ULTRAVIOLET LIGHT
Ultraviolet (UV) light, also known as ultraviolet radiation, is produced by the sun and is invisible to the human eye. Compared to visible light, UV light has a shorter wavelength, which equates to higher frequency and higher energy. It is named "ultraviolet" because it is just beyond violet light on the electromagnetic spectrum.
Due to its high energy, UV light damages the skin. Excessive exposure to UV light causes, among other forms of damage, DNA mutations to skin cells which lead to skin cancer.
If we could see UV light, we would no doubt subcategorize it by its "colors". As it is invisible, however, we subcategorize it into three basic groups: A, B, and C.
UVA and UVB cause skin damage. Of the two, UVB has higher energy. UVB is the cause of sunburn, while UVA damages the skin without any detectable sunburn.
UVC doesn't reach the Earth's surface: it is blocked out by the Earth's atmosphere. As such, it doesn't reach the skin to cause problems.
MELANIN PIGMENT
One of the ways human skin protects itself from UV light is by
producing melanin pigment. Melanin is a chemical that absorbs UV
light. Melanin is stored in the outer layers of skin, decreasing
UV penetration into the skin. Melanin also absorbs and reflects
visible light, giving the skin its color. Genetics determines the
amount of melanin the skin produces. Individuals whose ancestors
come from sunny environments tend to produce the most melanin pigment,
which is manifested by dark skin color.
Light-colored skin produces little melanin pigment. As such, people with light skin are at higher risk for skin cancer.
Pigment production can also be induced by UV damage. This is known as tanning and freckling. The damage required to produce tanning and freckling increases the risk of skin cancer.
Light-colored skin produces little melanin pigment. As such, people with light skin are at higher risk for skin cancer.
Pigment production can also be induced by UV damage. This is known as tanning and freckling. The damage required to produce tanning and freckling increases the risk of skin cancer.
SUN-PROTECTIVE BEHAVIOR
Sun-protective behavior is especially important for individuals at high risk for skin cancer. Sun-protective behavior employs shade, hats, clothing, sunglasses, and sunscreen.
Shade prevents direct sunlight from striking the skin. Some shade materials are impermeable to UV light, while others are semi-permeable. Shaded skin is still susceptible to reflected UV light. An example of this is an umbrella at the beach: the shaded area under the umbrella is still exposed to sunlight reflected off nearby sand.
Hats are shade structures fitted for the human head. In addition to protecting the scalp, a wide-brimmed hat shades the face, ears, and neck: the areas that produce the most skin cancer. Baseball caps are a poor substitute for a brimmed hat, but they're better than no hat.
Clothing is a shade structure fitted for the body.
Sunglasses help screen out UV light from damaging the eyes and eyelids.
Sunscreen, available in lotion and in other vehicles applied to the skin, helps decrease UV light penetration. Sunscreens contain ingredients that absorb and/or reflect ultraviolet light.
Sun-protective behavior is especially important for individuals at high risk for skin cancer. Sun-protective behavior employs shade, hats, clothing, sunglasses, and sunscreen.
Shade prevents direct sunlight from striking the skin. Some shade materials are impermeable to UV light, while others are semi-permeable. Shaded skin is still susceptible to reflected UV light. An example of this is an umbrella at the beach: the shaded area under the umbrella is still exposed to sunlight reflected off nearby sand.
Hats are shade structures fitted for the human head. In addition to protecting the scalp, a wide-brimmed hat shades the face, ears, and neck: the areas that produce the most skin cancer. Baseball caps are a poor substitute for a brimmed hat, but they're better than no hat.
Clothing is a shade structure fitted for the body.
Sunglasses help screen out UV light from damaging the eyes and eyelids.
Sunscreen, available in lotion and in other vehicles applied to the skin, helps decrease UV light penetration. Sunscreens contain ingredients that absorb and/or reflect ultraviolet light.
MAKING SENSE OF SUNSCREEN
Shade, hats, clothing, and sunglasses are easily understood as sun protection modalities because they screen out visible light in addition to UV light. The screening of visible light allows us to see the pattern of shade produced. Sunscreen, on the other hand, screens out only UV light, which is invisible. As such, the sunscreen process cannot be seen by the human eye.
The great challenge to the skincare industry is to design a product that screens out all UV light without reflecting any visible light. After all, visible light is visible. A thick application of white zinc oxide paste on the nose of a lifeguard effectively screens out UV light, but it also reflects visible light, giving a look that has limited appeal to the public for daily use. As such, with the limitation of requiring a product to "disappear" when rubbed into the skin, the skincare industry has not yet been able to invent a sunscreen that blocks out all UV light; even the best sunscreens only screen out a portion of UV light.
As it is farther away from visible light on the electromagnetic spectrum, UVB is relatively easy to screen out with a "disappearing" product. As such, most sunscreens are reasonably effective at screening out UVB light. As UVB exposure is the cause of sunburn, most sunscreens are fairly successful at diminishing sunburn.
Screening out UVA light with a "disappearing" product is a more difficult task, because UVA is adjacent to visible light on the electromagnetic spectrum. Thus, many sunscreens screen out minimal UVA light.
