Weaning after 17 weeks may help prevent food allergies

Solid food after 17 weeks can 'boost a breastfed baby's immune system'


Introducing your baby to solid food from 17 weeks, alongside breastfeeding, may help prevent your baby from developing food allergies, suggest researchers from the University of Southampton.


But offering your baby solid food before 17 weeks seems actually to make it more likely that your baby will develop food allergies. 

What does the study say exactly?

We already know that your baby’s gut is intolerant of solid food before 4 months– which is why all experts agree that you should never start to wean your baby before 17 weeks. The official Department of Health recommendation is to wait until your baby is about 6 months old.

The Southampton research confirms this view of gut intolerance before 4 months: the babies in this study who went to to develop food allergies were weaned earliest – at, roughly, 16 weeks or earlier. 

What is more interesting is that the research team, led by dietician and senior research fellow Dr Kate Grimshaw, also found that breastfed babies who were weaned after 17 weeks – including those weaned before the officially recommended starting age of 6 months – seemed actually to be protected against developing food allergies.

“Our findings suggest 17 weeks is a crucial time point,” says Dr Grimshaw. “Solid-food introduction before this time appears to promote allergic disease, whereas solid food introduction after that time point seems to promote tolerance.”

It’s important to know that this suggested ‘protective effect’ only applies to babies who are still breastfeeding – and also that the number of breasted babies included at this point in the study was very small (because so many mothers had stopped breastfeeding by 17 weeks).

What are the figures behind the evidence?

The study was funded by the UK Food Standards Agency and it recruited 1140 infants from the Hampshire area. Of these children, 41 went on to develop a food allergy by the time they were two years old. The feeding of these infants was compared to the feeding of 82 breastfed infants who did not develop an allergy.

So, although the recruited group was large, the number of children who developed an allergy and of those who did not was very small.

What do other experts say?

In 2001, the World Health Organisation (WHO) advised that babies should be exclusively breastfed for the first 6 months and not given any solid food until this point. This advice was based on a review of a large number of studies conducted worldwide.

In 2003, this WHO advice was adopted by the Department of Health (DOH), and the official recommendation for parents in the UK is to wait until 6 months to start your baby on solids.

In 2012, a review of evidence published by the British Medical Journal suggested that weaning babies between 4 and 6 months may, in fact, be fine – or even beneficial for some babies.

So, what should mums do?

This new research is fascinating but it doesn’t mean we should all suddenly be weaning our babies at 17 weeks.

The ‘protection’ against food allergies that the researchers found seems to kick in at 17 weeks, for sure, but it also seems to apply to babies weaned at any point from 17 weeks to 6 months. And, remember, this protection only seems to extend to babies who are also being breastfed.

The official DOH recommendations to wait until 6 months before starting your baby on solids remain unchanged.


We do know that many mums do want – or think they should – start to wean before 6 months. If your baby is over 17 weeks but under 6 months and you think he or she is ready to start weaning, you should always check first that your baby is showing the physical signs of being ready to wean. And if the signs are there, you should speak to your GP or health visitor before breaking out the weaning spoons, especially if you have a family history of allergies.

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