Demystifying Sunscreens and SPF
SUNSCREEN
Sunscreen is a chemical agent that provides either a physical blocker or chemical filter from the suns ultraviolet radiation (UVR), thus providing some protection against sunburn.
The following terms are often used interchangeably: sun screen, sun block, sun tan lotion, sun cream or block out
Sunscreens can be in the form of a lotion, spray, gel or other topical product.
Sunscreens contain one or more of the following ingredients:
Depending on the mode of action sunscreens can be classified into:
Physical sunscreens (i.e., those that block and reflect the sunlight); or
Chemical sunscreens (i.e., those that filter and absorb the UV light).
Physical blockers
Sunscreens (often known as sun block ) containing physical blockers which often create a visible layer of sunscreen on skin. Typical ingredients are titanium dioxide and zinc oxide, which work in two ways:
1. Reflects the UVR as it reaches the skin.
2. Absorbs some UVR at a specific wavelength and converts it into heat energy.
Unlike the organic agents used in many sunscreens, these metal oxides do not degrade with exposure to sunlight.
Chemical filters
Chemical filters work by absorbing the UVR as it reaches your skin, and then counteracts the UVR to reduce damage.
Why use sunscreen?
Sunscreen helps to protect skin from harmful UVR and therefore reduce the risk of developing skin cancers (squamous cell carcinoma, basal cell carcinoma, melanoma) and skin damage (including premature ageing, solar keratoses and photodermatitis)
The level of protection afforded by sunscreen can vary due to factors including genetics, existing skin damage and skin type. For this reason sunscreen should not be regarded as the sole form of sun protection, but rather as the last line of defence against the suns harmful UV rays.
How to apply sunscreen
Sunscreen should be applied to clean, dry skin at least 20 minutes before going outside. This gives the protective elements in sunscreen time to bond to skin.
Apply according to directions on the product. Usually a large amount is not required (a rough guide suggests approximately one teaspoon per limb). The key factor is that the area is fully covered.
It is important to keep a thin film of sunscreen on your skin to maximise its effectiveness, so resist the temptation to rub it all in.
Sunscreen should be re-applied every two hours, or more frequently if you are sweating, swimming or it has been wiped or rubbed off.
What does SPF mean?
SPF stands for Sun Protection Factor, a laboratory measure of the effectiveness of sunscreen the higher the SPF, the more protection a sunscreen offers against UV-B (the ultraviolet radiation that causes sunburn).
Please note that (contrary to widespread belief) wearing SPF 15 does NOT mean that you can stay 15 times longer in the sun before getting burned.
Also doubling the SPF level does not indicate double protection. A sunscreen with an SPF 30+ rating only provides a small percentage increase in the amount of protection given by an SPF15+.
The guidelines for applying sunscreen do not change with the SPF rating.
SPF is not the sole determining factor of protection offered. In practice, the protection from a particular sunscreen depends on factors such as:
The SPF is an imperfect measure of skin damage because invisible damage and skin aging are also caused by ultraviolet type A (UVA) which does not cause reddening or pain.
Conventional sunscreen blocks very little UVA radiation relative to the nominal SPF; broad-spectrum sunscreens are designed to protect against both UVB and UVA.
UVA also causes DNA damage to cells deep within the skin, increasing the risk of malignant melanomas.
Even some products labeled "broad-spectrum UVA/UVB protection" do not provide good protection against UVA rays. The best UVA protection is provided by zinc oxide based physical blockers.
Owing to consumer confusion over the real degree and duration of protection offered, labeling restrictions are in force in many countries. In the European Union sunscreen labels can only go up to SPF 50+ (actually indicating a SPF of 60 or higher). In Australia the upper limit is 30+. The United States does not have mandatory, comprehensive sunscreen standards.
Which sunscreen should I use?
As noted above, many sunscreens do not block UVA radiation, which does not cause sunburn but can increase the rate of melanoma and photodermatitis, so people using sunscreens may be exposed to high UVA levels without realizing it.
The use of broad-spectrum (UVA/UVB) sunscreens can address this concern.
When choosing a sunscreen look for the following:
Sun Protection Factor (SPF) of 30+.
Broad spectrum (protects against UVA and UVB).
Water resistant.
