Sunscreen: a must read
Sunscreen comes in more varieties than Heinz sauce’s. How is one to navigate the aisles and aisles of different choices and pick the right sunscreen? This quick article will help you understand UV light, sunscreen ingredients and labeling so you will be able to make the right choice for you and your family members in any sunny situation.
About UV Light
To understand sunscreens first you must understand a little about the light they are designed to filter. UV or ultraviolet light is a very short and high energy electromagnetic wave that is produced by the sun. UV light can cause changes in DNA over time leading to collagen breakdown, sun spots and cancer. Three different UV rays make it to our planet: A, B and C. UVC rays are the shortest (100-280nm) and do not affect us much because they are mostly absorbed by the upper atmosphere. UVB rays are medium size (280-315nm) and UVA rays are the longest (315-400nm). Ordinary window glass passes about 90% of the light above 350 nm (UVA), but blocks over 90% of the light below 300 nm (UVB). UV light is not all bad, UVA can be used to fight certain skin conditions such as psoriasis and vitiligo and UVB helps make Vitamin D in the skin. However, too much UV light can damage DNA leading to certain types of skin cancers, mainly Basal Cell Carcinoma and Squamous Cell Carcinoma. UVB tends to cause direct DNA damage leading to sunburns and the above mentioned cancers. Although UVB light can be a factor in melanoma, about 92% of melanoma is caused by the indirect DNA damage i.e. free radicals and oxidative stress. UVA can contribute to skin cancer via this method of indirect DNA damage. It penetrates deeply but it does not cause sunburn. UVA does not damage DNA directly like UVB and UVC, but it can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. Because it does not cause reddening of the skin it cannot be measured in the SPF testing.
SPF
According to the FDA, there is no difference in products labeled sunscreen vs. sunblock. Currently, SPF is the most standardized measure on the bottle. SPF stands for Sun Protection Factor and is an overall laboratory measure of the product effectiveness against UVB radiation only. It is an indication of the time a person can be exposed to sunlight before getting sunburned with a sunscreen applied relative to the time they can be exposed without sunscreen. For example, if someone who would burn after 20 minutes in the sun applied a sunscreen with SPF 15, it would take approximately 5 hours (300 minute) for them to burn. However, skin type, application, and activities all effect how long a sunscreen actually lasts. The main problem in this measurement system is that SPF gives no indication as to the amount of UVA protection. Even if a product has an SPF of 100 it may have absolutely no protective effect against UVA radiation. According to a 2003 study, sunscreens with an SPF of 30+ may actually have less protection against UVA. In the future you may see sunscreens in the US labeled with Persistent Pigment Darkening (PPD). This method is currently used in the EU for measuring UVA protection in a similar way that SPF measures UVB protection. Theoretically, a sunscreen with a PPD rating of 10 should allow you to endure 10 times as much UVA as you would without protection. The PPD should be at least 1/3 of the SPF to carry the UVA seal which will become more common in the US over the next couple of years.
Physical vs. Chemical Sunscreen
Physical sunscreens such as zinc oxide, titanium dioxide and iron oxide have a few distinct advantages over their chemical counterparts. First they work as soon as you put them on, they do not require the 30 minutes of absorption time necessary that chemical sunscreens need to work properly. Chemical sunscreens tend to release free radicals. When a chemical sunscreen receives UV energy it normally converts it into a chemical reaction sometimes leading to the formation of free radical. Although no data has conclusively linked chemical sunscreen with a specific type of cancer there is data that shows a higher melanoma rate in countries that use high amounts of chemical sunscreen1-2. Some chemical sunscreen ingredients (benzophenone-3, homosalate, 4-methyl-benzylidene camphor (4-MBC), octyl-methoxycinnamate and octyl-dimethyl-PABA) may act like an estrogen type of hormone after being absorbed, promoting endometriosis in women and decreased libido in men. There may also be a link between breast cancer and the increased use of chemical sunscreens3.
