Sunscreen, also known as sunblock, sun lotion or sun cream, is a photoprotection topical product for the Human skin that helps protect against sunburn and prevent skin cancer. Sunscreens come as , sprays, gels, foams (such as an expanded foam lotion or whipped lotion), sticks, powders and other topical products. Sunscreens are common supplements to clothing, particularly sunglasses, and special sun protective clothing, and other forms of photoprotection (such as ).
Sunscreens may be classified according to the type of active ingredient(s) present in the formulation (inorganic compounds or organic compound) as:
Medical organizations such as the American Cancer Society recommend the use of sunscreen because it aids in the prevention of squamous cell carcinomas. The routine use of sunscreens may also reduce the risk of melanoma. To effectively protect against all the potential damages of UV light, the use of broad-spectrum sunscreens (covering both UVA and UVB radiation) has been recommended.
In 1820, Sir Everard Home, an English physician, conducted observational experiences that suggested there is something other than heat from the sun that causes sunburns. He also documented the protective effect of having dark skin on sun burns.Home, E. (1821). On the Black Rete Mucosum of the Negro, Being a Defense against the Scorching Effect of the Sun’s Rays. Philosophical transactions of the Royal, 111(1), 1–6.
The US military was an early adopter of sunscreen. In 1944, as the hazards of sun overexposure became apparent to soldiers stationed in the Pacific tropics at the height of World War II, Benjamin Green, an airman and later a pharmacist produced Red Vet Pet (for red veterinary petrolatum) for the US military. Sales boomed when Coppertone improved and commercialized the substance under the Coppertone girl and Bain de Soleil branding in the early 1950s. In 1946, chemist Franz Greiter introduced a product, called Gletscher Crème (Glacier Cream), subsequently became the basis for the company Piz Buin, named in honor of Piz Buin where Greiter allegedly received the sunburn.
In 1974, Greiter adapted earlier calculations from Friedrich Ellinger and Rudolf Schulze and introduced the "sun protection factor" (SPF), which has become the global standard for measuring UVB protection. It has been estimated that Gletscher Crème had an SPF of 2.
Water-resistant sunscreens were introduced in 1977, and recent development efforts have focused on overcoming later concerns by making sunscreen protection both longer-lasting and broader-spectrum (protection from both UVA & UVB rays), more environmentally friendly, more appealing to use and addressing the safety concerns of petrochemical sunscreens, i.e. FDA studies showing their systematic absorption into the bloodstream.
A 2013 study concluded that the diligent, everyday application of sunscreen could slow or temporarily prevent the development of wrinkles and sagging skin. The study involved 900 light skin people in Australia and required some of them to apply a broad-spectrum sunscreen every day for four and a half years. It found that people who did so had noticeably more resilient and smoother skin than those assigned to continue their usual practices. A study on 32 subjects showed that daily use of sunscreen (SPF 30) reversed photoaging of the skin within 12 weeks and the amelioration continued until the end of the investigation period of one year. Sunscreen is inherently anti-aging as the sun is the number-one cause of premature aging; it therefore may slow or temporarily prevent the development of wrinkles, dark spots and sagging skin.
Minimizing UV damage is especially important for children and light-skinned individuals and those who have sun sensitivity for medical reasons, including medical use of retinoids.
Regulators can investigate and ban UV filters over safety concerns (such as PABA), which can result in withdrawal of products from the consumer market. Regulators such as the TGA and the FDA have also been concerned with recent reports of contamination in sunscreen products with known possible human carcinogens such as benzene and benzophenone. Independent laboratory testing carried out by Valisure found benzene contamination in 27% of the sunscreens they tested, with some batches having up to triple the FDA's conditionally restricted limit of 2 parts per million (ppm). This resulted in a voluntary recall by some major sunscreen brands that were implicated in the testing, as such, regulators also help publicise and coordinate these voluntary recalls. V.O.C.s (Volatile Organic Compounds) such as benzene, are particularly harmful in sunscreen formulations as many active and inactive ingredients can increase permeation across the skin. Butane, which is used as a propellant in spray sunscreens, has been found to have benzene impurities from the refinement process.
There is a risk of an allergic reaction to sunscreen for some individuals, as "Typical allergic contact dermatitis may occur in individuals allergic to any of the ingredients that are found in sunscreen products or cosmetic preparations that have a sunscreen component. The rash can occur anywhere on the body where the substance has been applied and sometimes may spread to unexpected sites."