Using an SPF30+ sunscreen means you are protected from approximately 96.7 per cent of UVR and getting a very good level of protection.
Price is not a good indicator regarding the suitability of a sunscreen product.
Water resistant sunscreen
Water resistant sunscreen contains ingredients to help continue to protect your skin when immersed in water. To ensure ongoing protection from these sunscreens, it is vital to reapply after swimming or perspiring, i.e. during sporting activities, outdoor work sites, swimming or gardening.
But what about my Vitamin D?
Its true that the use of sunscreen does interferes with vitamin D production.
Doctors recommend spending small amounts of time in the sun without sun protection to ensure adequate production of vitamin D
Daily conditions all year in tropical climates, or in spring and summer seasons in temperate regions are such that adequate amounts of vitamin D[SUB]3[/SUB] can be made in the skin after only ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen.
With longer exposure to UVB rays, an equilibrium is achieved in the skin, and the vitamin simply degrades as fast as it is generated.
Do sunscreens have a use by date?
Yes. Over time chemical components contained in sunscreen will break down, reducing the protection level indicated on the label. To maximise the life of your sunscreen (approximately three years), it is essential to store it in a cool place (below 30°C) and regularly check the expiry date if one is printed on the packaging.
Given the type of activities we are normally engaged in when sunscreen might be required its quite likely that your sunscreen isnt stored in ideal conditions (e.g. in a hot vehicle) so be aware of the consequences of that.
Additives to sunscreen
A number of sunscreens have substances to help the skin to darken or tan, however these additives do not provide additional protection from UV rays.
Cosmetics containing sunscreen
Many make-up and cosmetic products include an SPF rating on the label. This means that chemicals have been added to the base products to provide sun protection. These products are subject to the same testing procedures as any sunscreen; however it is important to note that some may not be broad spectrum or water resistant. Remember too that make-up and cosmetics are rarely reapplied every two hours.
Sunscreen and babies
Infants, particularly under the age of two years, should be kept out of the
sun as much as possible and should always be protected from any sun exposure by using a number of SunSmart behaviours including protective clothing, hats, and shade.
When these forms of sun protection are not adequate, sunscreen can be used. Sunscreen can be applied to the small areas of the skin which are not covered by clothing such as the face and back of the hands and neck.
There is no evidence to suggest that the use of sunscreen on infants and children is
harmful to their skin or has any adverse long-term side effects.
Always try new sunscreen on a small area of skin first to make sure there is no reaction. If your child does have a reaction, try using another variety of sunscreen with a different active ingredient.
How much protection is offered by clothing ?
The protections offered by clothing can also be expressed as SPF, as follows:
Nylon Stockings: SPF 2
Hats: SPF 3-6
Summer-weight clothing: SPF 6.5
Sun-protective clothing: up to SPF 30
Be SunSmart!
Dont rely on the sunscreen to protect your skin for extended periods of time. The use of sunscreen is recommended as an addition to the other SunSmart strategies.
Nor should you deliberately increase your amount of time in the sun because you have applied sunscreen.
For the best sun protection from the sun, ALWAYS:
1. Slip on protective clothing / swimwear.
2. Slop on SPF 30+sunscreen. Reapply every two hours.
3. Slap on a broad-brimmed hat.
4. Seek shade and limit exposure between 10am and 3pm.
5. Slide on wrap-around sunglasses.
Sources:
I have consulted the websites of, and material distributed by, the following organisations in the collation of this article. In some cases I have reproduced certain paragraphs in full (e.g. the SunSmart campaign from Australia). I am sure that their primary interest is in protecting people from sun damage and that they would have no objections to my doing so, however its important to note that the article as presented is not specifically endorsed by any of these organisations.
Thank you to: The Cancer Council of Queensland, American Cancer Society, Skin Cancer Foundation, Australian Government Department of Health and Ageing. US Food and Drug Administration, Wikipedia, Physics.org
Remember: Slip. Slop, Slap, Seek and Slide.
SUNSCREEN
Sunscreen is a chemical agent that provides either a physical blocker or chemical filter from the suns ultraviolet radiation (UVR), thus providing some protection against sunburn.
