Food intolerance

This is adverse reactions to food that are not immune-mediated and result from a wide range of mechanisms. Contaminants in food, preservatives and lactase deficiency may all be involved.

Lactose intolerance

Lactose intolerence may be as a result of lactase deficiency secondary to a disease process, such as coeliac disease or Crohn's disease. It may also result from decreased time of exposure to the intestinal mucosa, such as in short bowel syndrome or dumping syndrome.

Human milk contains around 200mmol/l of lactose, which is normally digested to glucose and galactose by the brush border enzyme lactase prior to absorption. In most people lactase deficiency is completely asymptomatic. However, some complain of colicky pain, abdominal distension, increased flatus and diarrhoea after ingesting milk or milk products. Irritable bowel syndrome is often suspected but the diagnosis is suggested by clinical improvement on lactose withdrawal. The lactose hydrogen breath test is a useful non-invasive confirmatory test.

Patients with lactose intolerance should avoid milk and milk products, including cheeses and butters. Some sufferers are able to tolerate small amounts of milk without symptoms.

Food allergies

Food allergies are immune-mediated disorders due to antibodies and hypersensitivity reactions. Up to 20% of the population perceive themselves to suffer from food allergy but only 1-2% of adults have genuine food allergies (Heaney 2000). The most common culprits are peanuts, milk, eggs and shellfish.

Clinical manifestations occur immediately on exposure and range from trivial to life-threatening or even fatal anaphylaxis. Allergic gastroenteropathy has features similar to eosinophilic gastroenteritis, while gastrointestinal anaphylaxis consists of nausea, vomiting, diarrhoea and sometimes cardiovascular and respiratory collapse. Fatal reactions to trace amounts of peanuts are well documented.

The diagnosis of food allergy is difficult to prove or refute. Skin prick tests and measurements of antigen-specific IgE antibodies in serum have limited predictive value.

Treatment of proven food allergy consists of detailed patient education and awareness, strict elimination of the offending antigen and in some cases antihistamines. Anaphylaxis should be treated as a medical emergency with resuscitation, airway support and intravenous adrenaline. Subsequently patients should wear an information bracelet and be taught to carry and use a preloaded adrenaline syringe.

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