physical vs chemical sunscreen

The Difference Between Physical and Chemical Sunscreen

September 18, 2018

In this post, discover the differences between physical vs. chemical sunscreen and the type of sunscreen we recommend.

Two Major Types: Physical vs. Chemical Sunscreen

We aren't talking brands here. There are literally dozens of different sunscreen makers. Instead, we’re discussing the two main "types" of sunscreen.  How sunscreens work depends on how they are formulated. Many popular, big-name brands rely on complex chemicals like Avobenzone to safeguard your skin from sun damage. When this type of sunscreen is applied to the skin and then exposed to the sun, a chemical reaction takes place. This reaction, in essence, absorbs the UV rays of the sun. 

For some people, this chemical reaction occurring on the skin’s surface can cause inflammation (and not just in those who are sensitive). In the office, these patients will frequently complain that sunscreen "breaks" them out. But what these people are actually experiencing is irritation dermatitis, not truly an acne-type of breakout. Steering these patients toward a simple physical sunscreen is usually the solution.  (Some makers will combine chemical and physical blocking agents, but people who tend to react to a chemical base will still have a problem with these combos.)

This brings us to my personal favorite type of sunscreen, what we call a "physical sunscreen". These products contain zinc oxide and titanium as the only active ingredients. When these minerals are applied to the skin, they form a layer that physically prevents the sun's UV rays from penetrating it (thus the name “physical sunscreen”). Oh, but zinc...that's what the lifeguards wore on their noses, right? Enter micronized zinc and the nano-particle.  

What Are Nano-Particles? 

A nano-particle is a particle smaller than 100 nanometers, or 100 billionths of a meter, and it is the particle size of the minerals in many current physical sunscreens. Historically, mineral-based products went on pretty thick. After all, their job was to form a protective coating on the skin. The reality is that nobody really wants to look like that. So over the years, advances have been made in the processing of zinc and titanium to make them smaller. The reason to make them smaller, of course, is so that they will absorb completely into the skin. As such, these products have become more aesthetically pleasing. So, what’s wrong with that? The problem with making these minerals smaller lies in the potential for these new nano-sized particles to be absorbed into the skin. 


Enter Non-Nano Sunscreen

Much debate has been brewing as to the validity of these concerns. To play it safe, we do not use nano-sized particles in our Mineral Shield Sunscreen. That means it will feel more like cream than lotion. Before applying it, give it a good shake, then take your time and rub it in well to blend. Sunscreen needs to be reapplied every couple of hours, and unless stated to be water resistant, should be reapplied after swimming or sweating.

Savy Guthrie has been a PA working in dermatology for 17 years and has worked in medicine for 20 years overall.  She has treated tens of thousands of patients, helping them achieve healthy, beautiful skin. 

Savy Guthrie is a dermatology PA with 17 years of patient care experience and is the founder of Theoderma Skin Care.

Savy with her dog

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