Sunscreen (also commonly known as sunblock, sun tan lotion, sun screen, sun cream or block out)[1] is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's ultraviolet (UV) radiation on the skin exposed to sunlight and thus helps protect against sunburn. Skin-lightening products have sunscreen to protect lightened skin because light skin is more susceptible to sun damage than darker skin. A number of sunscreens have tanning powder to help the skin to darken or tan, however tanning powder does not provide protection from UV rays.
Sunscreens contain one or more of the following ingredients:
- Organic chemical compounds that absorb ultraviolet light.
- Inorganic particulates that reflect, scatter, and absorb UV light (such as titanium dioxide, zinc oxide, or a combination of both).
- Organic particulates that mostly absorb light like organic chemical compounds, but contain multiple chromophores, may reflect and scatter a fraction of light like inorganic particulates, and behave differently in formulations than organic chemical compounds. An example is Tinosorb M. Since the UV-attenuating efficacy depends strongly on particle size, the material is micronised to particle sizes below 200 nm. The mode of action of this photostable filter system is governed to about 90% by absorption and 10% by scattering of UV light.
Depending on the mode of action sunscreens can be classified into physical sunscreens (i.e., those that reflect the sunlight) or chemical sunscreens (i.e., those that absorb the UV light).[2]
Medical organizations such as the American Cancer Society recommend the use of sunscreen because it prevents the squamous cell carcinoma and the basal cell carcinoma.[3] However, the use of sunscreens is controversial for various reasons. Many sunscreens do not block UVA radiation, which does not cause sunburn but can increase the rate of melanoma, another kind of skin cancer, and photodermatitis, so people using sunscreens may be exposed to high UVA levels without realizing it. [4] The use of broad-spectrum (UVA/UVB) sunscreens can address this concern.
Although sunscreen is sometimes called "suntan lotion", the latter is different in that it is used to intensify UV rays whereas the former is used to block UV rays.
The first effective sunscreen may have been developed by chemist Franz Greiter in 1938. The product, called Gletscher Crème (Glacier Cream), subsequently became the basis for the company Piz Buin (named in honor of the place Greiter allegedly obtained the sunburn that inspired his concoction), which is still today a marketer of sunscreen products.[5] It has been estimated that Gletscher Crème had a sun protection factor of 2.
The first widely used sunscreen was produced by Benjamin Green, an airman and later a pharmacist, in 1944. The product, Red Vet Pet (for red veterinary petrolatum), had limited effectiveness, working as a physical blocker of ultraviolet radiation. It was a disagreeable red, sticky substance similar to petroleum jelly. This product was developed during the height of World War II, when it was likely that the hazards of sun overexposure were becoming apparent to soldiers in the Pacific and to their families at home. Sales of this product boomed when Coppertone acquired the patent and marketed the substance under the Coppertone girl and Bain de Soleil branding in the early 1950s.
Franz Greiter is credited with introducing the concept of sun protection factor (SPF) in 1962, which has become a worldwide standard for measuring the effectiveness of sunscreen when applied at an even rate of 2 milligrams per square centimeter (mg/cm2). Some controversy exists over the usefulness of SPF measurements, especially whether the 2 mg/cm2 application rate is an accurate reflection of people’s actual use.
Newer sunscreens have been developed with the ability to better withstand contact with water, heat and sweat.
Sunscreen helps prevent
sunburn, such as this, which has blistered
[edit] Sun protection factor (SPF) and labeling requirements
Two photographs showing the effect of applying sunscreen in visible light and in UVA. The photograph on the right was taken using
ultraviolet photography shortly after application of sunscreen to half of the face.
The sun protection factor of a sunscreen is 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).[2]
The SPF is the amount of UV radiation required to cause sunburn on skin with the sunscreen on, as a multiple of the amount required without the sunscreen.[6] There is a popular oversimplification of how SPF determines how long one can stay in the sun. For example, many users believe that, if they normally get sunburn in one hour, then an SPF 15 sunscreen allows them to stay in the sun fifteen hours (i.e. fifteen times longer) without getting sunburn. This would be true if the intensity of UV radiation were the same for the whole fifteen hours as in the one hour, but this is not normally the case. Intensity of solar radiation varies considerably with time of day. During early morning and late afternoon, the sun's radiation intensity is diminished since it must pass through more of the Earth's atmosphere while it is near the horizon.
In practice, the protection from a particular sunscreen depends, besides on SPF, 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, wavelength 320 to 400 nm), 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.[7][8][9] According to a 2004 study, UVA also causes DNA damage to cells deep within the skin, increasing the risk of malignant melanomas.[10] Even some products labeled "broad-spectrum UVA/UVB protection" do not provide good protection against UVA rays.[11] The best UVA protection is provided by products that contain zinc oxide, avobenzone, and ecamsule[citation needed]. Titanium dioxide probably gives good protection, but does not completely cover the entire UV-A spectrum, as recent research suggests that zinc oxide is superior to titanium dioxide at wavelengths between 340 and 380 nm.[12]
Owing to consumer confusion over the real degree and duration of protection offered, labeling restrictions are in force in several countries. In the EU sunscreen labels can only go up to SPF 50+ (actually indicating a SPF of 60 or higher)[13] while Australia's upper limit is 30+.[14] In the 2007 and 2011 draft rules, the Food and Drug Administration (FDA) proposed a maximum SPF label of 50, to limit unrealistic claims.[15][16]
Others have proposed restricting the active ingredients to an SPF of no more than 50, due to lack of evidence that higher dosages provide more meaningful protection (especially due to the logarithmic nature of the scale).[17]
File:Erythemal action spectrum.svg
UV-B sunlight spectrum (on a summer day in the Netherlands), along with the CIE Erythemal action spectrum. The effective spectrum is the product of the former two.
