Here there is an immune reaction against proteins in food. Special antibodies are formed. The foods are eventually considered threatening by the immune system and trigger strong defensive responses, such as allergic inflammation of the oral mucosa, nausea, vomiting, diarrhoea. Rash, swelling, or respiratory symptoms (such as asthma) are also often observed. In extreme cases, even circulatory shock may develop. Food allergies in infancy and childhood differ from those in adulthood in that they are characteristically caused by different allergens. While children primarily react to cow’s milk, chicken eggs, wheat, nuts, and soy, food allergies in adulthood are usually linked to pollen allergy.

Much more common than allergies are “non-immunological” intolerance reactions to food. Examples of this would be:

Lactose intolerance

Deficiency or absence of the digestive enzyme lactase in the small intestine.
Symptoms: flatulence, nausea, diarrhoea
Diagnosis by means of a hydrogen breath test (no insurance coverage, not performed in our clinic).

Fructose malabsorption, colloquially “fructose intolerance"

Low number of glucose transporters in the small intestine.
Symptoms: intestinal cramps, flatulence, diarrhoea, feeling of fullness.
Diagnosis by means of a hydrogen breath test (no insurance coverage, not performed in our clinic).

Histamine intolerance

Reduced enzymatic degradation of histamine.
Symptoms: indigestion, headache, symptoms concerning the skin (details below).
Diagnosis: no reliable test available. Trial by determination of diamine oxidase (histaminase) or special skin test.

In principle, one must differentiate between local symptoms and systemic reactions:

In addition to the measures taken in the case of other allergies:

• Accurate recording of medical history
• Skin test
• Blood test for allergy antibodies of the IgE class

The following measures are useful for food allergies:

• Keep a food journal (food, drink, medications)
• Description of all occurring symptoms with time of occurrence
• Elimination diet: omitting all suspected foods > improvement?
• Re-introducing the suspected foods > recurrence of symptoms?
• Provocation test: deliberate intake of the suspected food under medical supervision
• Double-blind, placebo-controlled provocation: sometimes necessary to make a definite diagnosis. To clarify if an important part of the diet really causes disease and therefore cannot be eaten/drunk (for example, cows’ milk in children). Neither the doctor nor the patient knows whether it was provoked with the suspected material (capsule with dried milk) or with a placebo (for example, a capsule containing glucose). Symptoms of illness should only occur in case of provocation with the relevant allergy trigger. Such a fully objective system takes into account expectations, mental factors, etc.

The therapy of food allergies aims primarily at avoiding the triggering food (“elimination diet”). This is sometimes easily possible (example: allergy to asparagus, honey, seafood, etc.). In other cases, it is very difficult, as some substances are very common and may be hidden in food (e.g. cow’s milk, chicken eggs, wheat, soy, spices, etc.). If ever dramatic symptoms have occurred after eating food, it is necessary to take tablets, asthma inhalers, or even an auto-injector.

Histamine is a biologically active product of the decomposition of the amino acid histidine, which occurs naturally in proteins. The substance is stored in humans in special cells and released in inflammatory stimuli. As a mediator substance histamine produces swelling, redness, itching, and pain.

Histamine is also released as part of an allergic reaction, usually producing local allergic inflammation at the site of contact with the allergy trigger (e.g. runny nose, conjunctivitis, wheals on the skin, etc.). If histamine is released in large quantities and the histamine levels in the bloodstream rise, then also circulatory effects – from a drop in blood pressure, palpitations, to circulatory shock – are possible. Such reactions may, for example, occur in an allergy to insect venom or food allergies if the allergy trigger enters the bloodstream.

However, the biological processes leading to the production of histamine also occur outside of humans in nature, so histamine is produced, for example, in the context of fermentation processes.