High-SPF sunscreens filter out most UVB radiation, which triggers vitamin D production in the skin. However, clinical studies show that regular sunscreen use does not lead to vitamin D deficiency. Even high-SPF sunscreens allow a small amount of UVB to reach the skin, sufficient for vitamin D synthesis. Additionally, brief, unprotected sun exposure can produce ample vitamin D, but this exposure also risks significant DNA damage and skin cancer. To avoid these risks, vitamin D can be obtained safely through diet and supplements. Foods like Oily fish, fortified milk, and orange juice, along with supplements, provide necessary vitamin D without harmful sun exposure.
Studies have shown that sunscreen with a high UVA protection factor enabled significantly higher vitamin D synthesis than a low UVA protection factor sunscreen, likely because it allows more UVB transmission.
The SPF is an imperfect measure of skin damage because invisible damage and skin malignant melanomas are also caused by ultraviolet A (UVA, wavelengths 315–400 or 320–400 nanometre), which does not primarily 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. According to a 2004 study, UVA also causes DNA damage to cells deep within the skin, increasing the risk of malignant melanomas. Even some products labeled "broad-spectrum UVA/UVB protection" have not always provided good protection against UVA rays. Titanium dioxide probably gives good protection but does not completely cover the UVA spectrum, with early 2000s research suggesting that zinc oxide is superior to titanium dioxide at wavelengths 340–380 nm.
Owing to consumer confusion over the real degree and duration of protection offered, labelling restrictions are enforced in several countries. In the European Union, sunscreen labels can only go up to SPF 50+ (initially listed as 30 but soon revised to 50). Australia's Therapeutic Goods Administration increased the upper limit to 50+ in 2012. In its 2007 and 2011 draft rules, the US Food and Drug Administration (FDA) proposed a maximum SPF label of 50, to limit unrealistic claims. (As of August 2019, the FDA has not adopted the SPF 50 limit.) 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. Different sunscreen ingredients have different effectiveness against UVA and UVB.
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 sunlight's UVB–UVA range (290–400 nm), along with a table of how effective various wavelengths are in causing sunburn (the erythemal action spectrum) and the standard intensity spectrum of sunlight (see the figure). Such in vitro measurements agree very well with in vivo measurements.
Numerous methods have been devised for evaluation of UVA and UVB protection. The most-reliable spectrophotochemical methods eliminate the subjective nature of grading erythema.
The ultraviolet protection factor (UPF) is a similar scale developed for rating fabrics for sun protective clothing. According to recent testing by Consumer Reports, UPF ~30+ is typical for protective fabrics, while UPF ~20 is typical for standard summer fabrics.
Mathematically, the SPF (or the UPF) 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 combined SPF of two layers of sunscreen may be lower than the square of the single-layer SPF.
Instead of measuring erythema, 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, the European Cosmetic and Perfumery Association ( Colipa) has introduced a method that, it is claimed, can measure this in vitro and provide parity with the PPD method.
A set of final US FDA rules effective from summer 2012 defines the phrase "broad spectrum" as providing UVA protection proportional to the UVB protection, using a standardized testing method.
One-star products provide the lowest ratio of UVA protection, five-star products the highest. The method was revised in light of the Colipa UVA PF test and the revised EU recommendations regarding UVA PF. The method still uses a spectrophotometer to measure absorption of UVA versus 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 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; but this was not adopted, for fear it would be too confusing.
The organic compounds used as UV filter are often aromaticity 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. A chemical stabilizer is included in some sunscreens containing avobenzone to slow its breakdown. The stability of avobenzone can also be improved by bemotrizinol, octocrylene and various other photostabilisers. Most organic compounds in sunscreens slowly degrade and become less effective over the course of several years even if stored properly, resulting in the shelf life calculated for the product.
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, benzophenone-4 and ethylhexyl methoxycinnamate are the two sunscreens most commonly used in hair products. The common sunscreens used on skin are rarely used for hair products due to their texture and weight effects.
UV filters need usually to be approved by local agencies (such as the FDA in the United States) to be used in sunscreen formulations. As of 2023, 29 compounds are approved in the European Union and 17 in the USA. No new UV filters have been approved by the FDA for use in cosmetics since 1999.
The following are the FDA allowable active ingredients in sunscreens:
Other ingredients approved within the EU and other parts of the world, that have not been included in the current FDA Monograph:
* Time and Extent Application (TEA), Proposed Rule on FDA approval originally expected 2009, now expected 2015.
Many of the ingredients awaiting approval by the FDA are relatively new, and developed to absorb UVA. The 2014 Sunscreen Innovation Act was passed to accelerate the FDA approval process.
