Intolerance (medicine)

Classification according to ICD-10
T78.9	Undesired side effect, unspecified
ICD-10 online (WHO version 2019)

An intolerance ( Latin intolerantia , from tolerāre , “to endure”, “to endure” with the negative prefix in- ) is in medicine a causally different group of metabolic disorders that arise due to insufficient processing of added or released substances. Often an enzyme defect or deficiency is the cause.

Since an allergy , a pseudo-allergy or an intolerance can cause similar symptoms, these terms are undifferentiated in common parlance and are often incorrectly used synonymously. As long as the diagnosis is not confirmed, it would be more correct to use the neutral terms intolerance, hypersensitivity reaction or undesirable side effect.

Intolerance manifests itself as symptoms of poisoning when a certain substance is administered in normal doses or when there is a normal concentration of a certain substance in the body. The immune system (as opposed to a real allergy ) or mediators such as histamine (as opposed to a pseudoallergy ) are by definition not involved. As pathological mechanisms in addition to apply enzymopathies also Komplementaktivierungen , excessively unstable cell membranes of mast cells and basophils , or metabolic disorders of arachidonic acid .

examples are

• the food intolerances like
  • lactose intolerance in the case of lactose intolerance and
• the clinically important analgesic intolerance ;
• the histamine intolerance
• the anaphylactoid reaction is a term that depicts the pathomechanism of intolerance. It can be as severe as allergic anaphylactic shock , but in contrast to this it has no previous sensitization phase and often occurs when drugs such as analgesics , anesthetics or X-ray contrast media are administered . ("Often" in relation to all cases of anaphylactoid reactions; as an undesirable side effect, however, they only make up a very small part of all analgesic and anesthetic side effects.)
• The celiac / celiac sprue is usually also subsumed under the intolerances, although here autoantibodies of the immune system create only the basis harmless for the malfunction of digestion itself gluten proteins from food.

If an intolerance is caused by an incorrectly or insufficiently formed enzyme , one also speaks of idiosyncrasy or idiosyncratic enzymopathy (e.g. in the case of lactose intolerance).

Individual evidence

1. ^ ^{A b} Roche Lexicon Medicine, 5th edition (online version), under the keywordIntoleranz .
2. ↑ ^{a b} Pschyrembel Clinical Dictionary Version 2002 (electronic version of the 258th edition), under the heading Intoleranz.
3. ↑ Pschyrembel Clinical Dictionary Version 2002 (electronic version of the 258th edition), under the heading Reaktion, anaphylaktoide.
4. ^ Roche Lexicon Medicine, 5th edition (online version), under the keyword idiosyncrasy .