Dr. Norman Levine: The other issue often raised involves chemicals in sunscreens. Please describe any issues regarding specific chemicals and their harm to the patient.
Dr. Darrell S. Rigel: I always get a laugh when I see sunscreens claiming to be “chemical-free,” because there are chemicals in everything. There is no such thing as a chemical-free sunscreen. With several of the sunscreen agents that are comprised of all chemicals, some studies have suggested there might be potential problems.
One chemical that always rises to the top is oxybenzone, or all of the benzophenones. There was a study done in rats where they fed female rats high levels of benzophenones. What they found was that some of the rats had uterotrophic effects from the ingestion of the benzophenones.
Further research on this showed that for humans to get the same levels of benzophenones as the rats would equate to applying the sunscreen on the entire body every day at the amount rated by the FDA, which is 2 mg/sq cm. Nobody uses sunscreen at that concentration, but if you were to, it would take 34 years of daily application to get as much benzophenone as those rats were given in that period of time.
If you just use sunscreen in the way people normally use it on a regular basis — on the face or head and neck or the back of the hands — it would take over 200 years to get the dose that those rats received. So obviously, anything in extreme is bad. Although several sunscreen agents have been implicated at least in some studies, overall when researchers looked at them in more depth or did more studies, the sunscreen agents were shown to be safe.