When combined with UV filters, added can work synergistically to affect the overall SPF value positively. Furthermore, adding antioxidants to sunscreen can amplify its ability to reduce markers of extrinsic photoaging, grant better protection from Liver spot, mitigate skin lipid peroxidation, improve the photostability of the active ingredients, neutralize reactive oxygen species formed by irradiated photocatalysts (e.g., uncoated TiO₂) and aid in DNA repair post-UVB damage, thus enhancing the efficiency and safety of sunscreens. Compared with sunscreen alone, it has been shown that the addition of antioxidants has the potential to suppress ROS formation by an additional 1.7-fold for SPF 4 sunscreens and 2.4-fold for SPF 15-to-SPF 50 sunscreens, but the efficacy depends on how well the sunscreen in question has been formulated. Sometimes are also incorporated into commercially available sunscreens in addition to antioxidants since they also aid in protecting the skin from the detrimental effects of UVR. Examples include the osmolyte taurine, which has demonstrated the ability to protects against UVB-radiation induced immunosuppression and the osmolyte ectoine, which aids in counteracting cellular accelerated aging & UVA-radiation induced premature photoaging.
Other inactive ingredients can also assist in photostabilizing unstable UV filters. have demonstrated the ability to reduce photodecomposition, protect antioxidants and limit skin penetration past the Stratum corneum, allowing them to longer maintain the protection factor of sunscreens with UV filters that are highly unstable and/or easily permeate to the lower layers of the skin. Similarly, film-forming polymers like polyester-8 and polycryleneS1 have the ability to protect the efficacy of older petrochemical UV filters by preventing them from destabilizing due to extended light exposure. These kinds of ingredients also increase the water resistance of sunscreen formulations.
In the 2010s and 2020s, there has been increasing interest in sunscreens that protect the wearer from the sun's high-energy visible light and infrared as well as ultraviolet light. This is due to newer research revealing blue & violet visible light and certain wavelengths of infrared light (e.g., NIR, IR-A) work synergistically with UV light in contributing to oxidative stress, free radical generation, dermal cellular damage, suppressed skin healing, decreased immunity, erythema, inflammation, dryness, and several aesthetic concerns, such as: wrinkle formation, loss of skin elasticity and dyspigmentation. Increasingly, a number of commercial sunscreens are being produced that have manufacturer claims regarding skin protection from blue light, infrared light and even air pollution. However, as of 2021 there are no regulatory guidelines or mandatory testing protocols that govern these claims. Historically, the American FDA has only recognized protection from sunburn (via UVB protection) and protection from skin cancer (via SPF 15+ with some UVA protection) as drug/medicinal sunscreen claims, so they do not have regulatory authority over sunscreen claims regarding protecting the skin from damage from these other environmental stressors. Since sunscreen claims not related to protection from ultraviolet light are treated as cosmeceutical claims rather than drug/medicinal claims, the innovative technologies and additive ingredients used to allegedly reduce the damage from these other environmental stressors may vary widely from brand to brand.
Some studies show that mineral sunscreens primarily made with substantially large particles (i.e., neither nano nor micronized) may help protect from visible and infrared light to some degree, but these sunscreens are often unacceptable to consumers due to leaving an obligatory opaque white cast on the skin. Further research has shown that sunscreens with added Iron oxide and/or pigmentary titanium dioxide can provide the wearer with a substantial amount of HEVL protection. Cosmetic chemists have found that other cosmetic-grade pigments can be functional filler ingredients. Mica was discovered to have significant synergistic effects with UVR filters when formulated in sunscreens, in that it can notably increase the formula's ability to protect the wearer from HEVL.
There is a growing amount of research demonstrating that adding various vitamer antioxidants (eg; retinol, Gamma-Tocopherol, tocopheryl acetate, Vitamin C, ascorbyl tetraisopalmitate, ascorbyl palmitate, sodium ascorbyl phosphate, ubiquinone) and/or a mixture of certain botanical antioxidants (eg; epigallocatechin-3-gallate, Beta-Carotene, vitis vinifera, Silybum marianum, spirulina extract, Chamomile and possibly others) to sunscreens efficaciously aids in reducing damage from the free radicals produced by exposure to solar ultraviolet radiation, visible light, near infrared radiation and infrared-a radiation. Since sunscreen's active ingredients work preventatively by creating a shielding film on the skin that absorbs, scatters, and reflects light before it can reach the skin, UV filters have been deemed an ideal “first line of defense” against sun damage when exposure can't be avoided. Antioxidants have been deemed a good “second line of defense” since they work responsively by decreasing the overall burden of free radicals that do reach the skin. The degree of the free radical protection from the entire solar spectral range that a sunscreen can offer has been termed the "radical protection factor" (RPF) by some researchers.