The SPF can be measured by applying sunscreen to the skin of a volunteer and measuring how long it takes before sunburn occurs when exposed to an artificial sunlight source. In the US, such an in vivo test is required by the FDA. It can also be measured in vitro with the help of a specially designed spectrometer. In this case, the actual transmittance of the sunscreen is measured, along with the degradation of the product due to being exposed to sunlight. In this case, the transmittance of the sunscreen must be measured over all wavelengths in the UV-B range (290–320 nm), along with a table of how effective various wavelengths are in causing sunburn (the erythemal action spectrum) and the actual intensity spectrum of sunlight (see the figure). Such in vitro measurements agree very well with in vivo measurements.[18] Numerous methods have been devised for evaluation of UVA and UVB protection. The most reliable spectrophotochemical methods eliminate the subjective nature of grading erythema.[19]
Mathematically, the SPF is calculated from measured data as
- Failed to parse (Missing texvc executable; please see math/README to configure.): \mathrm{SPF} = \frac{\int A(\lambda) E(\lambda)d\lambda}{\int A(\lambda) E(\lambda)/\mathrm{MPF}(\lambda) \, d\lambda},
where Failed to parse (Missing texvc executable; please see math/README to configure.): E(\lambda)
is the solar irradiance spectrum, Failed to parse (Missing texvc executable; please see math/README to configure.): A(\lambda)
the erythemal action spectrum, and Failed to parse (Missing texvc executable; please see math/README to configure.): \mathrm{MPF}(\lambda)
the monochromatic protection factor, all functions of the wavelength Failed to parse (Missing texvc executable; please see math/README to configure.): \lambda
. The MPF is roughly the inverse of the transmittance at a given wavelength.
The above means that the SPF is not simply the inverse of the transmittance in the UV-B region. If that were true, then applying two layers of SPF 5 sunscreen would be equivalent to SPF 25 (5 times 5). The actual combined SPF is always lower than the square of the single-layer SPF.
The persistent pigment darkening (PPD) method is a method of measuring UVA protection, similar to the SPF method of measuring UVB light protection. Originally developed in Japan, it is the preferred method used by manufacturers such as L'Oréal.
Instead of measuring erythema or reddening of the skin, the PPD method uses UVA radiation to cause a persistent darkening or tanning of the skin. Theoretically, a sunscreen with a PPD rating of 10 should allow a person 10 times as much UVA exposure as would be without protection. The PPD method is an in vivo test like SPF. In addition, Colipa has introduced a method that, it is claimed, can measure this in vitro and provide parity with the PPD method.[20]
The UVA seal used in the
EU
As part of revised guidelines for sunscreens in the EU, there is a requirement to provide the consumer with a minimum level of UVA protection in relation to the SPF. This should be a UVA PF of at least 1/3 of the SPF to carry the UVA seal. The implementation of this seal is in its phase-in period,[when?] so a sunscreen without it may already offer this protection.[21]
A set of final U.S. FDA rules going into effect for summer 2012 defines the phrase "broad spectrum" as having a UVA SPF at least as high as the UVB SPF.[16]
In the UK and Ireland, the Boots star rating system is a proprietary in vitro method used to describe the ratio of UVA to UVB protection offered by sunscreen creams and sprays. Based on original work by Prof. Brian Diffey at Newcastle University, the Boots Company in Nottingham, UK, developed a standard method that has been adopted by most companies marketing these products in the UK. The logo and methodology of the test are licenced for a token fee to any manufacturer or brand of sunscreens that are sold in the Boots retail chain, provided the products to which the logo is applied perform to the standard claimed. Own Label products exclusively sold in other retailers are now excluded from the terms of the licence. It should not be confused with SPF, which is measured with reference to burning and UVB. One-star products provide the least ratio of UVA protection; five-star products are best. The method has recently been revised in the light of the Colipa UVA PF test, and with the new EU recommendations regarding UVA PF. The method still uses a spectrophotometer to measure absorption of UVA vs UVB; the difference stems from a requirement to pre-irradiate samples (where this was not previously required) to give a better indication of UVA protection, and of photostability when the product is used. With the current methodology, the lowest rating is three stars, the highest being five stars. In August 2007, the FDA put out for consultation the proposal that a version of this protocol be used to inform users of American product of the protection that it gives against UVA,[22] but after concern this would be too confusing this was not adopted.[17]
Asian brands, particularly Japanese ones, tend to use the PA system to measure how light the cream is when you apply it to the skin. There are four levels: PA. PA+, PA++ and PA+++.
A tube of SPF 15 sun block lotion
Sunblock typically refers to opaque sunscreen that is effective at blocking both UVA and UVB rays and uses a heavy carrier oil to resist being washed off. Titanium dioxide and zinc oxide are two of the important ingredients in sunblock. Unlike the organic sun-blocking agents used in many sunscreens, these metal oxides do not degrade with exposure to sunlight.
