Dr Ian Webster
Dr Ian Webster

The Difference between Chemical & Physical Sunscreens

It can be overwhelming trying to choose the right sunscreen when confronted by so many choices, not to mention all the terminology: SPF, broad-spectrum, micronized, physical, mineral, chemical, organic, inorganic …

When it comes to sunscreens there are essentially two distinct types of sunscreens that refer to the type of UV filters that are used. These are namely Chemical and Physical and then there is another third category for formulations that are a blend of these two types of sunscreen.

Some chemists prefer to use the terms Organic UV filters ie. chemical compounds that contain a carbon atom, vs inorganic UV filters which are inert physical compounds and do not contain a carbon atom. We find this can be information overload to the general public – so we’ll just stick to Chemical vs. Physical for the purposes of this article.

Chemical Sunscreens

Chemical sunscreens mostly absorb ultraviolet radiation and release their energy in a harmless way. They are generally easy-to-use and absorb into the skin quickly and efficiently as modern formulations not only protect but moisturise the skin. Some recent studies have indicated that chemical UV filters also reflect a small percentage of light, so we can’t definitively say they exclusively absorb UV radiation, but for the most part, this is what they do.

A small percentage of people may become allergic to chemical sunscreens especially with the older formulations that contained Para-AminoBenzoic Acid (PABA) but these are hardly used today. With regard to photostability in chemical sunscreens, this can depend on the particular chemicals used in the formulation.

Chemical sunscreens provide good protection against both UVA and UVB but during the absorption process the chemicals can be broken down by the sun and this is why it is important to re-apply sunscreen regularly throughout the day. More modern sunscreens contain antioxidants which provide an extra layer of protection to the skin.

When applying a chemical sunscreen you should wait at least 20 minutes to allow it to absorb fully before sun exposure.

Damage to Coral Reefs

Some recent studies have indicated that some chemical/organic sunscreens like Oxybenzone can be damaging to coral reefs. Based on further reading on this topic, it can be said one should be cautious of swimming near a coral reef, in large numbers of people using chemical sunscreens – otherwise, the impact of swimming in an ocean thousands of kilometers from a coral reef has not been firmly established. There are also too many other more important environmental factors deserving of our attention that are undoubtedly contributing to coral bleaching. The biggest one of course being CO2 emissions and rising global temperatures which is causing ocean temperatures to increase. Some coral experts have indicated sunscreens sit around 200th on the list of issues causing coral bleaching, so our advice is to be mindful of the issue but also be aware there are are other more impactful ways one can help.

Physical Sunscreens

Physical sunscreens contain Zinc Oxide, or Titanium Dioxide – inert metals that sit on top of the skin and reflect harmful ultraviolet rays away from the skin. They are often referred to as sunblocks although sunscreens and sunblocks are one and the same thing.

For a long time, physical sunscreens were not as popular as chemical sunscreens because of the thick white, pasty film they left on the skin. However with modern technology, new physical formulations have been micronized by grinding larger particle sizes into smaller sizes that do not leave a white residue on the skin, so they are more cosmetically acceptable.

As Zinc Oxide and Titanium Dioxide are inert metals it is impossible to develop an allergic reaction to them. Titanium Dioxide can, however, cause breakouts in acne-prone skins.

Titanium Dioxide protects against UVB rays but not the full spectrum of UVA rays while Zinc Oxide protects against the entire spectrum of UVB and UVA rays. Physical sunscreens are all photostable.

Physical sunscreens go to work as soon as you apply them and give immediate protection – you do not have to wait before sun exposure. As they sit on top of the skin they do have a tendency to rub off more easily when towel drying but as with chemical sunscreens, it is always advisable to re-apply your sunscreen regularly throughout the day and especially after swimming or heavy sweating.

A new innovative sunscreen is a mineral sunscreen powder that is perfect for re-application during the day. It is compact and can be carried in your handbag or sports bag. Women like the fact that it does not interfere with their makeup when applied during the day due to the powder formulation.

Chemical & Physical Sunscreen Combination (Mixed UV Filters)

More modern sunscreens make use of both chemical and physical sun filters covering a far broader spectrum of UV radiation and other environmental aggressors that can cause skin ageing and skin cancer.

OTHER INTERESTING SUNSCREEN FACTS

  • These days there are more sunscreens formulated especially for the delicate eye area coming onto the market and these are indicated for people with eye sensitivity or who wear contact lenses. They are also indicated for sportspeople as they do not run into the eyes and cause stinging.
  • The SPF factor in sunscreen is worked out on people under perfect laboratory conditions. This is very different from real life and research has shown that we often do not apply our sunscreen thickly enough and we leave gaps when applying over a large area.
  • It has recently been shown that visible light may be harmful to the skin and therefore some of the more modern sunscreens, both chemical and physical, include Iron Oxide in their formulations. Iron oxide produces a slightly brown tint but this provides visible light protection. These are referred to as tinted sunscreens.
  • Fortunately, the modern sunscreens have many different formulations with or without tints and these days you can choose a sunscreen that is appropriate for your skin type. If you have an oily, acne-prone skin you should rather use an oil-free gel with a dry touch, matte finish. You should use a rich, cream-based sunscreen if you have dry skin and a lotion if you have a normal or combination skin.
  • My recommendation as a Dermatologist is to rather err on the side of a slightly higher SPF factor but what is most important is to have a sunscreen that has broad-spectrum protection against UVA as well as UVB radiation.
  • When it comes to choosing a sunscreen for yourself, it is a personal preference, taking skin type, lifestyle, and aesthetics into consideration. If your skin is sensitive a physical sunscreen would be best suited to your skin type. If you are sporty you would look for a sunscreen that does not run into your eyes when you sweat and for many, the choice of sunscreen depends on how comfortable it feels on their skin.

Sunscreens are an essential part of our lives but especially for those of us living under the glare of the harsh African sun. The sun is still a threat on overcast days even when you cannot see it so applying sunscreen is just as important these days. Protecting your skin can help to prevent skin ageing and more importantly skin cancer. No matter what your skin type, even if you do not burn when exposed to the sun, UV radiation can still cause DNA damage that leads to skin cancer.

Posted in LEARN / SUN PROTECTION on October 6th, 2016.

Leading Scientific Sunscreens

Colorescience Sunforgettable Total Protection Brush-On Shield SPF 50 (Fair)

Colorescience
Sunforgettable Total Protection Brush-On Shield SPF 50 (Fair)

R1,390.00

Colorescience
Sunforgettable Total Protection Brush-On Shield SPF 50 (Fair)

Mineral Make-Up with SPF.

All Skin Types

R1,390.00
Add View
SkinCeuticals Physical Fusion UV Defense SPF 50

SkinCeuticals
Physical Fusion UV Defense SPF 50

R660.00

SkinCeuticals
Physical Fusion UV Defense SPF 50

Tinted, Pure Mineral SPF

All Skin Types

 

R660.00
Add View

New to Active Ingredients?

We’d like to understand your Skin Type better!

If this is your first time buying Dermastore Active Ingredient products, we’ll need you to complete Dr Webster’s Facial Skin Assessment for Anti-Ageing, it’s free and takes just 45 seconds!

Get Started Now

Alternatively, if you’ve filled in our Assessment before, please login to continue.

X
Logout