Physical blockers in sunscreen work like a shield on the surface of the skin to prevent absorption of damaging sun rays. Physical blockers are also thought to be more effective at blocking both UVA and UVB rays. These types of blockers also boast a longer shelf life and longer wear time on the skin, but are not as resistant to water and sweat like chemical blockers. When formulating with physical blockers here are some things to keep in mind.
Physical Blockers – Zinc Oxide vs. Titanium Dioxide
Zinc oxide and titanium dioxide are both well-known agents that can be used as sun-protectants. They prevent harmful radiation by physically blocking sunlight, unlike chemical sunscreens that only absorb the light and protect at a cellular level. Both these physical blockers protect against UVA and UVB radiation, but don’t perform at the same level. Titanium dioxide is a more stable ingredient and much more reflective than zinc oxide. However, zinc oxide has a lower opacity and provides safer sun protection. Most products often include both ingredients in their formulation to incorporate all the benefits of both ingredients.
Older zinc and titanium-based sunscreens have a relatively large particle size, making the product more opaque and leaving an unattractive white finish on the skin. Nowadays, zinc oxide and titanium dioxide sunscreens use micro particles, usually between 280 and 380 nanometers in diameter, to provide a more desirable transparent look. Zinc oxide tends to be less opaque than the same amount of titanium dioxide.
Keep this little factoids in mind when formulating your next SPF product!