Sunblock vs. Sunscreen: What's the difference?

It’s almost August, the heart of the summer, so let’s talk about sun protection!  Sun protection is a well-covered topic, so I’ll skip what SPF means and get right to a commonly misunderstood element of sun protection – sunscreen vs sunblock.  

I’ve found almost every patient I educate on the topic of sunscreen vs sunblock did not understand the nuances of the two, and the saying “the devil is in the details” applies here as well.  This may sound a bit harsh referencing the devil in these details, but the sun, sunscreen, acne, and skin reactions can be harsh (and hot).

Chemical Sunscreens chemically alter the sun’s UVA/UVB rays.  This chemical reaction occurs in the pores, or on the surface of the skin.  Have you ever noticed a flush, heating, or redness when you’ve applied a chemical sunscreen?  This can be a skin sensitivity reaction or heat generated by the chemical reaction of the chemical sunscreen reacting with the sun’s rays.  

Wow.  The pros of this type of sun protection are these are much more water resistant and have more staying power than the mineral sunscreens.  The cons of chemical sunscreens involve skin allergies, skin reactions, skin irritation, acne breakouts, and even certain chemical sunscreens being thought to cause cancer and hormone disruption.  

I typically do not recommend chemical sunscreens ever for the face and recommend them on a limited basis for the body.  I see the utility for the body when swimming all day at a pool or beach.  These typically offer higher SPFs, and more time can pass between applications without burning.  Examples of common chemical sunscreens are: avobenzone, oxybenzone, oxtinoxate, homosalate, octisalate, octocrylene.  

Physical sunscreens are true sunblock.  They are minerals suspended in a cream or lotion.  There are two main players in the mineral sunblock world – titanium dioxide and zinc oxide.  These minerals sit on top of skin, and therefore are not getting into your actual pore.  This makes them far superior for sensitive skin or skin prone to acne breakouts.  

The minerals sitting on top of the skin act as a physical barrier to the sun, literally blocking or reflecting the sun’s rays away from touching your skin.  The cons of physical sunblocks are having to reapply more frequently, less water resistance since they are sitting on top of skin, and historically they have left that white “zinc” cast on skin.  

We currently sell LaRoche-Posay’s tinted mineral sunblocks, both liquid and primer, and they are fabulous, and do not leave a white cast to the skin.  In fact, these mineral sunblocks can double as a primer or a light foundation all while getting SPF of 50, and not flaring sensitive skin!