Bloating, stuffy nose or tummy ache? The child may have a food intolerance. What genetic tests can determine the exact cause

Stomach pain, bloating, skin rashes or stuffy nose after eating may seem like random reactions. In reality, they can hide different food intolerances with distinct mechanisms: lactose intolerance and histamine intolerance. Doctors explain the differences, when genetic testing is justified and what adjustments parents can make at home, without drastic diets.

Lactose and histamine are two different substances with completely distinct roles in the body, but which can become the source of unpleasant symptoms when not processed correctly. Lactose is a natural sugar present in milk and most dairy products. To be digested, it needs an enzyme called lactase, produced in the small intestine. When lactase is insufficient, lactose ends up undigested in the colon, where it is fermented by bacteria. The result is the appearance of classic digestive symptoms: bloating, gas, abdominal pain and sometimes diarrhea. Lactose intolerance is not an allergy and does not involve the immune system, but a purely digestive mechanism, related to the body's ability to produce lactase.

Histamine, on the other hand, is not a sugar, but a substance involved in multiple biological processes. It is a natural chemical mediator, produced by the body, with a role in the immune response, in the regulation of gastric secretion and in the functioning of the nervous system. In addition, histamine is also found in certain foods or is formed in fermented and processed foods. Normally, excess histamine is broken down by enzymes, especially diamine oxidase (DAO). When this mechanism does not work effectively, histamine accumulates and can generate various digestive and extraintestinal symptoms. It is this difference in mechanism that explains why lactose intolerance and histamine intolerance can be similar in onset, but develop differently.

Lactose intolerance vs. histamine intolerance: how to differentiate them by symptoms

For parents, the first warning sign is often digestive: the child complains of abdominal pain, is bloated or has soft stools. These symptoms can occur in both lactose intolerance and histamine intolerance, but the context in which they occur makes the difference. “The important difference is not necessarily how much it hurts, but in what context these symptoms appear and what other manifestations accompany them,” explains geneticist Anca Bârdan.

In lactose intolerance, the picture is predominantly digestive and closely related to dairy consumption. Problems occur after milk, yogurt, ice cream or other products containing lactose. The child has gas, bloating, abdominal pain and sometimes diarrhea. If the situation persists and dairy products are consumed constantly, stagnation or weight gain below expectations may also occur, precisely because digestive discomfort affects food intake. The pattern is usually repetitive and easy to spot: the same foods trigger the same symptoms.

In histamine intolerance, things are less obvious. The reactions are not related to a single food, but to a wide category: aged cheeses, cold meats, processed fish, but also tomatoes, strawberries, chocolate or highly processed foods. In addition to digestive symptoms, other manifestations occur, such as skin rashes, facial redness, itching, stuffy or runny nose after meals, headaches or migraines (migraine is one of the most common symptoms of diamine oxidase deficiency). Some parents also notice changes in behavior – irritability, restlessness or difficulty concentrating – especially after meals but also during periods of fatigue and stress. It is precisely this diversity of symptoms that makes histamine intolerance more difficult to recognize “at first”.

When does genetic testing make sense and what, specifically, does the result say?

Genetic testing is not an automatic first step, but one that is warranted when symptoms recur and form a pattern. “Genetic predisposition does not automatically mean disease, nor does it guarantee that a child will have clinical symptoms,” emphasizes geneticist Anca Bârdan.

In the case of histamine intolerance, genetic testing for the DAO enzyme is considered when the child has a suggestive picture: digestive reactions associated with rashes, redness, stuffy nose or headaches after eating foods rich in histamine. The indication becomes stronger if there are first-degree relatives with similar symptoms or with a confirmed diagnosis.

Genetic testing can show variants in genes involved in DAO synthesis or function, indicating a lower or higher predisposition. Important for parents: this result shows a risk, not an active intolerance.

For lactose intolerance, the genetic test for lactase shows how the child's body is “programmed” to produce this enzyme in the long term. It is especially useful when digestive symptoms constantly occur after dairy and there is a family history. As with histamine, the genetic test indicates a predisposition, it does not alone confirm clinical intolerance. Therefore, it is interpreted together with the symptoms and, if necessary, with other investigations, such as the breath test for lactose intolerance. This is the method most commonly used to diagnose lactose malabsorption.

What can be adjusted at home if there is a predisposition, without extreme diets

A genetic result confirming a predisposition does not automatically follow severe restrictions. Intervention begins with controlled adjustments and careful monitoring.

In practice, explains Anca Bârdan, it is recommended to “limit or exclude foods with demonstrated potential trigger”, for a period of observation, not the long-term elimination of whole food groups.

For suspected lactose intolerance, this may mean temporarily reducing classic dairy products and testing tolerance to lactose-free variants, carefully watching the child's reactions. In the case of histamine, one begins by avoiding foods known to be high in histamine, without making the diet excessively restrictive. In certain situations, the doctor may recommend supplements – for example, enzymes – but these are not used in isolation, but integrated into a medical plan.

An extremely useful tool for parents is the food diary. Daily notation of foods, symptoms and context (fatigue, infections, stress) helps identify real patterns and refine the diet. Based on this information, a personalized nutritional plan can be built, ideally with the support of a nutritionist, taking into account the child's age and growth needs.