The use of the word "sunblock" in the marketing of sunscreens is controversial. The FDA has considered banning such use because it can lead consumers to overestimate the effectiveness of products so labeled.[23]
For total protection against damage from the sun, the skin needs to be protected from UVA, UVB and IRA (infrared light). Roughly 35% of solar energy is IRA.[24]
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This article has been nominated to be checked for its neutrality. Discussion of this nomination can be found on the talk page. (January 2012) |
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As a defense against UV radiation, the amount of the brown pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, blocking the UV from damaging skin tissue. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. UVB on the other hand yields a tan that takes roughly two days to develop because it stimulates the body to produce more melanin. The photochemical properties of melanin make it an excellent photoprotectant.
Sunscreen chemicals, on the other hand, cannot dissipate the energy of the excited state as efficiently as melanin and therefore the penetration of sunscreen ingredients into the lower layers of the skin increases the amount of free radicals and reactive oxygen species (ROS).[25]
Some sunscreen lotions now include compounds such as titanium dioxide and zinc oxide, inert fillers which helps protect against UV rays via light scattering and physically blocking the light pathway into the dermal layers. Other UVA blocking compounds found in sunscreen include Avobenzone. There are also naturally occurring compounds found in rainforest plants that have been known to protect the skin from UV radiation damage, such as the fern Phlebodium aureum.
Some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells.[26][27][28] The amount of sunscreen that penetrates through the stratum corneum may be large enough to cause damage. In one study of sunscreens, the authors write:
The question whether UV filters acts on or in the skin has so far not been fully answered. Despite the fact that an answer would be a key to improve formulations of sun protection products, many publications carefully avoid addressing this question.[29]
In an experiment by Hanson et al. that was published in 2006, the amount of harmful reactive oxygen species was measured in untreated and in sunscreen-treated skin. In the first 20 minutes the film of sunscreen had a protective effect and the number of ROS species was smaller. After 60 minutes, however, the amount of absorbed sunscreen was so high that the amount of ROS was higher in the sunscreen-treated skin than in the untreated skin.[25]
George Zachariadis and E Sahanidou of the Laboratory of Analytical Chemistry, at Aristotle University, in Thessaloniki, Greece, have now carried out an ICP-AES analysis of several commercially available sunscreen creams and lotions. "The objective was the simultaneous determination of titanium and several minor, trace or toxic elements (aluminum, zinc, magnesium, iron, manganese, copper, chromium, lead, and bismuth) in the final products," the researchers say. They concluded that "Most of the commercial preparations that were studied showed generally good agreement to the ingredients listed on the product label." However, they also point out that the quantitative composition of the products tested cannot be assessed because the product labels usually do not provide a detailed break down of all ingredients and their concentrations. They also point out that, worryingly, their tests consistently revealed the presence of elements not cited in the product formulation, which emphasized the need for a standardized and official testing method for multi-element quality control of these products.[30]
Some epidemiological studies indicate an increased risk of malignant melanoma for the sunscreen user.[31][32][33][34][35][36][37][38] Despite these studies, no medical association has published recommendations to not use sunblock. Different meta-analysis publications have concluded that the evidence is not yet sufficient to claim a positive correlation between sunscreen use and malignant melanoma.[39][40]
Adverse health effects may be associated with some synthetic compounds in sunscreens.[41] In 2007 two studies by the CDC highlighted concerns about the sunscreen chemical oxybenzone (benzophenone-3). They first detected the chemicals in greater than 95% of 2000 Americans tested, while the second found that mothers with high levels of oxybenzone in their bodies were more likely to give birth to underweight baby girls.[42]
Concerns have been raised regarding the use of nanoparticles in sunscreen.[43] Theoretically, sunscreen nanoparticles could increase rates of certain cancers, or diseases similar to those caused by asbestos.[44] In 2006 the Therapeutic Goods Administration of Australia concluded a study and found:
"There is evidence from isolated cell experiments that zinc oxide and titanium dioxide can induce free radical formation in the presence of light and that this may damage these cells (photo-mutagenicity with zinc oxide). However, this would only be of concern in people using sunscreens if the zinc oxide and titanium dioxide penetrated into viable skin cells. The weight of current evidence is that they remain on the surface of the skin and in the outer dead layer (stratum corneum) of the skin." [43]
Artificial sunscreen absorbs ultraviolet light and prevents it from reaching the skin. It has been reported that sunscreen with a sun protection factor (SPF) of 8 based on the UVB spectrum can decrease vitamin D synthetic capacity by 95 percent, whereas sunscreen with an SPF of 15 can reduce synthetic capacity by 98 percent (Matsuoka et al., 1987).[45] Natural sunscreen has been proved to improve pigmentation from sun tanning.
This was leading to deficiency in Australia after a government campaign to increase sunscreen use.[46] Doctors recommend spending small amounts of time in the sun without sun protection to ensure adequate production of vitamin D.[47] When the UV index is greater than 3 (which occurs daily within the tropics and daily during the spring and summer seasons in temperate regions) adequate amounts of vitamin D3 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.[48]
The principal ingredients in sunscreens are usually aromatic molecules conjugated with carbonyl groups. This general structure allows the molecule to absorb high-energy ultraviolet rays and release the energy as lower-energy rays, thereby preventing the skin-damaging ultraviolet rays from reaching the skin. So, upon exposure to UV light, most of the ingredients (with the notable exception of avobenzone) do not undergo significant chemical change, allowing these ingredients to retain the UV-absorbing potency without significant photodegradation.[49] A chemical stabilizer is included in some sunscreens containing avobenzone to slow its breakdown - examples include formulations containing Helioplex[50] and AvoTriplex.[51] The stability of avobenzone can also be improved by bemotrizinol,[52] octocrylene[53] and various other photostabilisers.
