The ingredient list on a bottle of sunscreen reads like a college level chemistry textbook. To help decipher what those chemicals are, Dr. Mercola put together the following list.
Octinoxate (Octyl Methoxycinnamate)
The most widely used sunscreen ingredient, known for its low potential to sensitize skin or act as a phototallergen. Estrogenic effects are noted in laboratory animals as well as disruption of thyroid hormone and brain signaling. Has been found to kill mouse cells even at low doses when exposed to sunlight!
Associated with photoallergic reactions. This chemical absorbs through your skin in significant amounts. It contaminates the bodies of 97% of Americans according to Centers for Disease Control research. Health concerns include hormone disruption and cancer.
Octisalate is a weak UVB absorber with a generally good safety profile among sunscreen ingredients. It is a penetration enhancer, which may increase the amount of other ingredients passing through skin.
Avobenzone (Parsol 1789)
Primarily a UVA-absorbing agent, sunlight causes this unstable ingredient to break down into unknown chemicals, especially in the presence of another active, Octinoxate.
Produces oxygen radicals when exposed to UV light.
Research indicates it is a weak hormone disruptor, forms toxic metabolites, and can enhance the penetration of a toxic herbicide.
Micronized Titanium Dioxide
Sunscreens with micronized titanium dioxide may contain nanoparticles. Micronized TiO2 offers greater sun protection than conventional (larger) particles. These small particles do not penetrate skin but may be more toxic to living cells and the environment. Inhalation of powders and sprays is a concern.
Micronized Zinc Oxide
Same as Micronized Titanium Dioxide, above.
Appears safe for use on skin, due to low penetration but inhalation is a concern.
Ensulizole (Phenylbenzimidazole Sulfonic Acid)
Known to produce free radicals when exposed to sunlight, leading to damage of DNA, this UVB protector may have the potential to cause cancer.
Nano Zinc Oxide
Nano zinc oxide offers greater sun protection than larger zinc particles. Comparatively little is known regarding potential health effects of nanoparticles. They do not penetrate healthy skin, and thus appear to pose a low health risk in lotions. Inhalation of powders and sprays is a concern.
Nano Titanium Dioxide
Same as Nano Zinc Oxide, above.
Zinc has a long history of use in sunscreen and other skin care products; little absorption and no adverse health effects are reported.
Padimate O (Octyl Dimethyl PABA / PABA Ester)
A derivative of the once-popular PABA sunscreen ingredient, research shows this chemical releases free radicals, damages DNA, has estrogenic activity, and causes allergic reactions in some people.
1 study found that it produces damaging reactive oxygen species when exposed to sunlight.
2 hours of sunlight can degrade as much as 40% of this active ingredient. Low skin penetration.
Methylene Bis-Benzotriazolyl Tetramethylbutylphenol
Not an approved active ingredient in the U.S. Few studies exist on this chemical. It is photostable and does not absorb through your skin.
Can cause skin and eye irritation. Does not penetrate your skin to a large degree, but enhances the ability of other chemicals to penetrate.
Not approved for use in United States sunscreens. Concerns about hormone disruption.
Here is an journal article from pubmed, Liquid chromatographic assay for common sunscreen agents: application to in vivo assessment of skin penetration and systemic absorption in human volunteers. To sum up the study, it demonstrated significant penetration of all sunscreen agents into the skin. All those chemicals you slather on your skin are getting into your bloodstream.
To further help navigate all this information a site by EWG allows you to look up your sunscreen to see how dangerous it may be and also find safe alternatives.
I hope this information helps you to find a safe sunscreen.