The medications in prescription medications have properties that will expire. Just like food will rot, medications will become less effective. The expiration dates are suggestions, although they are suggestions that I suggest you take.
Few things stay the same, food will rot due to bacteria and other tiny creatures eating it, metals will rust when exposed to oxygen. Medications are similar, when exposed to oxygen or other gases in the air it changes them. Proper storage can push the expiry dates, but temperature and an airtight seal will be key to long term storage. Your medication has probably sat in your bathroom medicine cabinet, water gets into them after showers, you’ve surly opened it a few times and exposed it to the air. The heat in your bathroom alone can effect the medication.
Creams usually have a small percentage of some anti-bacteria agent. This agent is what will change over time. It may simply become ineffective, although they could end up causing further harm if you continue to use the product after the expiry date. Probably the biggest reason you shouldn’t use an expired cream is that you will expect it to work, and when it doesn’t the infection can become worse, causing you more damage.