The following are the FDA allowable active ingredients in sunscreens:
| UV-filter |
Other names |
Maximum concentration |
Permitted in these countries |
Results of safety testing |
| p-Aminobenzoic acid |
PABA |
15% (EC- banned from sale to consumers from 8 October 2009) |
USA, AUS |
Protects against skin tumors in mice.[54][55][56] Shown to increase DNA defects, however, and is now less commonly used. |
| Padimate O |
OD-PABA, octyldimethyl-PABA, σ-PABA |
8% (EC,USA,AUS) 10% (JP)
(Not currently supported in EU and may be delisted)
|
EC, USA, AUS, JP |
Not tested |
| Phenylbenzimidazole sulfonic acid |
Ensulizole, Eusolex 232, PBSA, Parsol HS |
4% (US,AUS) 8% (EC) 3% (JP) |
EC,USA, AUS, JP |
Genotoxic in bacteria[57] |
| Cinoxate |
2-Ethoxyethyl p-methoxycinnamate |
3% (US) 6% (AUS) |
USA, AUS |
Not tested |
| Dioxybenzone |
Benzophenone-8 |
3% |
USA, AUS |
Not tested |
| Oxybenzone |
Benzophenone-3, Eusolex 4360, Escalol 567 |
6% (US) 10% (AUS,EU) 5% (JP) |
EC, USA, AUS, JP |
Not tested |
| Homosalate |
Homomethyl salicylate, HMS |
10% (EC, JP) 15% (US,AUS) |
EC, USA, AUS, JP |
Not tested |
| Menthyl anthranilate |
Meradimate |
5% |
USA, AUS |
Not tested |
| Octocrylene |
Eusolex OCR, 2-cyano-3,3diphenyl acrylic acid, 2-ethylhexylester |
10% |
EC,USA, AUS, JP |
Increases ROS[25] |
| Octyl methoxycinnamate |
Octinoxate, EMC, OMC, Ethylmethoxycinnamate, Escalol 557, 2-ethylhexyl-paramethoxycinnamate, Parsol MCX |
7.5% (US) 10% (EC,AUS)20% (JP) |
EC,USA, AUS, JP |
|
| Octyl salicylate |
Octisalate, 2-Ethylhexyl salicylate, Escalol 587, |
5% (EC,USA,AUS) 10% (JP) |
EC,USA, AUS, JP |
Not tested |
| Sulisobenzone |
2-Hydroxy-4-Methoxybenzophenone-5-sulfonic acid,
3-benzoyl-4-hydroxy-6-methoxybenzenesulfonic acid, Benzophenone-4, Escalol 577
|
5% (EC) 10% (US, AUS, JP) |
EC,USA, AUS, JP |
|
| Trolamine salicylate |
Triethanolamine salicylate |
12% |
USA, AUS |
Not tested |
| Avobenzone |
1-(4-methoxyphenyl)-3-(4-tert-butyl
phenyl)propane-1,3-dione, Butyl methoxy dibenzoylmethane, BMDBM, Parsol 1789, Eusolex 9020 |
3% (US) 5% (EC,AUS)10% (JP) |
EC, USA, AUS, JP |
Not available[58] |
| Ecamsule |
Mexoryl SX, Terephthalylidene Dicamphor Sulfonic Acid |
10% |
EC,AUS (US:Approved in certain formulations up to 3% via New Drug Application (NDA) Route) |
Protects against skin tumors in mice[59][60][61] |
| Titanium dioxide |
CI77891 |
25% (No limit Japan) |
EC,USA, AUS, JP |
Not tested |
| Zinc oxide |
|
25% (US) 20% (AUS)
(EC-25% provided particle size >100 nm) (Japan, No Limit)
|
EC,USA, AUS, JP |
Protects against skin tumors in mice[59] |
Other ingredients approved within the EU[62] and other parts of the world,[63] that have not been included in the current FDA Monograph:
| UV-filter |
Other names |
Maximum concentration |
Permitted in |
| 4-Methylbenzylidene camphor |
Enzacamene, Parsol 5000, Eusolex 6300, MBC |
4%* |
EC, AUS |
| Tinosorb M |
Bisoctrizole, Methylene Bis-Benzotriazolyl Tetramethylbutylphenol, MBBT |
10%* |
EC, AUS, JP |
| Tinosorb S |
Bis-ethylhexyloxyphenol methoxyphenol triazine, Bemotrizinol, BEMT, anisotriazine |
10% (EC, AUS) 3% (JP)* |
EC, AUS, JP |
| Neo Heliopan AP |
Bisdisulizole Disodium, Disodium phenyl dibenzimidazole tetrasulfonate, bisimidazylate, DPDT |
10% |
EC, AUS |
| Mexoryl XL |
Drometrizole Trisiloxane |
15% |
EC, AUS |
| Benzophenone-9 |
Uvinul DS 49, CAS 3121-60-6, Sodium Dihydroxy Dimethoxy Disulfobenzophenone [64] |
10% |
JP |
| Uvinul T 150 |
Octyl triazone, ethylhexyl triazone, EHT |
5% (EC, AUS) 3% (JP)* |
EC, AUS |
| Uvinul A Plus |
Diethylamino Hydroxybenzoyl Hexyl Benzoate |
10% (EC,JP) |
EC, JP |
| Uvasorb HEB |
Iscotrizinol, Diethylhexyl butamido triazone, DBT |
10% (EC) 5% (JP) * |
EC, JP |
| Parsol SLX |
Dimethico-diethylbenzalmalonate, Polysilicone-15 |
10% |
EC, AUS, JP |
| Isopentenyl-4-methoxycinnamate |
Isoamyl p-Methoxycinnamate, IMC, Neo Heliopan E1000, Amiloxate |
10% * |
EC, AUS |
Many of the ingredients not approved by the FDA are relatively new and developed to absorb UVA.[65]
* Time and Extent Application (TEA), Proposed Rule on FDA approval expected 2009
Protection of the skin through use of a beach umbrella
Excessive exposure to direct sunlight is potentially harmful. Excessive exposure can result in sunburn if a person does not wear sun protective clothing or use suitable sunscreen. Products with a higher SPF (Sun Protection Factor) level provide greater protection against ultraviolet radiation. However, in 1998, the Annual Meeting of the American Association for the Advancement of Science reported that some sunscreens advertising UVA and UVB protection do not provide adequate safety from UVA radiation and could give sun tanners a false sense of protection. A sunscreen should also be hypoallergenic and noncomedogenic so it does not cause a rash or clog the pores, which can cause acne.
