How does zinc oxide filter sunlight?
Zinc oxide is a mineral filter, alongside titanium dioxide. It protects mainly by absorbing ultraviolet radiation, and mineral sunscreens can also reflect some rays. The word 'physical' is a stubborn name for a filter that mostly absorbs UV. Ingredient comparisons list zinc oxide as covering UVB and both UVA bands. UVA can pass through window glass and contribute to early skin aging; UVB is the main cause of sunburn. No sunscreen blocks every ultraviolet ray, so zinc oxide reduces exposure rather than switching the sun off.12
What should the sunscreen label say?
Choose a sunscreen labelled broad spectrum, SPF 30 or higher, and water resistant. SPF mainly measures protection against UVB; broad spectrum indicates protection against UVA and UVB. SPF 30 blocks about 97 percent of UVB rays when used as directed, and higher SPF blocks slightly more, but no sunscreen blocks all UVB. A high SPF does not let you stay outside longer before reapplying. SPF is not a stopwatch, even if the number looks like one. Most people apply only 20 to 50 percent of the amount needed to reach the SPF on the label, so applying enough matters more than shopping for a larger number.12
What should I expect from a zinc oxide sunscreen?
Mineral sunscreens start working as soon as they are applied. The American Academy of Dermatology still advises applying sunscreen to dry skin 15 minutes before going outdoors. Mineral formulas are often thicker and harder to spread than chemical sunscreens, and zinc oxide or titanium dioxide can leave a visible white cast, especially on darker skin tones. A white cast is the mineral filter's least discreet product demo. Micronized or ultrafine mineral formulas can reduce white residue, and a tinted sunscreen can help hide it.123
Who might prefer zinc oxide?
A mineral sunscreen with zinc oxide can be a good option for sensitive or allergy prone skin. Dermatologists recommend mineral sunscreens for sensitive skin, and a Cleveland Clinic dermatologist notes that physical blockers can be less irritating. Mineral formulas are also an option for younger children. For babies younger than six months, the American Academy of Dermatology advises avoiding sun exposure where possible rather than relying on sunscreen alone.24
How should I apply sunscreen with zinc oxide?
- 1Apply sunscreen every day to skin not covered by clothing if you will be outside, including on cloudy days. Apply it to dry skin 15 minutes before heading outdoors.
- 2Use at least 1 teaspoon for your face. Most adults need about 1 ounce to cover exposed skin on the body; use more if needed for your body size. Cover the neck, ears, tops of the feet, and top of the head.
- 3When outdoors, reapply about every two hours, or after swimming or sweating, following the directions on the bottle. No sunscreen is waterproof or sweatproof, so water resistance does not remove the need to reapply.
- 4Use shade and sun protective clothing as well as sunscreen. Sunscreen is only one part of reducing ultraviolet exposure.
Zinc oxide vs titanium dioxide
| Mineral filter | Main UV contribution | Which to choose |
|---|---|---|
| Zinc oxide | Stronger contribution in the UVA range, with coverage across UVA and UVB bands. | Choose it when you want a mineral filter with more UVA emphasis. |
| Titanium dioxide | Stronger contribution in the UVB range; ingredient comparisons show less coverage of the longer UVA band. | Choose it when UVB emphasis is the priority, and check that the finished sunscreen is labelled broad spectrum. |
Some mineral sunscreens combine zinc oxide and titanium dioxide. The ingredient name alone does not tell you how a finished sunscreen will look or feel.25
What does the FDA say about zinc oxide?
In the United States, the FDA's proposed over the counter sunscreen order proposes GRASE status for sunscreens containing zinc oxide and titanium dioxide. The FDA describes this as a proposal, not a final order.6
Where this answer comes from
- 1Sunscreens: A Complete Overviewdermnetnz.org
- 2Sunscreen FAQsaad.org
- 3Mineral vs. Chemical Sunscreen: Which Is Better?health.clevelandclinic.org
- 4Facebooknewsroom.clevelandclinic.org
- 5Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectivenesspmc.ncbi.nlm.nih.gov
- 6Questions and Answers: FDA’s regulatory actions on over-the-counter sunscreenfda.gov