Full Spectrum
Now many products are labeled with the words, “Full Spectrum.” This means that the manufacturer claims the product will cover both UVA and UVB radiation. Although this gives a better indication about the coverage of the product there is no FDA standard as to what “Full Spectrum” means so virtually any manufacturer can put it on their bottle. In general it is better to look at the active ingredients and see Zinc Oxide or Titanium Dioxide, as both cover UVA and UVB.
Marketing Madness
The manufacturers of ingredients such as Mexoryl (Ecamsule), which is seen in products like Helioplex and Anthelios, have done a very good job of confusing the public. LaRoche and Neutrogena have both spent millions to convince the public and some doctors that this chemical sunscreen works better than the ones we have had around for 50 years. Mexoryl does cover a better range of UVA than do most chemical sunscreens and tends to stand up better to UVA over time than its predecessor avobenzone (Parsol 1789). However, products like Anthelios (which is actually a combination of Octocrylene, Mexoryl and Avobenzone) are still no more effective than the simple mixture of zinc oxide and titanium dioxide.
What to do?
Despite all the controversy most doctors would agree that sunscreen helps prevent photodamage and may help reduce the risk of certain types of skin cancer. Physical blocks are probably safer and more effective than chemical blocks. Use sunscreen over the face, neck and back of hands but do not be afraid to let the rest of your body get a little sun as it was designed to do. Use sunscreen on your face every day especially if you have Melasma (even on cloudy days 70% of UV light makes it to the ground). If you are doing outdoor activities apply about every 2-4 hours. If you are in the water, even with a water resistant sunscreen, reapply when you get out. In the end the most important ingredients in a sunscreen are Zinc Oxide and Titanium Dioxide. Titanium dioxide’s peak absorption is in the 290-340 range and Zinc’s peak absorption is in the 340-380 range. This combination is both safe for long term use and very effective in limiting solar skin damage from UVA and UVB. Brands like SkinCeuticals, which can be purchased in many doctor’s offices, use pure ingredients like micronized zinc which make them more cosmetically elegant, less likely to cause irritation and easy to use. Our favorite for adults, pregnant adults and kids alike is SkinCeuticals Physical Defense SPF 30, active ingredients: Zinc Oxide and Titanium Dioxide. by - David M. Verebelyi, MD
About UV Light
To understand sunscreens first you must understand a little about the light they are designed to filter. UV or ultraviolet light is a very short and high energy electromagnetic wave that is produced by the sun. UV light can cause changes in DNA over time leading to collagen breakdown, sun spots and cancer. Three different UV rays make it to our planet: A, B and C. UVC rays are the shortest (100-280nm) and do not affect us much because they are mostly absorbed by the upper atmosphere. UVB rays are medium size (280-315nm) and UVA rays are the longest (315-400nm). Ordinary window glass passes about 90% of the light above 350 nm (UVA), but blocks over 90% of the light below 300 nm (UVB). UV light is not all bad, UVA can be used to fight certain skin conditions such as psoriasis and vitiligo and UVB helps make Vitamin D in the skin. However, too much UV light can damage DNA leading to certain types of skin cancers, mainly Basal Cell Carcinoma and Squamous Cell Carcinoma. UVB tends to cause direct DNA damage leading to sunburns and the above mentioned cancers. Although UVB light can be a factor in melanoma, about 92% of melanoma is caused by the indirect DNA damage i.e. free radicals and oxidative stress. UVA can contribute to skin cancer via this method of indirect DNA damage. It penetrates deeply but it does not cause sunburn. UVA does not damage DNA directly like UVB and UVC, but it can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. Because it does not cause reddening of the skin it cannot be measured in the SPF testing.