For those choosing to tan, some dermatologists recommend the following preventative measures:
- Sunscreens should block both UVA and UVB rays. These are called broad-spectrum sunscreens, which should also be hypoallergenic and noncomedogenic so they do not cause a rash or clog the pores, which can cause acne.
- Sunscreens need to be applied thickly enough to get the full SPF protection.
- Sunscreens should be applied 15 to 30 minutes before exposure, followed by one reapplication 15 to 30 minutes after the sun exposure begins. Further reapplication is necessary only after activities such as swimming, sweating, and rubbing.[66]
- Sun rays are strongest between 10 am and 4 pm.[67] Sun rays are stronger at higher elevations (mountains) and latitudes near the equator.
- Wearing a hat with a brim and anti-UV sunglasses can provide almost 100% protection against ultraviolet radiation's entering the eyes.
- Reflective surfaces like snow and water can greatly increase the amount of UV radiation to which the skin is exposed.
Recent evidence indicates that caffeine and caffeine sodium benzoate increase UVB-induced apoptosis both in topical and oral applications. In mice, UVB-induced hyperplasia was greatly reduced with administration of these substances. Although studies in humans remain untested, caffeine and caffeine sodium benzoate may be novel inhibitors of skin cancer.[68]
The dose used in FDA sunscreen testing is 2.2 mg/cm² of exposed skin.[49] Provided one assumes an "average" adult build of height 5 ft 4 in (163 cm) and weight 150 lb (68 kg) with a 32 in (82 cm) waist, that adult wearing a bathing suit covering the groin area should apply 29 g (approximately 1 oz) evenly to the uncovered body area. Considering only the face, this translates to about 1/4 to 1/3 of a teaspoon for the average adult face. Larger individuals should scale these quantities accordingly.
Contrary to the common advice that sunscreen should be reapplied every 2–3 hours, some research has shown that the best protection is achieved by application 15–30 minutes before exposure, followed by one reapplication 15–30 minutes after the sun exposure begins. Further reapplication is only necessary after activities such as swimming, sweating, or rubbing/wiping.[69]
More recent research at the University of California, Riverside, indicates that sunscreen must be reapplied within 2 hours in order to remain effective. Not reapplying could even cause more cell damage than not using sunscreen at all, due to the release of extra free radicals from those sunscreen chemicals that were absorbed into the skin.[25] Some studies have shown that people commonly apply only 1/2 to 1/4 of the amount recommended to achieve the rated sun protection factor (SPF), and in consequence the effective SPF should be downgraded to a square or 4th root of the advertised value.[70] A later study found a significant exponential relation between SPF and the amount of sunscreen applied and the results are closer to the linearity than expected by theory.[71]
Updated package labeling standards in the United States have been under development since 1978.
A set of final FDA rules going into effect for summer 2012 bans "waterproof" claims instead requiring claims of 40 or 80 minutes "water-resistant" protection. It also required a standardized "Drug Facts" label and requires specific FDA approval for "sunblock" and "instant protection" labels. Claims of protection over 2 hours are not allowed without specific approval.[16]
- ^ "Preventing melanoma". Cancer Research UK. http://www.cancerhelp.org.uk/help/default.asp?page=3007. Retrieved 2009-09-22.
- ^ a b Sunscreens | The Ageing Skin
- ^ What You Need To Know About Skin Cancer
- ^ {{cite journal | author=Terence SC Poon, Ross StC Barnetson and Gary M Halliday | title= Prevention of Immunosuppression by Sunscreens in Humans Is Unrelated to Protection from Erythema and Dependent on Protection from Ultraviolet A in the Face of Constant Ultraviolet B Protection | journal= J Invest Dermatol | volume=121 | pages=184-90 | year=2003 | (2003) 121, 184–190.