"Broad-spectrum" is a phrase manufacturers use to promote sunscreens with what they deem acceptable UVA coverage. "Blocks UVA and UVB" is another phrase commonly seen on sunscreen labels. Neither phrase informs the consumer of the amount of UVA coverage offered.
Sun Protection Factor (SPF) is a sunscreen rating system based on the length of time an applied sunscreen has been proven to protect the skin from sunburn. This system was designed at a time when sunburn was believed to be an accurate indicator of overall sun damage. Subsequent research shows, however, that most sun damage occurs without a burn. The SPF system, therefore, is unable to accurately rate the effectiveness of a sunscreen.
Dermatologists currently recommend that consumers select sunscreens based on their ingredients. Of the active ingredients found in today's sunscreens, those that best screen out UVA are:
Shade, hats, clothing, and sunglasses are easily understood as sun protection modalities because they screen out visible light in addition to UV light. The screening of visible light allows us to see the pattern of shade produced. Sunscreen, on the other hand, screens out only UV light, which is invisible. As such, the sunscreen process cannot be seen by the human eye.
The great challenge to the skincare industry is to design a product that screens out all UV light without reflecting any visible light. After all, visible light is visible. A thick application of white zinc oxide paste on the nose of a lifeguard effectively screens out UV light, but it also reflects visible light, giving a look that has limited appeal to the public for daily use. As such, with the limitation of requiring a product to "disappear" when rubbed into the skin, the skincare industry has not yet been able to invent a sunscreen that blocks out all UV light; even the best sunscreens only screen out a portion of UV light.
As it is farther away from visible light on the electromagnetic spectrum, UVB is relatively easy to screen out with a "disappearing" product. As such, most sunscreens are reasonably effective at screening out UVB light. As UVB exposure is the cause of sunburn, most sunscreens are fairly successful at diminishing sunburn.
Screening out UVA light with a "disappearing" product is a more difficult task, because UVA is adjacent to visible light on the electromagnetic spectrum. Thus, many sunscreens screen out minimal UVA light.
"Broad-spectrum" is a phrase manufacturers use to promote sunscreens with what they deem acceptable UVA coverage. "Blocks UVA and UVB" is another phrase commonly seen on sunscreen labels. Neither phrase informs the consumer of the amount of UVA coverage offered.
Sun Protection Factor (SPF) is a sunscreen rating system based on the length of time an applied sunscreen has been proven to protect the skin from sunburn. This system was designed at a time when sunburn was believed to be an accurate indicator of overall sun damage. Subsequent research shows, however, that most sun damage occurs without a burn. The SPF system, therefore, is unable to accurately rate the effectiveness of a sunscreen.
Dermatologists currently recommend that consumers select sunscreens based on their ingredients. Of the active ingredients found in today's sunscreens, those that best screen out UVA are:
- titanium dioxide
- zinc oxide
- avobenzone
- ecamsule
It is recommended that sunscreens contain one or more of these
ingredients. Of interest, titanium dioxide and zinc oxide are referred
to as physical sunscreens, meaning they reflect UV light.
Avobenzone, (marketed as Parsol 1789) and ecamsule (marketed as
mexoryl) are chemical sunscreens, meaning they absorb UV light.
There is little data available in regard to the stability of sunscreen ingredients over time and with exposure to heat, sunlight, water, and skin surface chemistry. Reapplication of sunscreen during prolonged periods of sun and water exposure is recommended by product manufacturers.
"Sunblock" is an outdated term. "Sunscreen," suggesting permeability, is the currently-preferred term. Likewise, the term "waterproof" has been, for the most part, replaced with the less-grandiose term "water-resistant."
"PABA-free" indicates that a product doesn't contain para-aminobenzoic acid, a sunscreen ingredient with a propensity for causing skin allergy.
Any topically-applied product, sunscreens included, can promote acne on acne-prone skin surfaces. In order to reduce acne problems, sunscreens designed for the face tend to be less oily, less water-resistant, and less UV-protective than sunscreens designed for general use.
Sunscreen is an important part of a thorough skin-protection regimen that includes shade, hats, clothing, and sunglasses. Sunscreen alone, however, due to its above-mentioned limitations, is only mildly effective at preventing sun damage.
There is little data available in regard to the stability of sunscreen ingredients over time and with exposure to heat, sunlight, water, and skin surface chemistry. Reapplication of sunscreen during prolonged periods of sun and water exposure is recommended by product manufacturers.
"Sunblock" is an outdated term. "Sunscreen," suggesting permeability, is the currently-preferred term. Likewise, the term "waterproof" has been, for the most part, replaced with the less-grandiose term "water-resistant."
"PABA-free" indicates that a product doesn't contain para-aminobenzoic acid, a sunscreen ingredient with a propensity for causing skin allergy.
Any topically-applied product, sunscreens included, can promote acne on acne-prone skin surfaces. In order to reduce acne problems, sunscreens designed for the face tend to be less oily, less water-resistant, and less UV-protective than sunscreens designed for general use.
Sunscreen is an important part of a thorough skin-protection regimen that includes shade, hats, clothing, and sunglasses. Sunscreen alone, however, due to its above-mentioned limitations, is only mildly effective at preventing sun damage.