Truth be told, I started writing this article thinking that I knew the clear differences between physical and chemical sunscreens and thought that with some proper references for clarity and proof, I’d be set. Unfortunately (or fortunately? Because learning is always great!), things never do go as planned. So here I am. Armed with some newfound knowledge from Stephen Alain Ko of KindofStephen and Michelle Wong of LabMuffin among others (references all linked below), let’s figure out the differences between physical and chemical sunscreens, as well as some common misconceptions many of us might’ve thought to be true!
BUT FIRST... WHY BOTHER WITH SUNSCREEN ANYWAY?
The short of it: sunscreen reduces your overall exposure to UV rays and hence, lowers your risk of skin cancer, sun damage and premature aging . In terms of UV rays, there are two known classifications – UVA and UVB. To make things simpler, just remember this:
|UVA = Aging||UVB = Burning|
|Causes fine lines, wrinkles and age spots that make skin look prematurely older.||Causes sunburn, as it penetrates the skin more superficially.|
|Has the ability to pass through glass, eg. while driving or sitting in front of windows with the curtains open.||Cannot pass through glass.|
|May cause skin cancer.||May cause skin cancer.|
↑ Table based on references  & .
So, the next time you think of ditching your sunscreen because you “don’t need it” or that you “only need it in the summer and/or at the beach”, just think of all the potential side-effects you could be dealing with, especially in the long term!
Now that that’s over with…
LET'S GET PHYSICAL!
Kicking things off with the first type of sun protection agent: physical sunscreen, or also more accurately known as mineral or inorganic sunscreen. However, I’ll refer to it as physical for the sake of brevity. Containing either titanium dioxide or zinc oxide (or both!) as their active ingredients, which are naturally occurring minerals and inorganic (not carbon-based), physical sunscreens are usually recommended for those with more sensitive or irritation-prone skin as they’re less likely to cause an allergic reaction. Though, of course, there are always outliers. In addition, zinc oxide and titanium dioxide are said to be non-comedogenic, generally pregnancy-safe, and broad-spectrum as they’re effective at blocking both UVA and UVB rays.
Now, how do physical sunscreens work? This is admittedly where it got tricky and eye-opening for me. Instead of the misconception that the mineral filters work by sitting on top of the skin to deflect and scatter damaging UV rays away from the skin , in reality, only about 5% of UVB light is reflected by physical sunscreens while the remainder is absorbed and converted into heat, similar to chemical sunscreens . I’ll just let that sink in…
In terms of disadvantages, the main drawback to physical sunscreens, especially for people of colour (POC), is probably the white cast that tends to form upon application, especially if the sunscreen in question contains titanium dioxide . Additionally, these sunscreens also tend to have a thick, greasy and chalky texture which is a general turn-off for most.
SO, WHAT'S MY OTHER OPTION?
Say hello to chemical sunscreen! Similar to their physical counterparts, these sunscreens contain organic (carbon-based) compounds which absorb the sun’s UV rays, creating a chemical reaction whereby UV rays are converted into heat which is then released from the skin . Examples of common chemical filters are oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate , though there are also newer filters such as Tinosorb S and M, and Uvinul A Plus. In chemical sunscreens, usually two to six of these active ingredients are used.
*Protip: to determine whether a sunscreen is physical or chemical filter-based, just check to see if they contain any physical blockers (ie. zinc oxide, titanium dioxide), and if they don’t, you’re probably looking at a chemical sunscreen! Though, there is an exception… just read until the end.
Now, unlike physical sunscreen, chemical sunscreens are more POC-friendly as they’re less likely to leave an obvious white cast. They’re also usually formulated to have thinner and fluid-like consistencies, which makes it more marketable to the general public. In terms of disadvantages, chemical sunscreens are often said to be unsuitable for sensitive skin due to a number of filters being common irritant and allergen, such as avobenzone (which is in almost all broad spectrum chemical sunscreens), octocrylene, oxybenzone, PABA, Padimate O and enzacamene . Some chemical filters are also said to be dangerous to use while pregnant or breastfeeding as they can be absorbed by the body.
WHAT IF I WANT THE BEST OF BOTH WORLDS?
Good news: there is such a thing as hybrid sunscreen. In this case, the sunscreen in question would contain filters from both physical and chemical to make up an often stable, cosmetically elegant formulation. For example, think of a sunscreen that’s white cast-free and safe for sensitive skin. Though, of course, YMMV (Your Mileage May Vary).
At the end of the day, as quoted from the American Academy of Dermatology, the best type of sunscreen is the one you will use again and again . Just be sure that it has an SPF of ≥30, offers broad-spectrum protection and even better if it’s water resistant!
REFERENCES / CREDITS: