Sunscreen
Sunscreen, also known as sunblock, sun lotion or sun cream, is a photoprotective topical product for the skin that helps protect against sunburn and prevent skin cancer. Sunscreens come as lotions, sprays, gels, foams, sticks, powders and other topical products. Sunscreens are common supplements to clothing, particularly sunglasses, sunhats and special sun protective clothing, and other forms of photoprotection. Sunscreen is on the World Health Organization's List of Essential Medicines.
Sunscreen products may be classified according to the type of active ingredient present in the formulation as:
- Mineral sunscreens, which use only inorganic compounds as active ingredients. These ingredients primarily work by absorbing UV rays but also through reflection and refraction.
- Chemical sunscreens, which use organic molecules as active ingredients. Chemical sunscreen ingredients work by absorbing the UV rays. Additionally, particulate organic UV filters, such as bisoctrizole, can also reflect and scatter a small portion of incident UV light.
- Hybrid sunscreens, which contain a combination of organic and inorganic UV filters.
History
Early civilizations used a variety of plant products to help protect the skin from sun damage. For example, ancient Greeks used olive oil for this purpose, and ancient Egyptians used extracts of rice, jasmine, and lupine plants whose products are still used in skin care today. Zinc oxide paste has also been popular for skin protection for thousands of years. Among the nomadic sea-going Sama-Bajau people of the Philippines, Malaysia, and Indonesia, a common type of sun protection is a paste called borak or burak, which was made from water weeds, rice, and spices; it is used most commonly by women to protect the face and exposed skin areas from the harsh tropical sun at sea. In Myanmar, thanaka, a yellow-white cosmetic paste made of ground bark, is traditionally used for sun protection. In Madagascar, a ground wood paste called masonjoany has been worn for sun protection, as well as decoration and insect repellent, since the 18th century, and is ubiquitous in the Northwest coastal regions of the island to this day.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. The link between UV rays and skin burns was established experimentally by Erik Johan Widmark in 1889, which initiated research into substances capable of blocking or absorbing UV radiation for skin protection.
The first commercial sunscreen was under the names Zeozon for sunburn prophylaxis and Ultrazeozon against glacier burn from Kopp & Joseph produced with aesculin derivatives.
Once Wilhelm Hausser and Wilhelm Vahle had determined the wavelength responsible for sunburn on the skin at 297 nm, all that remained was to find substances that absorb in this specific wavelength range.
It was Emil Klarfeld who identified two substances Salicylicacidbenzylester and Benzylcinnamic acid ester that absorb in the requested range. He formulated a product with these two ingredients and the company Lehn & Fink launched the product under the Dorothy Gray brand.
Followed by the first sunscreen, invented in Australia by chemist H.A. Milton Blake, in 1932 formulating with the UV filter Tannic acid at a concentration of 10%. Its protection was verified by the University of Adelaide. Research into new products continued unabated in the 1930s. In Germany, the physicist Erich Merkel and his colleague Christian Wiegand, a chemist, wanted to find out whether it was possible to form pigment on human skin through solar radiation without sunburn. They thought that a substance that absorbs between 320 nm and 290 nm should prevent the skin from reddening but allow the tanning rays to pass through. Merkel and Wiegand worked at IG Farben in the physics laboratory in Elberfeld. Merkel tested the first filter substances identified by Wiegand in practice. He climbed Corvatsch and the Jungfraujoch to do this. The experiments were encouraging. Now the researchers tested their further developments on female employees in the laboratory. They stuck jars of the substances on their backs, forearms, or thighs and measured the effect; novantisolic acid turned out to be the best candidate. The substance was patented as a sunscreen protection agent in Germany in 1933 and a year later in the United States. IG Farben founded a subsidiary, Drugofa, with the aim of launching a product with the active ingredient on the market under the name Delial.
In 1936, L'Oreal released its first sunscreen product, formulated by French chemist Eugène Schueller.
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 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, Austrian chemist Franz Greiter introduced a product, called Gletscher Crème, subsequently became the basis for the company Piz Buin, named in honor of the mountain where Greiter allegedly received the sunburn.
In 1974, Greiter adapted earlier calculations from Friedrich Ellinger and Rudolf Schulze and introduced the "sun protection factor", 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, more environmentally friendly, more appealing to use, and addressing the safety concerns of petrochemical sunscreens.
Health effects
Benefits
Sunscreen use can help prevent melanoma and squamous cell carcinoma, two types of skin cancer. There is little evidence that it is effective in preventing basal cell carcinoma.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 white 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 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.
Risks
In February 2019, the US Food and Drug Administration started classifying already approved UV filter molecules into three categories: those which are generally recognized as safe and effective, those which are non-GRASE due to safety issues, and those requiring further evaluation. As of 2021, only zinc oxide and titanium dioxide are recognized as GRASE. Two previously approved UV filters, para-aminobenzoic acid and trolamine salicylate, were banned in 2021 due to safety concerns. The remaining FDA-approved active ingredients were put in the third category as their manufacturers have yet to produce sufficient safety data — Pending further safety data, several FDA-approved active ingredients remain under evaluation. Some researchers argue that the risk of sun-induced skin cancer outweighs concerns about toxicity and mutagenicity, although environmentalists say this ignores "ample safer alternatives available on the market containing the active ingredient minerals zinc oxide or titanium dioxide", which are also safer for the environment.Regulators can investigate and ban UV filters over safety concerns, 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. 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 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."