Physical sunscreens protect your skin from the sun by deflecting or blocking the sun’s rays, while chemical sunscreens work by absorbing the sun’s rays. Some chemical filters can scatter sun rays, but still mostly just absorb them.
All sunscreens have an active ingredient (also known as a UV filter) that protects you from the sun.
Physical UV Filters:
- Titanium dioxide (TiO2)
- Zinc oxide (ZnO)
Chemical UV Filters:
- Mexoryl SX and XL
- Tinosorb S and M
- Uvinul T 150
- Uvinul A Plus
You want to choose a sunscreen which has active ingredients that are photostable, meaning they retain their stability upon exposure to sunlight and are unchanged. Physical UV filters are generally stable, however you do want to be careful when choosing a chemical sunscreen, as not all of them stay unaffected with sun exposure (avobenzone, for instance, is notoriously unstable).
All EltaMD sunscreens at NewDermaMed are formulated with zinc oxide, which is the most photostable sunscreen ingredient.
Many people with oilier, break out prone skin tend to stray away from using an SPF because they worry it may worsen their skin. Chemical filters tend to be more irritating to the skin, and in some cases, may even cause allergic reactions. Those with problematic skin will want to choose a sunscreen formulated with zinc oxide, as it is generally safe and can be used even on the most delicate skin. Titanium dioxide can cause problems for some people. If you break out from mineral makeup, it’s the titanium dioxide that could be the culprit.
Chemical filters generally offer more coverage against UVA and UVB rays than physical sunscreens, but the range of protection will depend on the photostability of its active ingredient. Because your skin needs to time to absorb chemicals, you need to wait 20 minutes post-application for effective sun protection.
Titanium dioxide protects against UVB rays, but not the full spectrum of UVA rays. Zinc oxide is the most photostable sunscreen ingredient, and protects against the entire spectrum of UVA and UVB rays. All physical sunscreens begin protecting you immediately upon application.
Physical sunscreens are thick and opaque, and can sometimes leave a white cast or tint on the skin. It can rub off more easily and must be frequently reapplied. Chemical sunscreens are colorless, odorless, and usually runny. They can even double as a makeup primer, depending on the active formulation.
All physical sunscreens have been deemed safe and are completely approved by the FDA. While chemical sunscreen are generally safe, some chemical filters can actually generate free radicals, which can cause skin damage, irritation, and even aging. Many chemical UV filters have not been approved by the FDA, but are commonly found in sunscreens sold in Europe and Asia.