If you do not disinfect the baby's bottle, there is a risk of bacteria and other contaminants in the bottle and milk. And you can increase your child's risk of getting sick. If Avent Bottles are not sterilized, bacteria can grow in bottled milk or formula, and your baby may develop gastrointestinal problems such as diarrhea, vomiting, and cramps by drinking the bacteria.  Even so, it can lead to more serious health problems such as meningitis, sepsis, and pneumonia. So, you can boil the bottles in water to disinfect your child's Avent Bottles or use a dishwasher with a disinfection set.