Secondary Lactose Intolerance

Secondary lactose intolerance is when you become temporarily lactose intolerant because of an underlying condition or surgery that has damaged your digestive system. This damage disrupts lactase enzyme activity, reducing the capability of your small intestine for digesting lactose.

Who are affected?

Damage to your digestive system, more specifically your small intestine can occur at any time throughout your life. So, secondary lactose intolerance can affect anyone at any age. Individuals at particular risk are those who have undergone surgery or have an underlying condition that has damaged there small intestine. It has also been found that some medications may affect the small intestine.


There are three main ways your small intestine can become damaged to cause secondary lactose intolerance:

  • Underlying condition -  including intestinal diseases and inflammatory bowel diseases
  • Surgery
  • Certain medications

The following are more specific causes of secondary lactose intolerance:

  • Gastroenteritis – a viral infection of the stomach and small intestine.
  • Coeliac disease – a bowel condition caused by an adverse reaction to the protein gluten.
  • Ulcerative colitis – chronic (long-term) condition of the colon.
  • Crohn’s disease – a chronic inflammatory condition of the lining of the digestive system.
  • Chemotherapy – used for treating cancer

Secondary lactose intolerance is normally only temporary, but in long-term chronic conditions such as Crohn’s disease it can be long lasting and the damage can be permanent.


After the initial infection or inflammation of the digestive system has resolved, the cells responsible for the enzyme lactase return to normal function and lactase activity increases. Normally, secondary lactose intolerance resolved of its own accord. Treatment of the underlying condition is the best way to return lactase activity to normal levels.

If you experience temporary lactose intolerance you should try to avoid any lactose containing foods from your diet, while you recover from the illness/injury. Then after a couple of days, when symptoms appear to improve, start to reintroduce dairy foods to your diet.

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