Aoife Hearne: I'm worried about giving formula milk to my baby

Research suggests that breast milk has a favourable influence on the infant's gut and microbiome, which protects against the development of allergies. The majority of research focuses on exclusive breastfeeding for the first six months of life

Tue, 02 Sep, 2025 - 00:50

Aoife Hearne

Dietitian

I'm breastfeeding my five-month-old baby. Now and again, I give him a formula bottle if my supply is low or if I'm going out for the night.

A friend recently told me that babies are at greater risk of developing allergies if they are not breastfed exclusively until six months. I'm worried as allergies run in my family. Could she be right?

You have brought me right back to hazy early days with a young baby. Just when you think you have things figured out, you’re thrown a curveball, which may be what has happened here.

To begin, well done on choosing to breastfeed and reaching five months. It can be easy to view things as all or nothing, but I’m not sure this approach is helpful. Just one teaspoon of breast milk contains as many as three million germ-killing and immune-building cells, so please remember that any breastmilk you can give your baby is beneficial and worth it.

To maintain a supply, you need to 'place an order' for milk the next day, which can be achieved by your baby suckling at your breast or by using a breast pump.

If you have concerns about the risk of food allergies, you may want to consider pumping your milk rather than giving your baby infant formula. This will not only help maintain your supply but also ensure you have a backup feed in the fridge or freezer if you have a night out planned. (For more information about pumping, check out HSE, La Leche League, and KellyMom.)

In terms of allergies, research from multiple research groups worldwide consistently points to the same fact: the longer you breastfeed, the more beneficial it is for the baby. Extended breastfeeding has been shown to help reduce the incidence of eczema, asthma, wheezing, and allergic rhinitis.

In addition to the immune-building cells present in breast milk, research published in Nutrients (2020) suggests that breast milk has a favourable influence on the infant's gut and microbiome, which protects against the development of allergies. The majority of research focuses on exclusive breastfeeding for the first six months of life.

Looking specifically at food allergy, research published in Paediatric Allergy and Immunology in 2019 suggests that exclusively breastfed babies who receive infant formula top-ups within the first 24 hrs of life have a significantly increased risk of developing cow's milk protein allergy (CMPA). Some studies suggest that this unnecessary practice can increase the risk of CMPA by sevenfold in many cases.

According to the Irish Food Allergy Network (IFAN.ie), when it comes to the prevention of food allergies, there is no evidence that allergy prevention can be achieved while a baby is exclusively breastfed. Current proven methods of risk reduction only begin when the infant is introduced to solid foods.

Introducing solids is a critical time for preventing food allergies. The current advice is to start solids at the six-month mark while continuing to breastfeed until two years and beyond. Of particular importance, it is recommended to introduce all potential food allergens (such as peanuts, eggs, and wheat) at this time, rather than delaying these foods out of fear of developing an allergy. Once introduced, these foods should remain part of the weekly offering at meals and or snacks.

If parents or carers have any concerns about food allergy symptoms, such as a rash or swollen lips, they should contact their GP immediately.