- ^ 70 years since the PIZ BUIN mountain inspired a man to invent the world's first sun protection cream
- ^ "Sunburn Protection Factor (SPF)". Food and Drug Administration (United States). 2009-04-30. http://www.fda.gov/AboutFDA/CentersOffices/CDER/ucm106351.htm. Retrieved 2009-09-25.
- ^ Stege, H.; Budde; Grether-Beck; Richard; Rougier; Ruzicka; Krutmann (2002). "Sunscreens with high SPF values are not equivalent in protection from UVA induced polymorphous light eruption". European journal of dermatology : EJD 12 (4): IV–VI. PMID 12118426. edit
- ^ Haywood, R.; Wardman, P.; Sanders, R.; Linge, C. (2003). "Sunscreens inadequately protect against ultraviolet-A-induced free radicals in skin: implications for skin aging and melanoma?". The Journal of investigative dermatology 121 (4): 862–868. DOI:10.1046/j.1523-1747.2003.12498.x. PMID 14632206. edit
- ^ Moyal, D.; Fourtanier, A. (2008). "Broad-spectrum sunscreens provide better protection from solar ultraviolet-simulated radiation and natural sunlight-induced immunosuppression in human beings". Journal of the American Academy of Dermatology 58 (5 Suppl 2): S149–S154. DOI:10.1016/j.jaad.2007.04.035. PMID 18410801. edit
- ^ Berneburg M, Plettenberg H, Medve-König K, Pfahlberg A, Gers-Barlag H, Gefeller O, Krutmann J (2004). "Induction of the photoaging-associated mitochondrial common deletion in vivo in normal human skin". J Invest Dermatol 122 (5): 1277–83. DOI:10.1111/j.0022-202X.2004.22502.x. PMID 15140232.
- ^ MSNBC.com : Sunscreen — protection or 'snake oil?'
- ^ Pinnell SR, Fairhurst D, Gillies R, Mitchnick MA, Kollias N (April 2000). "Microfine zinc oxide is a superior sunscreen ingredient to microfine titanium dioxide". Dermatol Surg 26 (4): 309–14. DOI:10.1046/j.1524-4725.2000.99237.x. PMID 10759815. http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=1076-0512&date=2000&volume=26&issue=4&spage=309.
- ^ Commission Recommendation of 22 September 2006 on the efficacy of sunscreen products and the claims made relating thereto. Official Journal of the European Union. 2006-09-22. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32006H0647:EN:NOT. Retrieved 2009-09-25.
- ^ "UV Resource Guide - Sunscreens". Arpansa. 2008-12-20. http://www.arpansa.gov.au/uvrg/rginfo_p13.cfm. Retrieved 2009-09-25.
- ^ Questions and Answers on the 2007 Sunscreen Proposed Rule
- ^ a b c "Questions and Answers: FDA announces new requirements for over-the-counter (OTC) sunscreen products marketed in the U.S.". 2011-06-23. http://www.fda.gov/Drugs/ResourcesForYou/Consumers/BuyingUsingMedicineSafely/UnderstandingOver-the-CounterMedicines/ucm258468.htm. Retrieved 2012-04-10.
- ^ a b "Sunscreen Takes Some Heat: New Dangers, New Rules". 2011-06-16. http://onpoint.wbur.org/2011/06/16/sunscreen. Retrieved 2012-04-10.
- ^ Optometrics products
- ^ Dominique Moyal "How to measure UVA protection afforded by suncreen products" www.medscape.com/viewarticle/576849
- ^ Colipa UVA method
- ^ www.colipa.com[dead link]
- ^ [1] Questions and Answers on the 2007 Sunscreen Proposed Rule
- ^ http://www.ewg.org/2010sunscreen/faqs-2010/#28
- ^ P. Schroeder, PhD and J. Krutmann, MD What is Needed for a Sunscreen to Provide Complete Protection
- ^ a b c d Hanson, KM; Gratton, E; Bardeen, CJ (2006). "Sunscreen enhancement of UV-induced reactive oxygen species in the skin". Free Radical Biology and Medicine 41 (8): 1205–12. DOI:10.1016/j.freeradbiomed.2006.06.011. PMID 17015167.
- ^ Xu, C; Green, Adele; Parisi, Alfio; Parsons, Peter G (2001). "Photosensitization of the Sunscreen Octyl p-Dimethylaminobenzoate b UVA in Human Melanocytes but not in Keratinocytes". Photochemistry and Photobiology 73 (6): 600–604. DOI:10.1562/0031-8655(2001)073<0600:POTSOP>2.0.CO;2. PMID 11421064.
- ^ Knowland, John; McKenzie, Edward A; McHugh, Peter J; Cridland, Nigel A (1993). "Sunlight-induced mutagenicity of a common sunscreen ingredient". FEBS Letters 324 (3): 309–313. DOI:10.1016/0014-5793(93)80141-G. PMID 8405372.
- ^ Damiani, E; Greci, L; Parsons, R; Knowland, (1999). "Nitroxide radicals protect DNA from damage when illuminated in vitro in the presence of dibenzoylmethane and a common sunscreen ingredient". Free Radic. Biol. Med. 26 (7–8): 809–816. DOI:10.1016/S0891-5849(98)00292-5. PMID 10232823.
- ^ Chatelaine, E.; Gabard, B.; Surber, C. (2003). "Skin penetration and sun protection factor of five UV filters: Effect of the vehicle". Skin Pharmacol. Appl. Skin Physiol 16 (1): 28–35. DOI:10.1159/000068291. PMID 12566826. http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ArtikelNr=68291&ProduktNr=224219&Ausgabe=228903&filename=68291.pdf.
