Why to not mix Physical and Chemical SunscreensUpdated a year ago
It's not typically recommended to mix different types of sunscreens—physical (also known as mineral) and chemical—primarily due to the different ways in which they work to protect your skin from the sun's harmful ultraviolet (UV) rays.
- Mode of Action: Physical sunscreens work by sitting on top of the skin to deflect or scatter damaging UV rays away from the skin. They contain active mineral ingredients, such as titanium dioxide or zinc oxide. On the other hand, chemical sunscreens contain organic (carbon-based) compounds, such as oxybenzone, octinoxate, octisalate, and avobenzone, which create a chemical reaction and work by changing UV rays into heat, then releasing that heat from the skin. Combining them might interfere with the way they work.
- Compatibility: Not all ingredients in sunscreens are compatible. Certain ingredients in chemical sunscreens can destabilize others, reducing the effectiveness of the protection. This could potentially happen if you mix a physical and chemical sunscreen.
- Application: Because physical sunscreens work by forming a protective layer on the skin, applying a chemical sunscreen over the top of it may not be as effective, because the chemical sunscreen needs to be absorbed into the skin to work properly. Similarly, applying a physical sunscreen over a chemical one could wipe off the chemical sunscreen or reduce its effectiveness.