SPF
According to the FDA, there is no difference in products labeled sunscreen vs. sunblock. Currently, SPF is the most standardized measure on the bottle. SPF stands for Sun Protection Factor and is an overall laboratory measure of the product effectiveness against UVB radiation only. It is an indication of the time a person can be exposed to sunlight before getting sunburned with a sunscreen applied relative to the time they can be exposed without sunscreen. For example, if someone who would burn after 20 minutes in the sun applied a sunscreen with SPF 15, it would take approximately 5 hours (300 minute) for them to burn. However, skin type, application, and activities all effect how long a sunscreen actually lasts. The main problem in this measurement system is that SPF gives no indication as to the amount of UVA protection. Even if a product has an SPF of 100 it may have absolutely no protective effect against UVA radiation. According to a 2003 study, sunscreens with an SPF of 30+ may actually have less protection against UVA. In the future you may see sunscreens in the US labeled with Persistent Pigment Darkening (PPD). This method is currently used in the EU for measuring UVA protection in a similar way that SPF measures UVB protection. Theoretically, a sunscreen with a PPD rating of 10 should allow you to endure 10 times as much UVA as you would without protection. The PPD should be at least 1/3 of the SPF to carry the UVA seal which will become more common in the US over the next couple of years.
Physical vs. Chemical Sunscreen
Physical sunscreens such as zinc oxide, titanium dioxide and iron oxide have a few distinct advantages over their chemical counterparts. First they work as soon as you put them on, they do not require the 30 minutes of absorption time necessary that chemical sunscreens need to work properly. Chemical sunscreens tend to release free radicals. When a chemical sunscreen receives UV energy it normally converts it into a chemical reaction sometimes leading to the formation of free radical. Although no data has conclusively linked chemical sunscreen with a specific type of cancer there is data that shows a higher melanoma rate in countries that use high amounts of chemical sunscreen1-2. Some chemical sunscreen ingredients (benzophenone-3, homosalate, 4-methyl-benzylidene camphor (4-MBC), octyl-methoxycinnamate and octyl-dimethyl-PABA) may act like an estrogen type of hormone after being absorbed, promoting endometriosis in women and decreased libido in men. There may also be a link between breast cancer and the increased use of chemical sunscreens3.
Full Spectrum
Now many products are labeled with the words, “Full Spectrum.” This means that the manufacturer claims the product will cover both UVA and UVB radiation. Although this gives a better indication about the coverage of the product there is no FDA standard as to what “Full Spectrum” means so virtually any manufacturer can put it on their bottle. In general it is better to look at the active ingredients and see Zinc Oxide or Titanium Dioxide, as both cover UVA and UVB.
Marketing Madness
The manufacturers of ingredients such as Mexoryl (Ecamsule), which is seen in products like Helioplex and Anthelios, have done a very good job of confusing the public. LaRoche and Neutrogena have both spent millions to convince the public and some doctors that this chemical sunscreen works better than the ones we have had around for 50 years. Mexoryl does cover a better range of UVA than do most chemical sunscreens and tends to stand up better to UVA over time than its predecessor avobenzone (Parsol 1789). However, products like Anthelios (which is actually a combination of Octocrylene, Mexoryl and Avobenzone) are still no more effective than the simple mixture of zinc oxide and titanium dioxide.
What to do?
Despite all the controversy most doctors would agree that sunscreen helps prevent photodamage and may help reduce the risk of certain types of skin cancer. Physical blocks are probably safer and more effective than chemical blocks. Use sunscreen over the face, neck and back of hands but do not be afraid to let the rest of your body get a little sun as it was designed to do. Use sunscreen on your face every day especially if you have Melasma (even on cloudy days 70% of UV light makes it to the ground). If you are doing outdoor activities apply about every 2-4 hours. If you are in the water, even with a water resistant sunscreen, reapply when you get out. In the end the most important ingredients in a sunscreen are Zinc Oxide and Titanium Dioxide. Titanium dioxide’s peak absorption is in the 290-340 range and Zinc’s peak absorption is in the 340-380 range. This combination is both safe for long term use and very effective in limiting solar skin damage from UVA and UVB. Brands like SkinCeuticals, which can be purchased in many doctor’s offices, use pure ingredients like micronized zinc which make them more cosmetically elegant, less likely to cause irritation and easy to use. Our favorite for adults, pregnant adults and kids alike is SkinCeuticals Physical Defense SPF 30, active ingredients: Zinc Oxide and Titanium Dioxide. by - David M. Verebelyi, MD
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