Food Allergy: symptoms and diagnosis in Luxembourg

A food allergy is an immune reaction that mistakes a food protein — peanut, egg, milk, tree nuts, fish — for a threat, triggering a response that can appear within minutes. It differs sharply from a food intolerance, which is far more common and rarely dangerous. If symptoms keep appearing after meals, the first step is a GP or paediatrician, who can refer to an allergist for proper testing.

Allergy or intolerance: not the same thing at all

Many adults describe themselves as "allergic to lactose" when they are, in fact, intolerant. A true allergy involves the immune system: it produces antibodies against a food protein, so the next exposure triggers an immediate reaction, sometimes severe, occasionally life-threatening. An intolerance usually comes from an enzyme shortfall — lactose being the classic example — and causes uncomfortable digestive symptoms without putting life at risk.

This is not a minor distinction: it shapes the entire management plan. A true allergy calls for strict avoidance of the food and, often, a prescribed adrenaline auto-injector. An intolerance is usually managed by adjusting quantities rather than total avoidance. Only a medical work-up can tell the two apart — relying on gut feeling risks either needless restriction or, worse, underestimating a real danger.

Recognising an allergic reaction

Symptoms typically appear within minutes of eating, occasionally up to two hours later. Mild to moderate reactions can include:

• itching or tingling of the mouth, throat or lips;
• hives, red itchy patches, swelling of the face;
• digestive symptoms: stomach pain, vomiting, diarrhoea;
• in infants, an unusual rash or fussiness shortly after a feed or a meal.

These signs warrant a medical appointment even if they settle on their own, because a future exposure could trigger something more serious.

Anaphylaxis: the signs that mean calling 112, no hesitation

Some reactions escalate within minutes and involve several organ systems at once — this is anaphylaxis, a life-threatening emergency. Watch for swelling of the throat or tongue, a hoarse voice, difficulty breathing or wheezing, a drop in blood pressure with dizziness, paleness, a racing pulse, or loss of consciousness. Faced with any of these signs — alone or combined with the hives and digestive symptoms already present — never wait to "see if it passes": call 112 straight away. If the person carries a prescribed adrenaline auto-injector for a known allergy, use it without delay, even before help arrives; adrenaline works fast, and a delay in giving it is the main factor behind severe outcomes in poorly managed anaphylaxis.

How allergists confirm the diagnosis

Diagnosis is never based on a hunch about a meal; it follows a structured process. The GP or paediatrician first takes a detailed history — the food, the timing, the symptoms, the circumstances — before referring to an allergist if a true allergy is suspected. The allergist relies on skin prick tests, blood tests for specific antibodies, and sometimes a supervised oral food challenge carried out under medical care, the only test that truly confirms an allergy with certainty. This work-up avoids two opposite mistakes: unnecessary food avoidance, which risks nutritional gaps and needless restriction, especially in children, and underestimating a genuine risk.

Living with a food allergy day to day

Once diagnosed, the challenge becomes largely organisational. Reading labels systematically is the first habit to build: EU rules require the fourteen major allergens to be clearly listed on any pre-packaged food, including possible traces from manufacturing. At school or nursery, an individual care plan helps arrange meals, trains staff in emergency steps, and ensures the emergency treatment is always within reach. At restaurants and while travelling, mentioning the allergy before ordering remains the most effective habit. Living with a food allergy does not mean living in constant fear: a clear action plan, shared with family, school and doctor, allows for a normal social life.

Introducing food to babies: what has changed

Guidance has shifted in recent years. For a long time, parents were told to delay introducing allergenic foods; current evidence shows the opposite — introducing them early and gradually, generally between four and six months, as part of complementary feeding, tends to reduce the risk of developing an allergy rather than increase it, including for peanut and egg. Each new food should be introduced one at a time, in small amounts, watching the baby over the following hours. If there is a family history of allergy or the infant has severe eczema, the paediatrician can offer tailored support for this step. Allergy consultations are covered by the Caisse nationale de santé under the usual rules; details are on cns.lu.