Zinc oxide is a white mineral powder used as a sunscreen filter. It is strongest against UVA, the longer rays linked to tanning and aging, and is often paired with titanium dioxide for broad protection. Smaller particles reduce the white cast, and studies on living skin found they stay on the surface.
- Helps with
- sunburn, sun spots and tanning, white cast from mineral sunscreen, worries about nanoparticles
- Evidence
- Strong. A long-established UV filter that the FDA's proposed sunscreen rule listed as generally recognized as safe and effective; skin-penetration studies on living volunteers are small but consistent.
- Works well with
- titanium dioxide, moisturizer under sunscreen
- Be careful with
- broken or damaged skin (penetration not fully studied)
What does zinc oxide do for skin?
Zinc oxide sits on top of your skin and filters ultraviolet light before it reaches the living cells underneath. It is the ingredient behind most mineral sunscreens. Think of the slow tan that builds on your forearms during a cloudy summer, or the brown spots that darken each year on your cheekbones; much of that comes from UVA, and UVA is where zinc oxide does its best work.
How does zinc oxide work?
Sunscreens have to cover two bands of light: UVB, from 290 to 320 nanometers, which mainly causes sunburn, and UVA, from 320 to 400 nanometers, which reaches deeper. A 2011 review explains that titanium dioxide is more effective against UVB and zinc oxide against UVA, so formulas often combine the two for broad protection. The same review notes that the FDA expects a sunscreen’s UVA protection to be at least one-third of its overall SPF.
Why does zinc oxide leave a white cast?
Because the particles reflect and scatter visible light as well as UV. Larger, micro-sized particles look opaque on skin, the chalky film many people remember from old beach sunscreens. Manufacturers switched to nanoparticles, under 100 nanometers, to make that opaqueness disappear. The trade-off, the 2011 review notes, is that very small particles can shift the balance between UVA and UVB protection, and mixing micro- and nano-sized zinc oxide may help.
Do zinc oxide nanoparticles get into your body?
Studies on living volunteers say they stay in the outer layer. In a 2016 study, zinc oxide particles of about 75 nanometers were rubbed in with massage and with the skin repeatedly flexed; they remained in the top layer and in skin creases, with no damage to the cells below. A research group that spent ten years imaging skin this way concluded that “nanoparticle zinc oxide particles do not penetrate human skin when applied to various skin types with a range of methods of topical sunscreen application.” A 2019 review agreed that most studies find no penetration into living skin, while noting some evidence that damaged skin may behave differently.
How long until you notice a difference?
Sunscreen protection starts as soon as a full layer is on. The difference you notice over months is what does not happen: less tanning and fewer new sun spots. Our guide to how much sunscreen to use on your face explains what a full layer looks like.
How do you use zinc oxide?
Apply it as the last step of your morning routine, after moisturizer, and reapply after sweating, swimming or toweling off. Our guide to the best sunscreen for humid weather covers how sweat moves sunscreen around.
Who should be careful with zinc oxide?
It is one of only two filters, with titanium dioxide, that the FDA’s proposed sunscreen rule listed as generally recognized as safe and effective among those on the US market, according to the 2020 review. The open question is broken skin: the 2019 review called for more research on damaged skin, so on cuts or raw patches, cover up rather than relying on sunscreen alone. As with any new product, patch test first if your skin reacts easily.
- Smijs TG, Pavel S. Titanium dioxide and zinc oxide nanoparticles in sunscreens: focus on their safety and effectiveness. Nanotechnol Sci Appl. 2011;4:95-112.
- Leite-Silva VR, et al. Effect of flexing and massage on in vivo human skin penetration and toxicity of zinc oxide nanoparticles. Nanomedicine (Lond). 2016;11(10):1193-205.
- Mohammed Y, et al. Noninvasive in vivo human multiphoton microscopy: a key method in proving nanoparticulate zinc oxide sunscreen safety. J Biomed Opt. 2020;25(1):1-19.
- Vujovic M, Kostic E. Titanium dioxide and zinc oxide nanoparticles in sunscreens: a review of toxicological data. J Cosmet Sci. 2019;70(5):223-234.
Editorial content, not medical advice.