood: one is an immunological problem, the other a digestive one.

How to quickly tell the difference between milk allergy and lactose intolerance

Even though they can occur after eating the same foods, the two conditions manifest differently. Milk allergy most often has a rapid onset: redness of the skin, swelling of the lips, itching, wheezing or vomiting, which can occur within minutes or within hours.

However, some children develop delayed reactions, with persistent digestive symptoms, rashes, coughs or recurrent respiratory infections. There are also rare situations where exposure to milk leads to anaphylaxis, a severe reaction that must be treated with epinephrine.

In lactose intolerance, the symptoms are strictly digestive and appear a few hours after consumption, as the lactose reaches the colon and fermentation begins. There are no skin, respiratory or immunological symptoms, and the manifestations never progress to anaphylactic shock. This fundamental difference explains why lactose-free dairy products are tolerated by people with intolerance, but completely not recommended for those with a milk protein allergy.