Does Sunscreen Expire?
Sunscreens are designed to remain at original strength for up to three years. This means that you can use leftover sunscreen from one year to the next. Some sunscreens include an expiration date, a date indicating when they're no longer effective. Generally, a liberal application is 1 ounce — the amount in a shot glass — to cover all exposed parts of the body. Using this amount, you shouldn't have any bottles of sunscreen that last more than 3 years. Apply sunscreen generously 20 to 30 minutes before going outdoors and reapply about every two hours, or more often if you're swimming or sweating. Be sure to rub the sunscreen in well.