How does sunscreen work?
Before we answer your question of if you should apply sunscreen before or after moisturizer to make the protection most effective, let’s first look into how sunscreen works.
Sunscreen is basically comprised of two categories of active ingredients– UV absorbers, i.e chemicals that absorb the UV rays and release the energy as low heat; and UV reflectors, i.e. mineral or physical particles, which reflects or scatters the UV rays from the skin.
So, going back to the question: “Sunscreen or moisturizer first?”, since chemical and physical sunblock works differently, the answer greatly depends on what kind of sunscreen you are using.
Chemical Sunscreen- Apply before moisturizer
As said, chemical sunscreen works by absorbing the ultraviolet rays from the sun, and convert the energy to almost unnoticeable low heat to release them. You may recall being told to put on your sunscreen 20-30 minutes before sun exposure, to activate the protection.
By activating the chemical sunscreen means to allow the particles to flow into the skin’s lines and ridges, and to bind properly to your skin to form a protective film. Your skin will also absorb the protective ingredients in the sunscreen during the time.
So you can imagine, if you applied a thick layer of moisturizer before the sunscreen, the moisturizer will create a barrier between you skin and the sunscreen, making the sunscreen unable to sink into your skin. The protection provided by the sunscreen would thus be weakened.
Therefore, it is advised to apply chemical sunscreen on bare skin first; then let it dry entirely on your skin before putting on moisturizer for optimal efficiency.
Physical Sunscreen- Apply after moisturizer & skincare
In contrast to how chemical sunscreen works by sinking into the skin, physical sunscreen that contains ingredients like titanium dioxide or zinc oxide works as physical block that sits on top of your skin to reflect away the UV rays.
Therefore, you can apply physical sunscreen as the last layer to create a physical barrier to protect your skin from the sun. And also, physical sunscreen works right away once applied on your skin, so there is no need to wait.