- ^ David Bradley (August 15). "Toxic sunscreen testing". Http://www.spectroscopynow.com/coi/cda/detail.cda?id=22103&type=Feature&chId=1&page=1 year=2009.
- ^ Garland C, Garland F, Gorham E (04/01/1992). "Could sunscreens increase melanoma risk?". Am J Public Health 82 (4): 614–5. DOI:10.2105/AJPH.82.4.614. PMC 1694089. PMID 1546792. http://www.ajph.org/cgi/reprint/82/4/614.
- ^ Westerdahl, J.; Ingvar, C.; Masback, A.; Olsson, H. (2000). "Sunscreen use and malignant melanoma". International Journal of Cancer. Journal International Du Cancer 87 (1): 145–50. DOI:10.1002/1097-0215(20000701)87:1<145::AID-IJC22>3.0.CO;2-3. PMID 10861466.
- ^ Autier, P.; Dore, J. F.; Schifflers, E.; Al, et; Bollaerts, A; Koelmel, KF; Gefeller, O; Liabeuf, A et al. (1995). "Melanoma and use of sunscreens: An EORTC case control study in Germany, Belgium and France". Int. J. Cancer 61 (6): 749–755. DOI:10.1002/ijc.2910610602. PMID 7790106.
- ^ Weinstock, M. A. (1999). "Do sunscreens increase or decrease melanoma risk: An epidemiologic evaluation". Journal of Investigative Dermatology Symposium Proceedings 4 (1): 97–100. PMID 10537017.
- ^ Vainio, H., Bianchini, F. (2000). "Cancer-preventive effects of sunscreens are uncertain". Scandinavian Journal of Work Environment and Health 26: 529–31.
- ^ Wolf P, Quehenberger F, Müllegger R, Stranz B, Kerl H. (1998). "Phenotypic markers, sunlight-related factors and sunscreen use in patients with cutaneous melanoma: an Austrian case-control study". Melanoma Res. 8 (4): 370–378. DOI:10.1097/00008390-199808000-00012. PMID 9764814.
- ^ Graham S, Marshall J, Haughey B, Stoll H, Zielezny M, Brasure J, West D. (1985). "An inquiry into the epidemiology of melanoma". Am J Epidemiol. 122 (4): 606–619. PMID 4025303. http://www.ncbi.nlm.nih.gov.ezproxy.its.uu.se/sites/entrez.
- ^ Beitner H, Norell SE, Ringborg U, Wennersten G, Mattson B. (1990). "Malignant melanoma: aetiological importance of individual pigmentation and sun exposure". Br J Dermatol. 122 (1): 43–51. DOI:10.1111/j.1365-2133.1990.tb08238.x. PMID 2297503.
- ^ Huncharek M, Kupelnick B (July 2002). "Use of Topical Sunscreens and the Risk of Malignant Melanoma: A Meta-Analysis of 9067 Patients From 11 Case–Control Studies". Am J Public Health 92 (7): 1173–7. DOI:10.2105/AJPH.92.7.1173. PMC 1447210. PMID 12084704. http://www.ajph.org/cgi/pmidlookup?view=long&pmid=12084704.
- ^ Dennis LK, Beane Freeman LE, VanBeek MJ (December 2003). "Sunscreen use and the risk for melanoma: a quantitative review". Ann. Intern. Med. 139 (12): 966–78. PMID 14678916.
- ^ Experts explore the safety of sunscreen | Straight.com
- ^ CDC: Americans Carry Body Burden of Toxic Sunscreen Chemical | Environmental Working Group
- ^ a b "Safety of sunscreens containing nanoparticles of zinc oxide or titanium dioxide". February 2006. http://www.tga.gov.au/npmeds/sunscreen-zotd.htm. Retrieved 14 June 2009.
- ^ Arthur Martin (12 November 2008). "Revealed: The toxic nanoparticles with asbestos-like properties found in everyday goods". Daily Mail (London). http://www.dailymail.co.uk/news/article-1084931/Revealed-The-toxic-nanoparticles-asbestos-like-properties-everyday-goods.html. Retrieved 14 June 2009.
- ^ http://www.ncbi.nlm.nih.gov/books/NBK56078/
- ^ Sexton, Reid (2007-12-09). "Slip, slop, crack: the vitamin D crisis - National". Melbourne: theage.com.au. http://www.theage.com.au/articles/2007/12/08/1196813083745.html. Retrieved 2009-09-25.
- ^ Sexton, Reid; Hall, Louise (2007-12-09). "Be sun-smart, avoid bone D-generation risks - National". Melbourne: theage.com.au. http://www.theage.com.au/news/national/be-sunsmart-avoid-bone-dgeneration-risks/2007/12/08/1196813083751.html. Retrieved 2009-09-25.
- ^ "Dietary Supplement Fact Sheet: Vitamin D". National Institutes of Health. Archived from the original on 2007-09-10. http://www.webcitation.org/5Rl5u0LB5. Retrieved 2007-09-10.
- ^ a b "Re: Tentative Final Monograph for OTC Sunscreen". Food and Drug Administration (United States). 1998-09-11. http://www.fda.gov/ohrms/dockets/dailys/00/Sep00/090600/c000573_10_Attachment_F.pdf. Retrieved 2009-09-25.
