Sunscreen (also commonly known as sunblock, sun tan lotion, sun screen, sunburn cream or block out) 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 zinc oxide, or a combination of both).
- Organic particulates that mostly absorb light like organic chemical compounds, but contain multiple 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).
Medical organizations such as the  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 1946. 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. 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 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 sweat.
 Measurements of sunscreen protection
 Sun protection factor (SPF) and labeling requirements
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).
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. 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 highly 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 
Owing to consumer confusion over the real degree and duration of protection offered, labeling restrictions are in force in several countries. In the 
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).
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 
Mathematically, the SPF is calculated from measured data as
where is the solar irradiance spectrum, the erythemal action spectrum, and the monochromatic protection factor, all functions of the wavelength . 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.
 Measurements of UVA protection
 Persistent pigment darkening (PPD)
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.
 SPF equivalence
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,[
A set of final U.S. FDA rules effective from summer 2012 defines the phrase “broad spectrum” as having a UVA SPF at least as high as the UVB SPF.
 Star rating system
In the UK and Ireland, the 
 PA system
Asian brands, particularly Japanese ones, tend to use The Protection Grade of UVA (PA) system to measure the UVA protection a sunscreen provides.
The Protection Grade of UVA (PA) system is based on the PPD reaction and is now widely adopted on the labels of sunscreens. According to the Japan Cosmetic Industry Association PA+ corresponds to a UVA protection factor between two and four, PA++ between four and eight, and PA+++ more than eight.
 Sunblock is a type of sunscreen
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. 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.
 Potential health risks
||This article has been nominated to be checked for its neutrality. (January 2012)|
||This article needs attention from an expert in Medicine. (February 2012)|
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).
Some sunscreen lotions now include compounds such as Phlebodium aureum.
Some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells.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.
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. The authors emphasize that if enough sunscreen remains in the surface this effect would be eliminated, enhancing the message that sunscreen needs to be applied and reapplied sufficiently and correctly for it to work.
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.
Some epidemiological studies indicate an increased risk of 
Adverse health effects may be associated with some synthetic compounds in sunscreens.
Concerns have been raised regarding the use of nanoparticles in sunscreen. 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.” 
 Vitamin D
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).
This was leading to deficiency in Australia after a government campaign to increase sunscreen use.
 Active ingredients
The principal ingredients in sunscreens are usually  and various other photostabilisers.
 FDA allowable ingredients
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. 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|
|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-3,3-diphenyl acrylic acid, 2-ethylhexylester||10%||EC,USA, AUS, JP||Increases ROS|
|Octyl methoxycinnamate||Octinoxate, EMC, OMC, Ethylhexyl methoxycinnamate, 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|
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|
|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|
|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|
Other ingredients approved within the EU 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 ||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.
* Time and Extent Application (TEA), Proposed Rule on FDA approval expected 2009
||This section contains instructions, advice, or how-to content. (October 2009)|
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 that should block both UVA and UVB rays are called broad-spectrum sunscreens.
- 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.
- Sun rays are strongest between 10 am and 4 pm. 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.
The dose used in  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.
More recent research at the 
 Label regulations
Updated package labeling standards in the United States have been under development since 1978.
A set of final FDA rules effective from summer 2012 bans “waterproof” claims, instead requiring claims of 40 or 80 minutes “water-resistant” protection. It also requires a standardized “Drug Facts” label and requires specific FDA approval for “sunblock” and “instant protection” labels. Claims of protection over two hours are not allowed without specific approval.
However, the compliance dates for these new sunscreen labeling requirements, published in June 2011, have been delayed by 6 months. The new implementation date for products with annual sales less than US $25,000 is December 17, 2013 and that for all other products is December 17, 2012.
Due to requests by several trade associations and the personal care industry, the FDA ultimately decided to extend the implementation period for 6 months from the original compliance date. This decision allows manufacturers adequate time for thorough testing and the full implementation of the new labeling requirements which cover:
- Broad Spectrum designation
- Use claims
- “Waterproof,” “sweatproof” or “sunblock” claims
- Water resistance claims
- Drug facts
- Maximum SPF value on sunscreen labels to “50 +”
These changes shall enable consumers to identify and select suitable sunscreen products offering protection from sunburn, early skin aging and skin cancer.
 Hair care
Sunscreening agents are used in some hair care products such as shampoos, conditioners and styling agents to protect against protein degradation and color loss. Currently, Cinnamidopyltrimonium chloride and a few others are used to a much less degree. The common sunscreens used on skin are rarely used for hair products due to their texture and weight effects.
 See also
- “Preventing melanoma”. Cancer Research UK. http://www.cancerhelp.org.uk/help/default.asp?page=3007. Retrieved 2009-09-22.
- What You Need To Know About Skin Cancer
- Terence SC Poon, Ross StC Barnetson and Gary M Halliday (2003). “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”. J Invest Dermatol 121: 184-90.
- 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. . Retrieved 2009-09-25.
- MSNBC.com : Sunscreen — protection or ‘snake oil?'
- 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
- . Retrieved 2012-04-10.
- . 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
-  Questions and Answers on the 2007 Sunscreen Proposed Rule
- P. Schroeder, PhD and J. Krutmann, MD What is Needed for a Sunscreen to Provide Complete Protection
- 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.
- Vainio, H., Bianchini, F. (2000). “Cancer-preventive effects of sunscreens are uncertain”. Scandinavian Journal of Work Environment and Health 26: 529–31.
- Experts explore the safety of sunscreen | Straight.com
- CDC: Americans Carry Body Burden of Toxic Sunscreen Chemical | Environmental Working Group
- . 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.
- 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.
- . Retrieved 2009-09-25.
- Neutrogena | How Helioplex Works
- Banana Boat AvoTriplex
- DSM Nutritional Products North America – Cosmetics: Basis for Performance – Parsol 340 – Octocrylene
- 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
- Labeling and Effectiveness Testing; Sunscreen Drug Products for Over-the-Counter Human Use; Delay of Compliance Dates Retrieved 09/27/2012
- US FDA Delays Implementation Deadlines for Sunscreen Labeling Requirements SGS SafeGuard Bulletin, Retrieved 09/27/2012
- FDA rulemaking history for sunscreens
- FDA monograph on sunscreen
- FDA monograph on dosing, mechanism of action, and photodegradation of sunscreen (PDF file)
- Make sure your sunscreen has The Skin Cancer Foundation's Seal of Recommendation
- Environmental Working Group: July 2009 Sunscreen Safety Guide and Report
- Information on what sunscreens are and how they work from The Skin Cancer Foundation
- Sun Safety for Babies and Children University of Florida/IFAS Extension Department of Family, Youth and Community Sciences
- Article on UV absorbers not yet approved by the FDA
- Radiation protectants and their CAS registry number
- European Cosmetics ingredient database (CosIng)
- How does sunscreen work? Simple explanation from physics.org
This article uses material from the Wikipedia article Sunscreen, which is released under the Creative Commons Attribution-Share-Alike License 3.0.