Science Questions

Why are some babies allergic to milk?

Sun, 31st Oct 2010

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Kathleen, Lowestoft asked:

I understand about allergies, how people can become allergic to things as they go along in life, but what Iíd like to know is, how can a baby be born that is allergic to breast milk and all forms of milk? What happens?


Chris -   You shouldnít have a baby thatís allergic to breast milk because breast milk has proteins in it that we make in our own body and therefore, itís very difficult to be allergic to things like that.  Breast milk is a pretty special mixture.

You do get babies that won't breastfeed properly and so, parents then in frustration would turn to bottled feeds - because the baby needs the energy, and the baby is not growing fast enough so you put the baby on bottled feeds to try and get the baby growing a bit quicker.  Then a baby can show an allergic reaction to whatís in the bottled feed.  Thatís because bottled milk does contain cowís milk proteins and as you know, the bulk of what we get in milk is things like calcium plus protein, and the body can recognise the cowís milk proteins as being foreign, and thatís one reason.

Another thing that is in milk is lactose and humans have evolved, not necessarily to eat milk.  And so, some people, especially people who are white and from our part of the world, actually may have a thing called lactose intolerance, and this is where they can't make an enzyme which is normally expressed in the intestine and breaks down lactose which is a sugar.  Itís two glucose molecules stuffed together.  They lack an enzyme, lactase which will break those molecules apart.  And so, the lactose carries on down the intestine and it pulls water into the intestine, causing bloating and diarrhoea-like symptoms and thatís lactose intolerance.  People who eat a lot of milk or dairy products, if they overdo it and they have that particular deficiency will get those symptoms.  So thatís another reason why a baby might be intolerant.

Some babies are just very allergic to things and some of the other things weíre discussing earlier, with things like having lots of antibiotics or having a caesarean section can make some people more prone to develop more allergies as they go along.


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