After each feeding, bottles should be cleaned. If your infant does not complete a bottle within two hours, discard the unfinished formula. If breast milk or formula is introduced to a partially used bottle, or if a used bottle is just washed rather than cleansed, germs can proliferate fast. These organisms can be transmitted to your infant through his mouth. Some bacteria may even remain active after the formula has cooled down. There are several ways you can recycle or dispose of unused breast milk or formula-including donating it to a friend or family member, bringing it to a drop-off location, or recycling it. For more information on these options, see the sections below.