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Cow's Milk Allergy Vs Lactose Intolerance

What’s the difference between Cow’s Milk Allergy and Lactose Intolerance?

Cow’s milk is made up of lots of different components, for example proteins (such as casein and whey), milk sugar (called lactose) and fat.

The allergic reaction happens because the immune system mistakes the proteins in cow’s milk to be a threat, when in fact they should be harmless. It then releases chemicals such as histamines and others – it’s these chemicals that trigger the signs and symptoms of an allergic reaction.

Lactose intolerance is triggered by the lactose sugar in cow’s milk. In people with lactose intolerance, the digestive system can’t fully digest this milk sugar, because it doesn’t make enough of the lactase enzyme. So instead of being digested and absorbed, the lactose stays in the gut and feeds the gut bacteria, which release acids and gases that cause the symptoms of lactose intolerance.

Who gets it?

Cow’s milk allergy tends to affect younger children under the age of 3 years. Most will grow out of this food allergy as they get older, often by the time they start school.

Only in very rare cases does lactose intolerance affect babies from birth (called congenital lactase deficiency). In this case, the person remains lactose intolerant for life.

What are the symptoms?

Cow’s milk allergy and lactose intolerance can share some of the same signs and symptoms, including feeding and bowel problems such as:

  • Wind
  • Diarrhoea
  • Bloated tummy
  • Tummy aches and cramps
  • Tummy rumbling
  • Feeling sick


However, since cow’s milk allergy involves the immune system, babies who are allergic to cow’s milk protein will also show allergy symptoms like an itchy rash, wheezing, or runny noses and coughs. These aren’t seen in lactose intolerance, as this condition doesn’t involve the immune system.

Another difference is that with cow’s milk allergy, even a small amount of cow’s milk protein could give your baby an allergic reaction. In contrast, many people with lactose intolerance can often eat small amounts of milk products without noticing any symptoms.

Allergy Awareness Week 2017 will be taking place from 24 to 31 April 2017. More information about the campaign can be found on Allergy UK's Website or on Twitter: #AllergyAwarenessWeek

For further information a fact sheet on Milk Allergy has been produced by Allergy UK, which can be downloaded here.