The dose used in FDA sunscreen testing is 2 mg/cm2 of exposed skin. If one assumes an "average" adult build of height 5 ft 4 in (163 cm) and weight 150 lb (68 kg) with a 32-inch (82-cm) waist, that adult wearing a bathing suit covering the groin area should apply approximately 30 g (or 30 ml, approximately 1 oz) evenly to the uncovered body area. This can be more easily thought of as a "golf ball" size amount of product per body, or at least six teaspoonfuls. Larger or smaller individuals should scale these quantities accordingly. Considering only the face, this translates to about 1/4 to 1/3 of a teaspoon for the average adult face.
Some studies have shown that people commonly apply only 1/4 to 1/2 of the amount recommended for achieving the rated sun protection factor (SPF), and in consequence the effective SPF should be downgraded to a 4th root or a square root of the advertised value, respectively. A later study found a significant exponential relation between SPF and the amount of sunscreen applied, and the results are closer to linearity than expected by theory.
Claims that substances in pill form can act as sunscreen are false and disallowed in the United States.
In 2019, the FDA proposed tighter regulations on sun protection and general safety, including the requirement that sunscreen products with SPF greater than 15 must be broad spectrum, and imposing a prohibition on products with SPF greater than 60.
In 2021, the FDA introduced an additional administrative order regarding the safety classification of cosmetic UV filters, to categorize a given ingredient as either:
To be considered a GRASE active ingredient, the FDA requires it to have undergone both non-clinical animal studies as well as human clinical studies. The animal studies evaluate the potential for inducing carcinogenesis, genetic or reproductive harm, and any toxic effects of the ingredient once absorbed and distributed in the body. The human trials expand upon the animal trials, providing additional information on safety in the pediatric population, protection against UVA and UVB, and the potential for skin reactions after application. Two previously approved UV filters, para-aminobenzoic acid (PABA) and trolamine salicylate, were reclassified as not GRASE due to safety concerns and have consequently been removed from the market.
I. Cosmetic safety report must be conducted by a qualified personnel
II. The product must not contain substances banned for cosmetic products
III. The product must not contain substances restricted for cosmetic products
IV. The product must adhere to the approved list of colourants for cosmetic products.
V. The product must adhere to the approved list of preservatives for cosmetic products.
VI. The product must contain UV filters approved in Europe.
According to the EC, sunscreens at a minimum must exhibit:
In 2018, Hawaii passed legislation that prohibits the sale of sunscreens containing oxybenzone and octinoxate. In sufficient concentrations, oxybenzone and octinoxate can damage coral DNA, induce deformities in coral , heighten the risk of viral infections, and make corals more vulnerable to bleaching. Such threats are even more concerning given that coral ecosystems are already compromised by climate change, pollution, and other environmental stressors. While there is ongoing debate regarding the real-world concentrations of these chemicals versus laboratory settings, an assessment in Kahaluu Bay in Hawaii showed oxybenzone concentrations to be 262 times higher than what the U.S. Environmental Protection Agency designates as high-risk. Another study in Hanauma Bay found levels of the chemical ranging from 30 ng/L to 27,880 ng/L, noting that concentrations beyond 63 ng/L could induce toxicity in corals.
Echoing Hawaii's initiative, other regions including Key West, Florida, the U.S. Virgin Islands, Bonaire, and Palau have also instituted bans on sunscreens containing oxybenzone and octinoxate.
The environmental implications of sunscreen usage on marine ecosystems are multi-faceted and vary in severity. In a 2015 study, titanium dioxide nanoparticles, when introduced to water and subjected to ultraviolet light, were shown to amplify the production of hydrogen peroxide, a compound known to damage phytoplankton. In 2002, research indicated that sunscreens might escalate virus abundance in seawater, compromising the marine environment in a manner akin to other pollutants. Further probing the matter, a 2008 investigation examining a variety of sunscreen brands, protective factors, and concentrations revealed unanimous bleaching effects on hard corals. Alarmingly, the degree of bleaching magnified with increasing sunscreen quantities. When assessing individual compounds prevalent in sunscreens, substances such as butylparaben, ethylhexylmethoxycinnamate, benzophenone-3, and 4-methylbenzylidene camphor induced complete coral bleaching at even minimal concentrations.
A 2020 study from the journal Current Dermatology Report summarized the situation as the US FDA currently approving only zinc oxide (ZnO) and titanium dioxide (TiO2) as safe ultraviolet filters, and for those concerned with coral bleaching, they should use non-nano ZnO or TiO2 since they have the most consistent safety data.
