The World Health Organization has Five Moments for washing hands: 1  before patient care. 2  after environmental contact. 3  after exposure to blood/body fluids. 4  before an aseptic task, and. 5  after patient care.
This means that you can use leftover sunscreen from one year to the next. Some sunscreens include an expiration date â a date indicating when they're no longer effective. Discard sunscreen that is past its expiration date. If you buy sunscreen that doesn't have an expiration date, write the date of purchase on the bottle and be sure to throw it out within three years. Also, discard sunscreen that has any obvious changes in color or consistency.
Most of the whitening products we use in our office have a shelf life of 18 months. Once the whitening strips expire, they will not cause any harm to your teeth, but their whitening effectiveness may be reduced or even completely eliminated. For best results, use your whitening strips BEFORE they expire.