Signs of Lactose Intolerance You Must Look Out For

Don't ignore these symptoms of lactose intolerance as they can cause other health problems in the long run.

3 min read
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According to the doctors of Mayo Clinic, lactose intolerance is the inability of the body to break down the lactose sugars, which are commonly found in dairy products like milk and yogurt. This happens when the small intestine stops making the lactose-digesting enzyme called lactase, due to which the undigested lactose is carried down to the large intestine.

The enzymes in the large intestine are unable to digest food and thus cause problems of gas, bloating, and diarrhea. The condition can also be termed lactase deficiency.

In this article, we'll highlight the major signs of lactose intolerance that you can look out for.


According to the doctors of Cleveland Clinic, about 30 million Americans suffer from lactose intolerance, and though it might not be a serious problem, it is definitely an unpleasant one that onsets after 1-2 hours of ingesting milk or dairy products.

Lactose Intolerance: Signs To Look Out For

According to Healthline, about 70% of people worldwide suffer from lactose intolerance but they are not generally aware of it. The common side effects of the condition include diarrhea, bloating, gas, constipation, etc., due to lactose malabsorption. Few rare ones include headache, allergy, and eczema, but more studies are required to confirm the relation.

A few common symptoms and their causes include:

Stomach Ache 

According to PubMed Central, lactose, when not broken down, is passed down from the gut to the colon in its undigested form. There, it is fermented by the naturally occurring bacteria in the gut known as 'microflora', which causes the release of hydrogen, methane, carbon dioxide, and short-chain fatty acids.

These acids and gases cause cramps, pain, and bloating in the lower region of the belly, especially around the belly button.


According to the US NIH, bloating is also a common side effect of consuming milk or other lactose-containing dairy products and it is caused when the gas and water mix in the colon, which results in stretching of the gut walls, also known as distension.


According to the doctors of Mayo Clinic, bloating is not related to the amount of lactose ingested but the sensitivity of a person to distention. And that is why the levels of bloating can differ from person to person and can also result in vomiting or nausea at times.

Excessive Gas

As mentioned before, lactose is not digested or broken down in the digestive system and is passed unbroken to the gut where the fermentation takes place, which results in the production of gases like hydrogen, methane, and carbon dioxide.

The levels of people being troubled by gas differ from person to person due to the difference in gas reabsorption in the colon and the efficiency of microflora.


According to the US NIH, constipation due to lactose intolerance is characterised by hard, infrequent, incomplete bowel movements, which cause excessive straining and stomach discomfort.

According to Healthline, it is a more common symptom of lactose intolerance than diarrhea and is the result of methane gas, which slows down the movement of food through the gut. People should consult their doctor as this may also be a cause of other problems, like hypothyroidism, irritable bowel syndrome, Parkinson's disease, hemorrhoids, etc.


According to the US NIH, the increase in the frequency of passing stool and changes in its volume and liquidity are a few of the characteristics of diarrhea. Excess consumption of lactose-containing dairy products leads to an increase in the water of the gut (due to the leftover lactose and acids), which increases the liquid content in the stool passed.

Other Symptoms 

According to the doctors of Mayo Clinic, the symptoms of lactose intolerance are usually related to gastrointestinal problems but there are many other symptoms as well which may be rare and might be confused for the symptoms of milk allergy:

  • Headache

  • Oral ulcers

  • Fatigue

  • Muscle and Joint pain

  • Lack of concentration

  • Rashes

  • Eczema

  • Urination related problems

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Topics:  Lactose Intolerance 

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