Physical vs. Chemical Sunscreen
The difference between physical and chemical sunscreens |
There are two general types of sunscreens, physical and chemical ones. Physical sunscreens use physical UV filters, while chemical sunscreens use chemical UV filters. There are also hybrid sunscreens that contain both physical and chemical sunscreen actives.
The differences between physical and chemical sunscreens are explained in the table below:
|How They Work||Physical sunscreens protect your skin from the sun by deflecting or blocking the sun's rays.||Chemical sunscreens work by absorbing the sun's rays. Some chemical filters can scatter sun rays, but still mostly just absorb them.|
|Other Names||Sunblock; Inorganic sunscreen||Organic sunscreen|
(UV filters are the active ingredient in sunscreens that protects you from the sun.)
For more information about UV filters, their description, and other sunscreen active ingredients check here.
|Stability||Generally stable||Most are photostable, but some are not.
Avobenzone is notoriously unstable. However, it can be stabilized when formulated in conjunction with other UV filters.
|Comedogenicity||Titanium dioxide can be problematic for some people. (If you break out from mineral make up and physical sunscreen, titanium dioxide could be the culprit.)
Zinc oxide is generally safe. It can be used on delicate skin and is a main ingredient in diaper rash cream.
|Chemical filters tend to be more irritating to skin.
If it gets in your eyes, it can make your eyes sting and water.
Some can cause allergic reactions.
How much protection is offered depends on the amount of the active ingredient in the sunscreen, particle size of the UV filters, photostability, and overall product formulation.
Titanium dioxide protects against UVB rays, but not the full spectrum of UVA rays.
Zinc oxide protects against the entire spectrum of UVB and UVA rays.
Starts protecting immediately upon application.
|Chemical filters offer more coverage against UVA and UVB rays than physical sunscreens, but the range of protection will depend on the particular active and its stability.
Avobenzone, for example, protects against the full spectrum UVA rays.
Must wait 20 minutes after application for effective sun protection.
|Texture||Thick and opaque, may be hard to apply.
Tends to leave a white cast or tint.
Rubs off more easily and must be frequently reapplied.
|Colorless, odorless, usually runny.|
Can sometimes double as a makeup primer, depending on the active and the formulation.
|Safety||Pretty safe, FDA approved.
Don't cause free radicals.
Note: Nanoparticle zinc oxide and titanium dioxide are controversial at the moment.
|Generally safe, however some chemical filters generate free radicals which can cause skin damage, irritation, and aging. |
Many chemical UV filters have not been FDA approved in the States, but are in sunscreens sold in Europe and Asia.
Physical sunscreens tend to be better tolerated by most skin types because the chemical filters used in chemical sunscreens can be irritating for many people. However, physical sunscreens tend to leave a white cast or white streaks after application and don’t offer as much UVA protection compared to chemical sunscreens. Physical sunscreens are also a bit thicker so they may be more difficult to apply. Since they each have their pros and cons, many of today's sunscreens contain both physical and chemical UV filters.
However, knowing whether a sunscreen is physical, chemical, or both does not tell you enough information about whether a particular sunscreen will be a good, protective one. Did you know that moisturizer or makeup with SPF doesn't offer adequate sun protection? Do you know the PPD of your sunscreen and how it can prevent your skin from aging? Do you apply enough sunscreen to your skin?
To answer these questions and learn more about how to choose a good sunscreen, go here.
Last updated: September 11, 2012