The following terms are often used interchangeably: sun screen, sun block, sun tan lotion, sun cream or block out
Sunscreens can be in the form of a lotion, spray, gel or other topical product.
Sunscreens contain one or more of the following ingredients:
- Organic chemical compounds that absorb ultraviolet light.
- Inorganic particulates that primarily reflect and scatter UV light (such as titanium oxide, zinc oxide) and also absorb some UVR.
- Organic particulates act mostly like organic chemical compounds in absorbing light but may reflect and scatter a fraction of light like inorganic particulates.
Depending on the mode of action sunscreens can be classified into:
Physical sunscreens (i.e., those that block and reflect the sunlight); or
Chemical sunscreens (i.e., those that filter and absorb the UV light).
Physical blockers
Sunscreens (often known as sun block ) containing physical blockers which often create a visible layer of sunscreen on skin. Typical ingredients are titanium dioxide and zinc oxide, which work in two ways:
1. Reflects the UVR as it reaches the skin.
2. Absorbs some UVR at a specific wavelength and converts it into heat energy.
Unlike the organic agents used in many sunscreens, these metal oxides do not degrade with exposure to sunlight.
Chemical filters
Chemical filters work by absorbing the UVR as it reaches your skin, and then counteracts the UVR to reduce damage.
Why use sunscreen?
Sunscreen helps to protect skin from harmful UVR and therefore reduce the risk of developing skin cancers (squamous cell carcinoma, basal cell carcinoma, melanoma) and skin damage (including premature ageing, solar keratoses and photodermatitis)
The level of protection afforded by sunscreen can vary due to factors including genetics, existing skin damage and skin type. For this reason sunscreen should not be regarded as the sole form of sun protection, but rather as the last line of defence against the suns harmful UV rays.
How to apply sunscreen
Sunscreen should be applied to clean, dry skin at least 20 minutes before going outside. This gives the protective elements in sunscreen time to bond to skin.
Apply according to directions on the product. Usually a large amount is not required (a rough guide suggests approximately one teaspoon per limb). The key factor is that the area is fully covered.
It is important to keep a thin film of sunscreen on your skin to maximise its effectiveness, so resist the temptation to rub it all in.
Sunscreen should be re-applied every two hours, or more frequently if you are sweating, swimming or it has been wiped or rubbed off.
What does SPF mean?
SPF stands for Sun Protection Factor, a laboratory measure of the effectiveness of sunscreen the higher the SPF, the more protection a sunscreen offers against UV-B (the ultraviolet radiation that causes sunburn).
Please note that (contrary to widespread belief) wearing SPF 15 does NOT mean that you can stay 15 times longer in the sun before getting burned.
Also doubling the SPF level does not indicate double protection. A sunscreen with an SPF 30+ rating only provides a small percentage increase in the amount of protection given by an SPF15+.
The guidelines for applying sunscreen do not change with the SPF rating.
SPF is not the sole determining factor of protection offered. In practice, the protection from a particular sunscreen depends on factors such as:
- The skin type of the user.
- The amount applied and frequency of re-application.
- Activities in which one engages (for example, swimming leads to a loss of sunscreen from the skin).
- Amount of sunscreen the skin has absorbed.
The SPF is an imperfect measure of skin damage because invisible damage and skin aging are also caused by ultraviolet type A (UVA) which does not cause reddening or pain.
Conventional sunscreen blocks very little UVA radiation relative to the nominal SPF; broad-spectrum sunscreens are designed to protect against both UVB and UVA.
UVA also causes DNA damage to cells deep within the skin, increasing the risk of malignant melanomas.
Even some products labeled "broad-spectrum UVA/UVB protection" do not provide good protection against UVA rays. The best UVA protection is provided by zinc oxide based physical blockers.
Owing to consumer confusion over the real degree and duration of protection offered, labeling restrictions are in force in many countries. In the European Union sunscreen labels can only go up to SPF 50+ (actually indicating a SPF of 60 or higher). In Australia the upper limit is 30+. The United States does not have mandatory, comprehensive sunscreen standards.
Which sunscreen should I use?
As noted above, many sunscreens do not block UVA radiation, which does not cause sunburn but can increase the rate of melanoma and photodermatitis, so people using sunscreens may be exposed to high UVA levels without realizing it.
