Sunscreen cannot claim immediate protection on application, or protection for more than two hours without reapplication, unless special approval is obtained by the FDA.
4. Water-Resistant claims:
Sunscreens that claim to be water-resistant will only have two reapply options listed, of 40 minutes or 80 minutes, while swimming or sweating, based on standard testing.
Sunscreen that is not water-resistant must have labeling telling the consumer to use one that is, while swimming or sweating.
All sunscreens must list the drug information on the back or side of the container. There are 17 active ingredients approved for sunscreen protection by the FDA though sunscreen may also list other ingredients.
Cosmetics that offer sunscreen protection must also abide by the FDA labeling guidelines.
One of the easiest ways to know if the sunscreen you plan to purchase meets proper protection is to look for The Skin Cancer Foundation's Seal of Recommendation.
The Foundation implemented new standards that divide sunscreens into “Daily Use” for those with a SPF of 15 and “Active Use” for those with an SPF of 30 and above that also show proof of water-resistance.
Sunscreens should be applied at least 30 minutes before going outside, reapplied every two hours when spending time outdoors, and immediately after swimming or heavy sweating. At least one ounce should be used to cover the entire body.
In addition, if a person is taking photosensitive drugs, they should be aware that they have an increased risk from sun exposure. A list of many photosensitive drugs can be found here.
The Skin Cancer Foundation did state that there is no reason to throw away last year’s sunscreen. The shelf life of sunscreen is typically two to three years if stored in a cool place, since heat can break it down.