Post-infectious lactose intolerance

Questions on Post-infectious lactose intolerance (PILI) answered:

Q. What is post-infectious lactose intolerance?

Post-infectious lactose intolerance (PILI) is a temporary loss of the ability to digest a sugar known as lactose, commonly found in milk-containing foods and drinks. PILI is a complication of common gastrointestinal infections in people who were able to digest dairy products before the start of the infection.

Q. What infections cause lactose intolerance?

The infections that have been linked to PILI are those viral, bacterial and parasitic infections that cause non-inflammatory diarrhoea i.e. infections the only cause minimal damage to the intestinal lining. These include rotavirus, Giardia intestinalis, Cryptosporidium and Cyclospora. Accurate figures are lacking, but PILI probably occurs in only a small proportion of all non-inflammatory infective diarrhoeas.

Q. Why does gastrointestinal infection cause lactose intolerance?

PILI is caused by temporary loss of the ability of the small intestine to digest dietary lactose when the lining of the small intestine becomes damaged by the infectious agent (viruses, bacteria or parasites). The temporary loss of intestinal digestive enzyme function leaves lactose intact. As a result it cannot be absorbed and stays in the intestine, keeping water with it. Bacteria normally present in the small intestine metabolise the excess lactose, producing hydrogen, methane and carbon dioxide gas. They also increase the acidity of intestinal contents. PILI is not an allergic reaction and should be distinguished from food allergies.

Q. What are its signs and symptoms?

Lactose intolerance means that consumption of milk and other lactose-containing dairy products will cause gas production, leading to abdominal discomfort, bloating, belching and flatulence. Stools may be noticeably bulky, loose and even diarrhoeal. Stool pH will be low and a hydrogen breath test, if available, may be positive.

Q. How long will it last?

Studies on rotavirus infection show that PILI lasts for an average of a few days if the gastroenteritis is mild, but may persist for much longer if there is prolonged gastroenteritis. Detailed figures are lacking for most specific infections, particularly in adults.

Q. What can be done about it?

PILI is normally a temporary condition and should improve with time even if nothing is done about it.

The options your physician can offer you include

  • waiting it out (mild lactose intolerance)
  • avoiding milk and other dairy products (butter, cream, ice cream, yoghurt, cheese and anything with whey products)
  • using lactase dietary supplements

Symptoms should response to dietary management within days. If they persist despite these measures, further advice from your physician should be sought.

Further information

MicroGnome, 27thJune, 2010.


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