Sunscreens work by absorbing (organic sunscreens), or reflecting and scattering UV light (physical sunscreens).

SPF stands for Sun Protection Factor. It is the measure of UVB protection offered by a product and ranges from 2 to 80. The number correlates with how long that sunscreen will protect you from the sun before you start to burn. It is a confusing measurement: An SPF of 60 does not give you twice as much protection as an SPF of 30. In today’s world it more accurately reflects what percentage of the sun’s rays are blocked for as long as the sunscreen is working. Since most sunscreens need to be reapplied every 2 hours, we view SPF as a useful but not definitive measure. For instance, an SPF of 30 will block 97% of the sun’s UVB rays, while an SPF of 50 will block 98%. Not twice the protection, especially since it must be reapplied. And SPF does not take into account UVA protection, which is another issue.

Solar radiation consists of a continuous spectrum of wavelengths that reaches the earth’s surface. In sun damage, we are concerned with UVA, UVB and UVC. They are all at the end of the visible light spectrum (Red, Yellow, Blue, Purple, etc.).

Ultraviolet radiation is described as UVA, UVB and UVC rays. The UVA region of the UV spectrum extends from 320nm to 400nm (a measure of the size of the light wave).

UVA is thought to contribute to photoaging (lines, brown spots and wrinkles) and is also thought to play an adjunctive or auxiliary role in the creation of skin cancers.

The UVB rays produce sunburn, skin cancer and photo aging. Their spectrum is 290 nm to 320 nm.

The UVC region of the UV spectrum extends from 200nm to 290nm. UVC is absorbed by the ozone layer of the stratosphere and does not reach the surface of the earth. This may change with the depletion of the ozone layer and UVC may become more important as time goes on.

First, although we always recommend a high SPF for our patients, the use of sunscreens is more complicated than that. An SPF 15 protects against 93% of UVB rays, SPF 30 from 97%, and SPF 50 from 98%. So you do not double your protection by doubling the SPF. The difference in sunscreens of similar SPF’s has to do with the presence of varying active and inactive ingredients. The active ingredients are what protect you from the sun. The inactive ingredients are what give a particular sunscreen its characteristics: water resistant, non-pore clogging (non-comedogenic), etc.

You would need to live inside a cave without any light to get complete sun protection. And you should not try it. Vitamin D and many other processes, such as hormonal regulation, depend upon exposure to natural sunlight. Practicing safer fun in the sun should balance the body’s natural need for sun exposure, your psychological need for sunshine, your physical need to be outdoors with a thoughtful protection plan to minimize your chances of sun damage by employing only dermatologist recommended sunscreens.

The interactions in marine biology are so complex that it is impossible to say for sure what effects the numerous chemicals in the environment have on the marine environment and specifically on coral reefs. MDSolarSciences seeks to eliminate any sunscreen actives or additives that have been implicated, such as octinoxate, Our philosophy is that if we can do without it, it is better to leave it out, especially if there is any question.

No since 80% of UV radiation can pass through the clouds. Some of the worst burns occur on cloudy days because we think we are not being exposed to the sun.

It is probably better to avoid the intense sun in children less than 6 months of age. Although sunscreens may be better than nothing, the unknown allergic potential of infants, the unknown safety and absorption of many of the active and inactive ingredients makes it safer to just use sun protective clothing, hats and good sun avoidance. We recommend you ask your pediatrician for guidelines.