Health Benefits of Sunscreen 28-06-2020

For glowing skin in summers, you need something more than sunscreen

Sunscreen, also known as sunblock, is a lotion, spray, gel, foam (such as an expanded foam lotion or whipped lotion), stick, or other topical product that absorbs or reflects some of the sun's ultraviolet (UV) radiation and thus helps protect against sunburn. Diligent use of sunscreen can also slow or temporarily prevent the development of wrinkles, dark spots, and sagging skin.

Depending on the mode of action, sunscreens can be classified into physical sunscreens (i.e., zinc oxide and titanium dioxide, which stay on the surface of the skin and mainly deflect the UV light) or chemical sunscreens (i.e., UV organic filters, which absorb the UV light).

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. However, many sunscreens do not block UVA (UVA) radiation, yet protection from UVA is important for the prevention of skin cancer. The sun's rays have two types of UV rays: UVA and UVB. UVA rays penetrate your skin more deeply than UVB and are the reason for premature skin aging. UVB rays are the primary sunburning culprits. You need to use a sunscreen because it protects your skin from UV damage and sunburn. Sunscreens are over-the-counter products in some countries that come in lotions, gels, ointments, and sprays. The strength of the sunscreen protection is measured as an SPF or sun protection factor.

To provide a better indication of their ability to protect against skin cancer and other diseases associated with UVA radiation (such as phytophotodermatitis), the use of broad-spectrum (UVA/UVB) sunscreens has been recommended. The use of the term "Broad Spectrum" on the label sunscreen products is regulated by the U.S. Food and Drug Administration.

Sunscreens are commonly rated and labeled with a sun protection factor (SPF) that measures the fraction of sunburn producing UV rays that reach the skin. For example, "SPF 15" means that ¹⁄₁₅ of the burning radiation reaches the skin through the recommended thickness of sunscreen. Other rating systems indicate the degree of protection from non-burning UVA radiation.

Sunscreens are designed to remain effective at original strength for up to three years, and are typically of doubtful value after that period. Some sunscreens include an expiration date a date indicating when they are no longer expected to be effective.

What is SPF?

We are often confused to varying degrees when it comes to choosing a sunscreen because of multiple choices in the market and more importantly, because we are not sure what should our choice be based upon? How high should the sun protection factor (SPF) be? Should it block UVA or UVB? Should it be particular a gel, a cream, or a spray? Should it be water-resistant or waterproof?

The SPF of a sunscreen product determines how efficiently it absorbs or reflects some of the sun’s ultraviolet (UV) radiation on the skin exposed to sunlight. It is a measure of protection against mainly UVB rays, the ones that cause sunburn. The higher the SPF number, the greater the protection.

Solar ultraviolet radiation (UVR) is divided into three categories: UV-C (200-280 nm), UV-B (280-320 nm) and UV-A (320-400 nm). UV-C is the most biologically damaging radiation, but it is filtered out by the ozone layer. Currently, UV-B radiation and to a lesser extent UV-A radiation are responsible for inducing skin cancer. Sunscreens and sunblocks are chemicals that absorb or block UV rays.

SPF is a measurement of the time it would take for a person to start getting burns (redness of skin) if he or she was not wearing sunscreen. In general, it takes about 10 to 20 minutes without sunscreen for a person’s skin to start burning. An SPF 15 product would prevent skin from burning for 15 times longer so about 300 minutes, or about five hours. However, that doesn’t mean that full protection is obtained for those five hours. Dermatologists highly recommend reapplying sunscreen every two to four hours, as sunscreen can rub off or get washed off in the water or by sweat.

SPF testing

There are two methods of SPF testing in vivo (in human volunteers) and in vitro (in laboratory). Though desired, In vivo SPF testing, as of now, has several drawbacks. This evaluation method is expensive in terms of money and time. It also gives rise to several ethical issues concerning the potential damage to the skin of volunteers who participate in SPF testing.

There are several in vitro techniques that have been developed. In vitro SPF testing generally consists of a film of sunscreen applied to an artificial test substrate and a spectrophotometer which analyzes the amount of UVR passing through the film of product.

An in vitro SPF testing method is advantageous as it can generate results faster and cheaper. Furthermore, it can also avoid the ethical concerns associated with in vivo SPF testing.

However, it needs a great amount of standardization and controls to achieve reproducible and reliable results.

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 can 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.

Minimizing UV damage is especially important for children and fair-skinned individuals and those who have sun sensitivity for medical reasons.

Potential risks

In 2009, the Therapeutic Goods Administration of Australia updated a review of sunscreen safety studies and concluded: "The potential for titanium dioxide (TiO₂) and zinc oxide (ZnO) nanoparticles in sunscreens to cause adverse effects depend primarily upon the ability of the nanoparticles to reach viable skin cells. To date, the current weight of evidence suggests that TiO₂ and ZnO nanoparticles do not reach viable skin cells. Sunscreen ingredients typically undergo extensive review by government regulators in multiple countries, and ingredients that present significant safety concerns (such as PABA) tend to be withdrawn from the consumer market.

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."

Vitamin D production

Concerns have also been raised about potential vitamin D deficiency arising from prolonged use of sunscreen. Typical use of sunscreen does not usually result in vitamin D deficiency; however, extensive usage may. Sunscreen prevents ultraviolet light from reaching the skin, and even moderate protection can substantially reduce vitamin D synthesis. However, adequate amounts of vitamin D can be produced with moderate sun exposure to the face, arms, and legs, averaging 5–30 minutes twice per week without sunscreen. (The darker the complexion, or the weaker the sunlight, the more minutes of exposure are needed, approximating 25% of the time for minimal sunburn.) Vitamin D overdose is impossible from UV exposure thanks to an equilibrium the skin reaches in which vitamin D degrades as quickly as it is created.

These earlier studies were confirmed in 2019 which showed 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.