Risks
Vitamin D production
Measurements of protection
Sun protection factor and labeling
UVA protection
Persistent pigment darkening
SPF equivalence
Star rating system
PA system
Expiration date
Active ingredients
Zinc oxide was approved as a UV filter by the EU in 2016.
p-Aminobenzoic acid PABA 15% (USA), (EU: banned from sale to consumers from 8 October 2009) USA X Padimate O OD-PABA, octyldimethyl-PABA, σ-PABA 8% (USA, AUS) 10% (JP)
(Not currently supported in EU and may be delisted) EU, USA, AUS, JP X Phenylbenzimidazole sulfonic acid Ensulizole, PBSA 4% (USA, AUS) 8% (EU) 3% (JP) EU, USA, AUS, JP X Cinoxate 2-Ethoxyethyl p-methoxycinnamate 3% (USA) 6% (AUS) USA, AUS X X Dioxybenzone Benzophenone-8 3% (USA) USA, AUS X X Oxybenzone Benzophenone-3 6% (USA), 2.2% (body) / 6% (face) EU, 10% AUS, EU, USA, AUS Banned in Hawaii since 2018 - "harmful to coral reefs, fish, and other ocean life" X X Homosalate Homomethyl salicylate 7.34% (EU) 15% (USA, AUS) EU, USA, AUS X Menthyl anthranilate Meradimate 5% (USA) USA, AUS X Octocrylene Eusolex OCR, Parsol 340, 2-Cyano-3,3-diphenyl acrylic acid, 2-ethylhexylester 10% (USA) EU, USA, AUS X X Octinoxate Octyl-methoxycinnamate, Ethylhexyl methoxycinnamate, 2-Ethylhexyl-paramethoxycinnamate 7.5% (USA) 10% (EU, AUS) 20% (JP) EU, USA, AUS, JP Banned in Hawaii since 2021 - harmful to coral X Octyl salicylate Octisalate, 2-Ethylhexyl salicylate 5% (EU, USA, AUS) 10% (JP) EU, USA, AUS, JP X Sulisobenzone 2-Hydroxy-4-Methoxybenzophenone-5-sulfonic acid, 3-Benzoyl-4-hydroxy-6-methoxybenzenesulfonic acid, Benzophenone-4 5% (EU) 10% (USA, AUS, JP) EU, USA, AUS, JP X X Avobenzone 1-(4-methoxyphenyl)-3-(4-tert-butyl
phenyl)propane-1,3-dione, Butyl methoxy dibenzoylmethane,3% (USA) 5% (EU, AUS) EU, USA, AUS X Ecamsule Terephthalylidene Dicamphor Sulfonic Acid 10% EU, AUS (US: approved in certain formulations up to 3% via New Drug Application (NDA) Route) X Titanium dioxide CI77891, TiO₂ 25% (US) No limit (JP) EU, USA, AUS, JP Generally recognized as safe and effective by the FDA X Zinc oxide CI77947, ZnO 25% (US) No limit (AUS, JP) EU, USA, AUS, JP Generally recognized as safe and effective by the FDA. Protects against skin tumors in mice X X 4-Methylbenzylidene camphor Enzacamene, MBC 4%* EU, AUS X Bisoctrizole Methylene Bis-Benzotriazolyl Tetramethylbutylphenol, MBBT 10%* EU, AUS, JP X X Bemotrizinol Bis-ethylhexyloxyphenol methoxyphenol triazine, BEMT, anisotriazine 10% (EU, AUS) 3% (JP)* EU, AUS, JP X X Tris-biphenyl triazine 10% EU, AUS X X Trolamine salicylate Triethanolamine salicylate 12% AUS X Drometrizole trisiloxane 15% EU, AUS X X Benzophenone-n CAS 3121-60-6, Sodium Dihydroxy Dimethoxy Disulfobenzophenone 10% JP Ethylhexyl triazone octyl triazone, EHT 5% (EU, AUS) 3% (JP)* EU, AUS X Diethylamino hydroxybenzoyl hexyl benzoate Parsol DHHB, Uvinul A Plus b 10% EU, AUS, JP X Iscotrizinol diethylhexyl butamido triazone, DBT 10% (EU) 5% (JP)* EU, JP X Polysilicone-15 Dimethico-diethylbenzalmalonate 10% EU, AUS, JP X Amiloxate Isopentyl-4-methoxycinnamate, Isoamyl p-Methoxycinnamate, IMC 10%* EU, AUS X Methoxypropylamino cyclohexenylidene ethoxyethylcyanoacetate 3% EU X
Inactive ingredients
Application
Regulation
Palau
United States
Europe
Canada
ASEAN (Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, Vietnam)
Japan
China
Australia
New Zealand
Mercosur
Environmental effects
Research and development
Note
External links
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