Babies don’t have a very strong immune system. That means they don’t have any built-in protection to fight off the bugs that cause illnesses like diarrhoea and sickness.
The bacteria that cause these illnesses are very common and can easily get onto feeding equipment. Bacteria can grow in any leftover milk in baby’s bottles, and transfer to the bottles from your hands, the atmosphere and even tap water.
When this goes into baby’s mouth, the bugs can be transferred to baby and can make them very poorly. That is why it is really important to thoroughly wash and sterilise feeding equipment, and to use cooled boiled water to prepare formula.