Answer by Integrative Clinical Pharmacist Scott Berliner RPh:
The Food and Drug Administration (FDA) has taken steps to regulate labeling of sunscreens. These changes won’t affect consumers until 2012. For now, here’s what you need to know when choosing a sunscreen:
The SPF (Sun Protection Factor) refers to the amount of time a sunscreen will prevent burning for most people (All individuals do not have the same skin type or the same propensity to redness.) The SPF number indicates how many times a person’s own reddening time is extended by the lotion, oil or sunblock stick. For instance, if a person exposed to the sun starts getting red in 15 minutes, then an SPF of 15 would give that person 15 X 15 minutes or 225 minutes in the sun before turning red.
The SPF does not indicate the product’s quality, and a sunscreen with an SPF of 30 is not necessarily better than one with an SPF of 15, but it does provide protection for a longer period of time. The actual length of time a person can expect the screening agent to protect them is not the same for everyone, and may even differ for the same individual under different circumstances. For example, swimming will change the constant as will visiting locations closer to the equator.
“Sunscreen” and “sunblock” are not synonymous. In fact, new FDA regulations will eventually phase out the word “sunblock.” These products, for people with sensitive or traumatized skin, typically contain zinc oxide or titanium dioxide and provide more complete blocking of both UVA and UVB rays, yet are considered safe for use on a daily basis even in skin deemed to be “sensitive.” These physical blocks are considered safer because they are not absorbed into the skin but actually stay on the surface and reflect the sun’s UVA and UVB rays. Many of these agents will leave an opaque color on the skin because they are not absorbed, hence some pick the chemical screens instead.
UVB rays cause sunburn. UVA rays penetrate more deeply and are linked to skin damage and cancer. Dermatologists say titanium dioxide, zinc oxide, methoxycinnamate and avobenzone (or Parsol 1789, which may have carcinogenic tendencies) stop UVA from reaching your skin, so check for these ingredients. Avoid PABA, benzophenone and the Parsol 1789 as these may have more than allowable negative effects.
The Center for Integrative Medicine chooses sunscreens based on quality, effectiveness and lack of toxicity. Interestingly, it is not the most expensive products that make the top of the list. The Environmental Working Group’s site (EWG.org) is one resource for checking the toxicity of many common household items. You can also sign up for their “Skin Deep” division, which rates sunscreens, sunblocks and other agents used for sun protection.
Sunscreens can take up to 30 minutes to be absorbed, therefore they should be applied before going into the sun. Regardless of the instruction on the label it is best to reapply every 2 hours. Depending on your activity, this may need to be done more often, paying attention to the more sensitive parts of the body that are often neglected including your ears, the top of your feet and the top of your head. If in doubt, reapply.
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