The use of broad-spectrum (UVA/UVB) sunscreens can address this concern.
When choosing a sunscreen look for the following:
Sun Protection Factor (SPF) of 30+.
Broad spectrum (protects against UVA and UVB).
Water resistant.
Using an SPF30+ sunscreen means you are protected from approximately 96.7 per cent of UVR and getting a very good level of protection.
Price is not a good indicator regarding the suitability of a sunscreen product.
Water resistant sunscreen
Water resistant sunscreen contains ingredients to help continue to protect your skin when immersed in water. To ensure ongoing protection from these sunscreens, it is vital to reapply after swimming or perspiring, i.e. during sporting activities, outdoor work sites, swimming or gardening.
But what about my Vitamin D?
Its true that the use of sunscreen does interferes with vitamin D production.
Doctors recommend spending small amounts of time in the sun without sun protection to ensure adequate production of vitamin D
Daily conditions all year in tropical climates, or in spring and summer seasons in temperate regions are such that adequate amounts of vitamin D[SUB]3[/SUB] can be made in the skin after only ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen.
With longer exposure to UVB rays, an equilibrium is achieved in the skin, and the vitamin simply degrades as fast as it is generated.
Do sunscreens have a use by date?
Yes. Over time chemical components contained in sunscreen will break down, reducing the protection level indicated on the label. To maximise the life of your sunscreen (approximately three years), it is essential to store it in a cool place (below 30°C) and regularly check the expiry date if one is printed on the packaging.
Given the type of activities we are normally engaged in when sunscreen might be required its quite likely that your sunscreen isnt stored in ideal conditions (e.g. in a hot vehicle) so be aware of the consequences of that.
Additives to sunscreen
A number of sunscreens have substances to help the skin to darken or tan, however these additives do not provide additional protection from UV rays.
Cosmetics containing sunscreen
Many make-up and cosmetic products include an SPF rating on the label. This means that chemicals have been added to the base products to provide sun protection. These products are subject to the same testing procedures as any sunscreen; however it is important to note that some may not be broad spectrum or water resistant. Remember too that make-up and cosmetics are rarely reapplied every two hours.
Sunscreen and babies
Infants, particularly under the age of two years, should be kept out of the
sun as much as possible and should always be protected from any sun exposure by using a number of SunSmart behaviours including protective clothing, hats, and shade.
When these forms of sun protection are not adequate, sunscreen can be used. Sunscreen can be applied to the small areas of the skin which are not covered by clothing such as the face and back of the hands and neck.
There is no evidence to suggest that the use of sunscreen on infants and children is
harmful to their skin or has any adverse long-term side effects.
Always try new sunscreen on a small area of skin first to make sure there is no reaction. If your child does have a reaction, try using another variety of sunscreen with a different active ingredient.
How much protection is offered by clothing ?
The protections offered by clothing can also be expressed as SPF, as follows:
Nylon Stockings: SPF 2
Hats: SPF 3-6
Summer-weight clothing: SPF 6.5
Sun-protective clothing: up to SPF 30
Be SunSmart!
Dont rely on the sunscreen to protect your skin for extended periods of time. The use of sunscreen is recommended as an addition to the other SunSmart strategies.
Nor should you deliberately increase your amount of time in the sun because you have applied sunscreen.
For the best sun protection from the sun, ALWAYS:
1. Slip on protective clothing / swimwear.
2. Slop on SPF 30+sunscreen. Reapply every two hours.
3. Slap on a broad-brimmed hat.
4. Seek shade and limit exposure between 10am and 3pm.
5. Slide on wrap-around sunglasses.
Sources:
I have consulted the websites of, and material distributed by, the following organisations in the collation of this article. In some cases I have reproduced certain paragraphs in full (e.g. the SunSmart campaign from Australia). I am sure that their primary interest is in protecting people from sun damage and that they would have no objections to my doing so, however its important to note that the article as presented is not specifically endorsed by any of these organisations.
Thank you to: The Cancer Council of Queensland, American Cancer Society, Skin Cancer Foundation, Australian Government Department of Health and Ageing. US Food and Drug Administration, Wikipedia, Physics.org
Remember: Slip. Slop, Slap, Seek and Slide.
