Zinc oxide and titanium dioxide are the only mineral compounds approved by the FDA for use as active sunscreen ingredients. How do they differ? Which is better? Read on.
Cut to the chase. Which is better?
In a showdown between zinc oxide and titanium dioxide, zinc oxide is the clear winner in all but cost (zinc oxide is more expensive). We’ve outlined the comparison in three main categories: sun protection, chemistry, and effect on biology.
In basic terms, UVB rays affect the skin’s surface (think B for Burn), while UVA rays affect deeper tissues (think A for Aging). Broad-spectrum sunscreen defends against both UVA and UVB radiation to protect skin from both deep tissue and surface damage.
Zinc oxide absorbs UV rays and converts the energy to infrared heat, which radiates safely away from the skin surface. It’s the most effective sun protector available, blocking out both shorter and longer wave UVA rays as well as all UVB rays. In this respect, zinc oxide is better than titanium dioxide (across a greater range of UVA wavelength). In fact, zinc oxide is the only active sunscreen ingredient that covers the entire UVA/UVB spectrum by itself.
Titanium dioxide absorbs and scatters ultraviolet rays. Compared to zinc oxide, titanium dioxide is as effective at blocking UVB rays, but it's somewhat less effective for short UVA rays (UVA II), and almost completely ineffective against long UVA rays (UVA I). In short, titanium dioxide is inferior to zinc oxide for broad-spectrum coverage. To increase protection, titanium dioxide can be combined with chemical UVB and UVA blockers and/or zinc oxide, but products that rely solely on titanium dioxide as an active ingredient will allow significant UVA damage while effectively preventing UVB rays from giving the user any natural cues to get out of the sun.
Zinc oxide (ZnO) is made using zinc, a critical mineral element used to keep humans healthy and found in many multivitamins. ZnO occurs naturally in the mineral zincite, but most of the commercial products are made by the high-temperature oxidation of zinc ore, which is melted then vaporized into a gas where it reacts with oxygen to form solid ZnO. Zinc oxide is an inorganic compound and is insoluble in water. It has antimicrobial properties that help wounds heal more quickly, and it is non-comedogenic — i.e. it’s oil-free and won’t clog pores.
Non-nano zinc oxide is highly stable under most conditions, including when hit with UV rays. It absorbs UV energy via bandgap absorption (it reflects and scatters visible light, that’s why it looks white), preventing skin penetration and cell damage. Zinc oxide holds tight to its electrons when it absorbs UV energy, limiting the creation of free radicals that cause oxidative damage or increase the risk of skin cancer.
Titanium dioxide (TiO2) is derived from titanium, a heavy metal that’s toxic to humans and has poorly studied exposure risks. It’s produced from either ilmenite, rutile or titanium slag, using either sulfuric acid or chlorine in a complex industrial chemical processes. Stable under most conditions, Ti2O is crucialy LESS stable when hit with UV rays, creating significant amounts of free radicals that do oxidative damage and increase aging processes.
Effect on Human + Marine Biologies
Non-irritating and easy on sensitive skin, zinc oxide has been used in skincare for 1000s of years. A skin protectant widely used in treating various forms of skin irritations, it’s used in diaper creams, calamine lotion, and toothpastes. Zinc oxide doesn’t sting eyes.
Zinc is a critical mineral nutrient that keeps us healthy. Zinc oxide is the ONLY sunscreen active ingredient that’s been tested and FDA approved for use on babies less than 6 months old. It’s also great for use around the eyes, as it won’t cause stinging.
Zinc oxide is a powdered mineral that doesn’t dissolve in seawater, and in its non-nano variety (meaning its particles are all large enough to not seep through skin pores or enter marine biosystems) it rapidly settles to the seafloor and becomes part of the sediment. Non-nano (larger than 100 nanometers) zinc oxide is safe for reefs and marine life, but NANO zinc oxide particles (smaller than 100 nanometers) can be ingested by marine animals including coral, causing internal damage, and when washed off into the ocean, they can react with UV rays to generate hydrogen peroxide which can be toxic to phytoplankton—a vital nutrient to many reef and coral species.
Kenneth Howe, a dermatologist at Wexler Dermatology says, “Mineral sunscreen nanoparticles larger than 30 nanometers are not absorbed into our bodies through the skin. Particles smaller than 30 nanometers, on the other hand, can be absorbed through the skin and then enter our bloodstream. The effects these internally absorbed nanoparticles might have on our health is not yet known.”
Neither Titanium nor Titanium Dioxide has a role in human biosystems. Titanium dioxide contains titanium, a toxic heavy metal. Titanium dioxide creates more free radicals that do oxidative damage to your body and skin cells and increases aging processes.
Based on the experimental evidence from animal (rat) inhalation studies, titanium dioxide nanoparticles are classified as “possibly carcinogenic to humans” by the International Agency for Research on Cancer. Exposure to nano‐sized titanium dioxide also caused significant zooxanthellae expulsion in coral colonies. This expulsion leads to coral bleaching and possible death. However, non-nano titanium dioxide, similarly to non-nano zinc oxide, does not have the same effect on reefs, because its particles are large enough to not enter or interact with marine biosystems.
The best sunscreen active ingredient, for both human and marine biosystems, is non-nano zinc oxide, and by a wide margin. Non-nano titanium dioxide is a distant second-best choice, though it is less expensive than high-grade non-nano zinc oxide, and it is better than all petrochemicals. When using either ZnO or Ti2O, non-nano varieties are key. If a product uses non-nano, it will state this clearly within the ingredients; otherwise, it is almost assuredly NANO and should not be used. (Such products are marketed as “sheer” and “clear.”)
It’s vital to read sunscreen labels (not just the marketing messages) and understand the ingredients used in sunscreen and skincare products. (Remember, many sunscreen companies label their products as “reef-safe” simply because they don’t contain 2 specific petrochemical ingredients banned by a growing list of government jurisdictions, but they contain several other petrochemical ingredients that make them completely UNSAFE for reefs and other marine life. Always check the ingredients, know what those ingredients do, and decide for yourself.
1. Know your ingredients — Flip over your sunscreen and read the ingredients. We want everyone to know what good ingredients are, regardless of whether they use our products or not. Your health is worth it.
2. Buy safe sunscreen — Waxhead is dedicated to using only the healthiest, safest, most effective ingredients in our sunscreens. Shop Safe Sunscreen here.
3. Teach a friend — If you know someone who might still be buying sunscreen with questionable ingredients, please share this post with him/her.