- ^ Neutrogena | How Helioplex Works
- ^ Banana Boat AvoTriplex
- ^ Chatelain E, Gabard B. (September 2001). "Photostabilization of Butyl methoxydibenzoylmethane (Avobenzone) and Ethylhexyl methoxycinnamate by Bis-ethylhexyloxyphenol methoxyphenyl triazine (Tinosorb S), a new UV broadband filter". Photochem Photobiol 74 (3): 401–6. DOI:10.1562/0031-8655(2001)074<0401:POBMAA>2.0.CO;2. PMID 11594052.
- ^ DSM Nutritional Products North America - Cosmetics: Basis for Performance - Parsol 340 - Octocrylene
- ^ H Flindt-Hansen; P. Thune, T. Eeg-Larsen (1990). "The inhibiting effect of PABA on photocarcinogenesis". Archives of Dermatological Research 282 (1): 38–41. DOI:10.1007/BF00505643. PMID 2317082.
- ^ H Flindt-Hansen; P. Thune, T. Eeg-Larsen (1990). "The effect of short-term application of PABA on photocarcinogenesis". Acta Derm Venerol. 70 (1): 72–75. PMID 1967881.
- ^ P. J. Osgood; S. H. Moss, D. J. Davies (1982). "The sensitization of near-ultraviolet radiation killing of mammalian cells by the sunscreen agent para-aminobenzoic acid". Journal of Investigative Dermatology 79 (6): 354–357. DOI:10.1111/1523-1747.ep12529409. PMID 6982950.
- ^ Mosley, C N; Wang, L; Gilley, S; Wang, S; Yu, H (2007). "Light-Induced Cytotoxicity and Genotoxicity of a Sunscreen Agent, 2-Phenylbenzimidazol in Salmonella typhimurium TA 102 and HaCaT Keratinocytes". International Journal of Environmental Research and Public Health 4 (2): 126–131. DOI:10.3390/ijerph2007040006. PMID 17617675.
- ^ Nash, JF (2006). "Human Safety and Efficacy of Ultraviolet Filters and Sunscreen Products". Dermatologic Clinics 24 (1): 35–51. DOI:10.1016/j.det.2005.09.006. PMID 16311166.
- ^ a b Lautenschlager, Stephan; Wulf, Hans Christian; Pittelkow, Mark R (2007). "photoprotection". Lancet 370 (9586): 528–37. DOI:10.1016/S0140-6736(07)60638-2. PMID 17693182.
- ^ Benech-Kieffer F, Meuling WJ, Leclerc C, Roza L, Leclaire J, Nohynek G (Nov-Dec 2003). "Percutaneous absorption of Mexoryl SX in human volunteers: comparison with in vitro data". Skin Pharmacol Appl Skin Physiol 16 (6): 343–55. DOI:10.1159/000072929. PMID 14528058.
- ^ Fourtanier A (October 1996). "Mexoryl SX protects against solar-simulated UVR-induced photocarcinogenesis in mice". Photochem Photobiol 64 (4): 688–93. DOI:10.1111/j.1751-1097.1996.tb03125.x. PMID 8863475.
- ^ CL1976L0768EN0150010.0001 1..107
- ^ Australian Regulatory Guidelines for OTC Medicines - Chapter 10
- ^ "Uvinul Grades" (PDF). http://www.basf-korea.co.kr/02_products/04_finechemicals/document/cosmetic/tech/uvabsorber/down.asp?file=uvinulgrades.pdf. Retrieved 2009-09-25.
- ^ Manage Account - Modern Medicine
- ^ Diffey, B.L. (2001). "When should sunscreen be reapplied?". J Am Acad Dermatol. 45 (6): 882–5. DOI:10.1067/mjd.2001.117385. PMID 11712033.
- ^ http://www.epa.gov/sunwise/actionsteps.htm[dead link]
- ^ Conney, Allan H; Kramata, P; Lou, YR; Lu, YP (2008). "Effect of Caffeine on UVB-induced Carcinogenesis, Apoptosis, and the Elimination of UVB-induced Patches of p53 Mutant Epidermal Cells in SKH-1 Mice". Photochemistry and Photobiology 84 (2): 330–338. DOI:10.1111/j.1751-1097.2007.00263.x. PMID 18179623. http://www.ingentaconnect.com/content/bpl/php/2008/00000084/00000002/art00010.
- ^ Diffey B (2001). "When should sunscreen be reapplied?". J Am Acad Dermatol 45 (6): 882–5. DOI:10.1067/mjd.2001.117385. PMID 11712033.
- ^ Faurschou A, Wulf HC (April 2007). "The relation between sun protection factor and amount of sunscreen applied in vivo". Br. J. Dermatol. 156 (4): 716–9. DOI:10.1111/j.1365-2133.2006.07684.x. PMID 17493070.
- ^ Schalka S, dos Reis VM, Cucé LC (August 2009). "The influence of the amount of sunscreen applied and its sun protection factor (SPF): evaluation of two sunscreens including the same ingredients at different concentrations". Photodermatol Photoimmunol Photomed 25 (4): 175–80. DOI:10.1111/j.1600-0781.2009.00408.x. PMID 19614894.
Sunscreening agents approved by the US FDA or other agencies
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UVA: 400–315 nm • UVB: 315–290 nm • chemical agents unless otherwise noted
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