Most people today are aware of at least some of the damaging effects that sunlight has on the skin. In addition to painful sunburns, excessive exposure to sunlight can cause sun damage that prematurely ages the skin, causes blemishes, and greatly increases the risk of various types of skin cancer.
Unfortunately, although we know protecting uncovered skin is important, with a large variety of sunscreens, sunblocks, lotions, gels, sprays, mists, and sticks marketed in different strengths and for different purposes, it can be difficult to determine how to best protect yourself.
The Sun’s Damaging Rays
When it comes to avoiding sunburn and sun damage, the form of sunlight we’re most concerned with are invisible waves of ultraviolet light classified as UVA and UVB. UVA and UVB pass through air to the Earth’s surface, and they can even pass through clouds, which is why you can sunburn on a cloudy day.
Approximately 95% of the ultraviolet light that penetrates your skin is UVA. This form is responsible for tanning, penetrates more deeply than UVB, and is an important factor in causing sun damage and skin cancers.
UVB accounts for about 5% of the UV light that strikes your skin. Although UVB doesn’t penetrate as deeply as UVA, it has more energy and is the primary cause of sunburn. Most sunscreens protect against UVB, and fewer protect against both UVA and UVB. The sun protection factor (SPF) rating is a general measure of how well a sunscreen protects against developing a sunburn from UVB.
SPF (Sun Protection Factor)
SPF measures the time it takes to produce a sunburn reaction on protected skin compared to unprotected skin. However, avoid believing you can stay in the sun 10 times longer with SPF 10 sunscreen, because there are misconceptions about SPF and sunscreen.
SPF only measures protection against UVB, and does not measure UVA protection. Also, an SPF 30 sunscreen is not twice as effective as SPF 15. An SPF 15 sunscreen blocks around 93% of UVB; whereas an SPF 30 sunscreen blocks about 97%.
In addition, people generally apply sunscreen more thinly than recommended, which lowers the SPF. Sunscreens claiming to be water-resistant will wash off after about 40 minutes and those claiming to be very water-resistant protect for up to 80 minutes. Certain labels such as waterproof, sunblock, and all-day protection are misleading, and governmental agencies in various parts of the world have recommended banning their use on sunscreen bottles for this reason.
Types of Sunscreen and How They Work
Sunscreens can be classified by how they protect against UV light as well as by the type of UV protection they provide. Sunscreens protect against UV damage by either chemical or physical means, or a combination of both.
Chemical sunscreens are absorbed into the skin and are designed to halt UV before it damages skin. When UV light strikes the sunscreen molecules, absorbed energy excites the molecules, which release the energy as heat as they return to their former state.
Conversely, physical sunscreens act as a protective film on the surface of the skin. UV light that strikes the sunscreen molecules is either absorbed into the sunscreen, or it is scattered and reflected away before passing into the skin.
Most sunscreens protect against UVB, but fewer are what are known as broad-spectrum or full-spectrum sunscreens, which protect against both UVA and UVB. Whether a sunscreen blocks against UVB alone or both UVA and UVB depends on its ingredients.
One of the first ingredients used in modern sunscreens was para-aminobenzoic acid, or PABA. Although PABA protects against UVB, it produces adverse reactions in some people, which is why you will sometimes see PABA-free listed on sunscreen bottles.
Today cinnamates are the most frequently used sunscreen ingredient for UVB protection. Two increasingly common UVA protectants are avobenzone and ecamsule.
Among physical sunscreen ingredients, metallic compounds such as zinc oxide or titanium dioxide are common and protect against UVA and UVB. These metallic, physical sunscreen ingredients are also sometimes blended into chemical sunscreens along with the other chemical ingredients.
Roll over any category on your screen to view lists and alternative names of common sunscreen ingredients used today. You can compare these ingredients with those listed on your sunscreen bottle, or you can look for sunscreens with a particular type of ingredient to give you the protection you desire.
As you may notice when looking at the back of a bottle, sunscreens usually contain a variety of ingredients. Some of them work with other chemicals to increase the SPF, stabilize ingredients to prevent them from breaking down after UV exposure, or to reduce the oily feeling.
Other additives may also be included such as fragrances, softening agents, antioxidants, moisturizers, and even insect repellents. Keep in mind, however, that although some of these products may be convenient, they are not all intended for the same uses.
For example the insect repellent DEET does not need to be applied as frequently as is recommended for sunscreen. If you are going to be in the sun for a period of time that would require several applications, a separate sunscreen and bug repellent may be the best choice.
The Sunscreen Controversy
There is some controversy over sunscreen use. You produce vitamin D as a result of UV exposure, and some people are concerned that sunscreen use may cause a deficiency. However, people have been found to maintain normal vitamin D levels with proper sunscreen use, and those with a deficiency or minimal sun exposure can obtain additional vitamin D in supplements.
Another concern stems from an observation that since sunscreen protects from the UVB rays that cause sunburn, people stay in the sun longer, potentially increasing the chance of developing melanoma skin cancers from UVA exposure. To reduce this risk, use a sunscreen with UVA protection.
Proper Sunscreen Application and Use
Dermatologists recommend using a broad-spectrum sunscreen of SPF 15 or greater. Apply the amount recommended on the sunscreen bottle fifteen to thirty minutes before sun exposure.
Shake the bottle well and remember to apply sunscreen to frequently forgotten areas such as the ears, back of the neck, bridge of the nose, scalp, hands, and feet. Reapply sunscreen every two hours or when done toweling off after swimming.
Sunscreen is just one way to protect yourself from the sun. In addition, try to avoid sun exposure between the hours of 10:00 A.M. and 2:00 P.M. when the sun is most intense. When possible, wear long sleeved shirts and pants, and wear a wide-brimmed hat to protect your head and neck.
Infants under 6 months of age have particularly thin, sensitive skin and should be shielded from the sun. Since children often receive much more sun exposure than adults but tend to dislike sunscreen, a variety of physical sunscreens now come in exciting colors and packaging to make them more appealing.
Choosing the Right Sunscreen
Always opt for a broad spectrum sunscreen that protects against both UVA and UVB. Physical sunscreens generally offer the best sun protection, but they are often visible on the skin. As a remedy, some sunscreens reduce the size of the zinc oxide and titanium dioxide ingredients to avoid visible residues.
Determining the correct SPF to use depends on how susceptible you are to burning and the amount of time you plan to spend in the sun. The effectiveness of your sunscreen will depend both on how well you apply it and the protective ingredients in the sunscreen.
If you find that your skin is sensitive to a specific ingredient or sunscreen additive, or if you don’t like the way the sunscreen feels on your skin, you can use what you now know about sunscreens to find a different formulation that will suit your needs.