When it comes to sunscreen formulation, two mineral UV filters consistently stand out for their safety, stability, and broad protective capabilities: Titanium dioxide (TiO₂) and Zinc oxide (ZnO). These ingredients are well-regarded not only by cosmetic chemists but also by global regulatory bodies for their reliability and safety profile—especially for individuals with sensitive skin or vulnerable skin conditions.
The US FDA has proposed two ingredients: zinc oxide (ZnO) and titanium dioxide (TiO2) to be safe and effective for sunscreen. TiO₂ and ZnO are common physical powder sunscreen agents known for their minimal skin absorption, thus ensuring a high level of safety. This is one of the primary reasons mineral sunscreens are preferred for babies, individuals with damaged skin barriers, and those who struggle with irritation from chemical filters.
TiO₂ exhibits exceptional stability, making it a reliable choice for sunscreen formulations. It is compatible with various organic sunscreen agents without undergoing any adverse reactions. Therefore, it is a compound that has been validated by the US FDA to be safe and non-irritating, non-allergenic and non-comedogenic to the skin. Its chemical inertness and lack of photoreactivity make it especially suitable for individuals with sensitive skin, fragile skin conditions as well as children.
How TiO₂ and ZnO Protect the Skin
Modern photoprotection science examines how different UV filters behave across the UV spectrum. This includes both:
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UVB (280–320 nm) — the primary cause of sunburn
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UVA (320–400 nm) — responsible for deeper skin damage, ageing, sagging, and pigmentation
The sun protection efficacy has been investigated, as depicted in
Figure 1. TiO₂ demonstrates superior protection against UVB (280-320 nm) rays, whereas ZnO exhibits greater effectiveness in shielding against UVA (320-400 nm) rays, with a peak ultraviolet filtering wavelength of approximately 370 nm.
This complementary behavior is the foundation of a well-balanced mineral sunscreen.
How to Choose the Right Sunscreen
With so many sunscreen labels and claims in the market, understanding what matters most can guide consumers toward safer and more effective choices.
US FDA proposed sunscreen requirement in 2019, consumers should use broad spectrum sunscreens with sun protection factor (SPF) 15 and higher regularly (Table 1). Broad spectrum sunscreens with SPF 15 and higher protect against UVA and UVB rays, can reduce the risk of skin cancer and early ageing when used with other protection measures.
Table 1: SPF Value and Its Protection Level
| Sun Protection Factor (SPF) | UV Radiation (UVR) Admission | Protection Level |
|---|---|---|
| 15 | Admits 1/15th of the ambient UVR. | 93% UVB |
| 30 | Admits 1/30th of the ambient UVR. | 96.7% UVB |
| 50 | Admits 1/50th of the ambient UVR. | 98.3% UVB |
Source: FDA Sun Protection Factor
Understanding the PA System
Because SPF measures UVB protection only, consumers also need guidance on UVA protection. For that, Japan introduced the PA Index.
Meanwhile, Japan Cosmetic Industry Association (JCIA) introduced the PA index to measure sunscreen’s UVA blocking ability. PA index stands for Protection Grade of UVA and the guidelines as shown in Table 2.
Table 2: Photoprotection Grades According to JCIA Guidelines
| Photoprotection Factor of UVA Value | Protection Grade (PA) | Protection Level |
|---|---|---|
| 2 or more, but less than 4 | PA+ | Low |
| 4 or more, but less than 8 | PA++ | Moderate |
| 8 or more, but less than 16 | PA+++ | High |
| 16 or more | PA++++ | Extremely high |
Source: JCIA / persistent pigment darkening protocol
Putting It All Together: SPF vs PA
Overall, higher SPF protects against UVB rays and higher PA protects from UVA. It is crucial to consider activities and skin type when choosing sunscreen products.
For venturing outdoors, it is recommended to choose sunscreen with PA++ or PA+++ and SPF 30 and above as it can block about 97% of UVB rays.
Written By: Dr. Tan Kian Meng, PhD in Engineering Technology (UTHM)
