Why do common household items (shampoo, toothpaste, medicine, etc.) have expiration dates and what happens once the expiration date passes?

Question

Why do common household items (shampoo, toothpaste, medicine, etc.) have expiration dates and what happens once the expiration date passes?

In: Other

Answer 1

I accidentally used some toothpaste that was expired by a couple of years. It was extremely unpleasant.