Calvert Creak
Skin Care Information
Understanding Sunscreens
Thanks to extensive public education campaigns, most of us are aware of the dangers of excessive sun exposure. Apart from covering our skin with clothing or staying in the shade so that the sun’s rays do not reach you, the obvious choice for protecting against the sun’s damaging effects is the use of sunscreen. But not all sunscreens are created equal.
Different active sunscreen ingredients screen out different wavelengths of the sun’s ultraviolet (UV) radiation. There are three main UV wavelengths:
UV-A
- UV-A has the longest of the three UV wavelengths.
- The intensity of UV-A is high throughout the day (ie. it is no stronger at midday than at sunrise).
- The intensity of UV-A is similar from season to season (ie. it is almost as intense in Winter as in Summer).
- The intensity of UV-A is similar in all parts of the world (ie. it is as intense at the South Pole as the equator).
- UV-A penetrates the skin’s epidermis, dermis and subcutaneous tissue layer (ie. it penetrates the the deepest layer of the skin).
- UV-A is able to penetrate through glass (eg. through car windscreens) and plastic.
- UV-A was once thought to be safe but is now known to be a major contributor to skin ageing.
UV-B
- UV-B is in the mid-range of UV wavelengths.
- The intensity of UV-B is highest between 10 am and 2 pm.
- The intensity of UV-B is reduced in Winter months and highest in Summer months.
- The intensity of UV-B is highest around the Equator and lowest around the North and South Poles.
- UV-B is able to the penetrate the epidermal and dermal layers (but not the subcutaneous tissue layer) of the skin.
- UV-B is unable to penetrate glass or plastic.
- UV-B is the cause of sunburn.
- UV-B is responsible for tanning.
- UV-B is a cause of skin cancer.
UV-C
- UV-C is the shortest of the UV wavelengths.
- Most UV-C is absorbed by the earth’s ozone layer (however the hole in the ozone layer is increasing, which means that the southern regions of Australia are increasingly receiving more UV-C).
- UV-C is absorbed in the epidermal layer of the skin.
- UV-C is a cause of skin cancer.
Therefore all three spectrums of UV are toxic to the skin and should be protected against.
Types of Sunscreen
There are two classes of sunscreens – chemical sunscreens and physical sunscreens and within each class there are several active chemicals.
Chemical sunscreens deactivate the UV radiation that reaches the skin, thereby preventing the damage caused by the UV. Depending on the actual chemical, chemical sunscreens block varying portions of the UV-A, UV-B or UV-C spectrums.
Physical sunscreens (sometimes known as sunblocks) work differently. They act as a physical shield between the skin and sunlight.
Sun Protection Factor (SPF)
The SPF (Sun Protection Factor) rating on sunscreens is an indication of how many times longer it takes before the sun begins to cause reddening/sunburn after the sunscreen is applied. For example, an SPF of 30+ would theoretically allow you to remain in the sun for 30 times longer than if you were in the sun without protection.
Regardless of whether you use a chemical or physical sunscreen, it should have a minimum SPF of 15 for routine exposure or an SPF of 30+ during periods of intensive sun exposure.
Active Sunscreen/Sunblock Ingredients
The following list illustrates the differences in the protection provided by the different active ingredients in sunscreens:
Class |
Name |
UV Bands |
Protection (nm) |
Chemical Sunscreens |
|||
| Aminobenzoic Acids: | PABA |
UV-B (partial) |
260 – 313 |
Glyceryl PABA |
UV-B (partial) |
264 – 315 |
|
Padimate |
UV-B (partial) |
290 – 315 |
|
Roxadimate |
UV-B (partial) |
280 – 330 |
|
| Anthranilates: | Menthyl Anthranilate |
UV-A (partial) |
260 –380 |
Benzophenones: |
Dioxybenzone |
UV-A (partial) |
250 –390 |
Oxybenzone |
UV-A (partial) |
270 – 350 |
|
Sulisobenzone |
UV-A (partial) |
260 –375 |
|
Camphor Derivatives: |
Benzoate-4 methylbenzylidene camphor |
UV-B (partial) |
290 –300 |
Mexoryl SX |
UV-A (total) |
290 – 400 |
|
Cinnamates: |
Octocrylene |
UV-A (partial) |
250 – 360 |
Octyl Methoxycinnamate |
|
|
|
Dibenzoylmethanes: |
Avobenzone |
UV-A (total) |
320 – 400 |
Salicylates: |
Homosalate |
UV-B (partial) |
295 – 315 |
Octyl Salicylate |
UV-B (partial) |
280 – 320 |
|
Trolamine Salicylate |
UV-B (partial) |
260 – 320 |
|
Other: |
Phenylbenzimidazole |
UV-A (partial) |
290 – 340 |
Physical Suncreens: |
|||
Titanium Dioxide |
UV-A (total) |
290 – 700 |
|
Zinc Oxide |
UV-A (total) |
290 – 700 |
|
The Best Sunscreen of All?
If you want to obtain the best protection possible from a sunscreen lotion or cream, consider this advice. Recent studies indicate that you should aim to block out UV-A, UV-B, and UV-C. UV-C was once regarded as unimportant as the ozone layer of the atmosphere normally screens this wavelength of UV out for you before it can reach your skin. It is now widely-known that the ozone layer is becoming increasingly depleted from the earth's atmosphere because of greenhouse gas emissions.
Most first-generation sunscreens block out either UV-A or UV-B but not UV-C. Obviously these ingredients leave you open to the damage caused by the two spectrums of light that they are inoperative for.
Titanium dioxide is a physical sunscreen (sunblock). It blocks out UV-A and UB-V, but not UV-C. This ingredient is now one of the most common ingredients in sunscreens. The disadvantage of this ingredient (until recently) was that it was opaque (not clear) and was therefore shunned by many people because of its cosmetic unsuitability. Recently, a new process named micronisation, allowed the titanium dioxide particles to be broken down so that they became invisible when applied to the skin. Micronised titanium dioxide was therefore an "almost-perfect" solution for blocking out most of the sun's rays.
Recently it has been found that the use of titanium dioxide-containing sunscreens may be causing as many problems as they're helping solve. A study showed that micronised titanium dioxide may catalyse DNA damage in skin cells. Titanium dioxide absorbs 70% of UV and in watery environments this leads to the generation of hydroxyl free radicals which initiate oxidation and lead to the skin damage that initiates cancer. Obviously this is not what you want to occur.
So what's the answer? What's the very best sun protection this summer? Although it has not yet been very well publicised, micronised zinc oxide (also known as microfine zinc oxide) appears to be the ultimate sunscreen ingredient. Here's why:
- Micronised (microfine) zinc oxide is less white (in appearance on the skin) compared with non-micronised zinc oxide (the type of zinc oxide once seen widely on the noses of surfers and lifesavers) or micronised titanium dioxide.
- Micronised zinc oxide (unlike micronised titanium dioxide) does not cause DNA damage to the skin.
- Micronised zinc oxide protects against all of the UV-A spectrum of UV (micronised titanium dioxide only protects against part of the UV-A spectrum).
- Micronised zinc oxide protects against UV-B. This protection is as good as that provided by other sunscreens.
- Micronised zinc oxide (unlike titanium dioxide and most sunscreens) protects against UV-C.
- Micronised zinc oxide (unlike most sunscreens) does NOT cause allergic skin reactions.
