Both titanium dioxide and zinc oxide are used in the formulation of a specific variant of sunscreens. More specifically, these two mineral compounds represent one of the two categories of sunscreen formulation: physical sunscreens.
Note that chemical sunscreens are based on organic compounds that protect against sunlight by absorbing ultraviolet radiation. On the other hand, physical sunscreens use inorganic pigments that physically block UV radiation.
It is important to highlight the fact that titanium dioxide and zinc oxide are the only mineral compounds approved by the United States Food and Drug Administration and the European Medicines Agency for use as active ingredients in a physical sunscreen formulation.
The Difference Between Titanium Dioxide and Zinc Oxide in Terms of Providing Protection Against UV Radiation
Some consumers on the look for an ideal sunscreen product might come across the following questions: What is the difference between titanium dioxide and zinc oxide? Which one is better between the two? What are their respective benefits and specific applications?
Nevertheless, between the two, zinc oxide or ZnO is better than titanium dioxide because it provides broad-spectrum protection against both UVA rays and UVB rays. Note that these two subtypes of UV radiation have different effects on the skin and overall health.
Titanium dioxide or TiO2 is also effective against UVB rays but they are less effective against some short UVA or UVA II rays and completely ineffective against long UVA or UVA I rays.
Below are specific details in UV protection:
• Mode of Action: TiO2 and ZnO work primarily by reflecting or scattering UV rays so that they would not penetrate the skin. However, some studies suggest that ZnO also works by absorbing UV radiation and converting it to infrared heat.
• UV Spectrum: TiO2 protects against UV radiation with wavelengths ranging from 280-320nm or the entire UVB band and 320nm to around 340nm or the entire UVA II and some a little bit of UVA I band. ZnO works again UV radiation with wavelengths from 280-400nm or the entire UVB to UVA band.
• Stability: Nanoparticles of ZnO are highly stable under most conditions. The electrons remain intact when hit by a photon of ultraviolet. TiO2 are also generally stable but their electrons can go in a high-energy state when hit by UV rays, thus creating free radicals that can result in oxidative stress and damage.
• Cost: Zinc oxide is more expensive than titanium dioxide. Hence, sunscreens containing ZnO have higher price points than those containing TiO2. Other skincare products with SPF ratings usually contain TiO2 only in their formulation.
Note the following when choosing between TiO2 and ZnO:
The obvious choice between titanium dioxide and zinc oxide is the latter because it provides complete protection against the damaging effects of overexposure to UV radiation. Sunscreens made with 20 percent ZnO provides an SPF 32 rating plus broad-spectrum protection. In the United States, the FDA allows ZnO concentration of up to 25 percent.
Of course, because ZnO is more expensive to acquire, some manufacturers would include TiO2 in their formulations so that they could include an SPF rating in their labels. However, take note that an SPF rating only pertains to protection against UVB radiation. There are different rating and labeling standards for UVA protection.
Remember that a sunscreen formulation made only of TiO2 would not provide sufficient protection against UV radiation coming from the Sun. Although it protects against sunburns and other damages due to UVB rays, it does not provide protection against the specific harmful effects of UVA rays. Hence, it must be complemented with other ingredients.
There are also manufacturers that reduce the concentration of ZnO and complement the entire sunscreen formulation with TiO2 to bring down manufacturing costs. A formulation of at least 15 percent zinc oxide and at least 5 percent titanium dioxide can provide broad-spectrum protection with at least 35 percent SPF rating plus UVA protection rating.
Below are the similarities between titanium dioxide and zinc oxide:
TiO2 and ZnO are once called sunblocks because they physically block UV radiation. The U.S. FDA considers these two “Generally Recognized Safe and Effective” or GRASE. Studies have concluded that proper inclusions of these two ingredients in skincare product formulation, as well as their proper application, remain safe and effective. There have been concerns over the safety of organic chemicals used in chemical sunscreens.
However, because nanoparticles of TiO2 and ZnO are used in formulations, there are precautions against possible respiratory health risks. They are not ideal for use in water-based and spray-based sunscreen products because of potential for inhalation.
Another similarity between the two is that they are insoluble, unlike most chemical sunscreen ingredients. They are suitable for formulating products with some degree of water resistance, thus making them ideal for those involved in activities such as swimming or who perspire heavily with our without physical activity. It is important to note that “water-resistant” sunscreens are not “waterproof” and as such, they need to be reapplied frequently to remain protected.
For those concerned with the possible environmental impacts and potential health risks of using organic ultraviolet filters found in chemical sunscreen formulations, titanium dioxide and zinc oxide are considered the best alternatives.
Both ingredients also have other benefits. Studies have shown that TiO2 and ZnO have antimicrobial properties that can be used in the formulation of sanitizing skincare products. They are also ideal for sensitive skin because they pose a lower risk for allergic reactions compared to organic UV filters use in chemical sunscreens.
FURTHER READINGS AND REFERENCES
- American Academy of Dermatology. 2007. “At Common Usage Levels, Titanium Dioxide Is Not a Substitute for Avobenzone or Zinc Oxide for Broad-Spectrum Protection in Sunscreen Products.” Journal of the American Academy of Dermatology. 56(2): AB164. DOI: 1016/j.jaad.2006.10.754
- Schneider, S. L. and Lim, H. W. 2018. “A Review of Inorganic UV Filters Zinc Oxide and Titanium Dioxide.” Photodermatology, Photoimmunology & Photomedicine. 35(6): 442-446. DOI: 1111/phpp.12439
- Smijs, T. and Pavel, S. 2011. “Titanium Dioxide and Zinc Oxide Nanoparticles in Sunscreens: Focus on Their Safety and Effectiveness.” Nanotechnology Science and Applications. 4:95-112. DOI: 2147/nsa.s19419