Tough Questions about Sunscreens
How important is SPF? Is more always better? Why do I see the same sunscreen of the same brand with different SPFs?
SPF measures a sunscreen´s ability to protect against UVB light, one of the two spectrums of UV light that we are exposed to. The number is supposed to express the difference in the length of time that it takes for a person´s skin to become burned with sunscreen and without sunscreen under laboratory conditions. High SPF is good, but there are a few caveats which may help answer your questions:
- SPF 30 blocks 97% of UVB light. Above this level, diminishing returns are amplified. Blocking another 1% of UVB is unlikely to be of much significance.
- SPF is measured under laboratory conditions that are unrealistic. Most people use a fraction of the recommended use - about three table spoons every two hours - thus not getting the sun protection that the label suggests. Similarly, water, wind, sweat, and towelling all reduce the sunscreen´s efficacy in actual use. This suggests that a higher SPF may actually have some marginal benefits.
- UV light erodes sunscreens quickly. Reapplication is more important than the SPF number after a certain point.
- Many of the actives in sunscreen ingredients leave a thick and heavy consistency or a white color on the skin. Higher SPF products may have a larger concentration of these actives, which some people may not like.
- Generally, you would do well to use a sunscreen with a minimum SPF of 15. Always choose sunscreens that provide broad spectrum protection - they protect you from both UVB and UVA rays. SPF only measures protection from UVB light.
- Remember that personal preference and cost of the sunscreen are also important factors that shouldn´t be ignored. If you don´t like your sunscreen, you are much less likely to use it on a regular basis. Consistency of use is very important.
There is much news about the increase in melanoma incidence. This is recent news, after the concept of sun protection and the use of sunscreens have become popular. Doesn´t this suggest that sunscreens are to blame?
Melanoma incidence has increased at an alarming rate. Blaming sunscreens for this phenomenon, however, is misguided. Correlation does not equal causation. A smaller percentage of people smoke in recent years compared to 20 years ago due in part to increased public awareness of the dangers of smoking. It would be misguided to suggest that smoking must be good for preventing melanoma because there are higher incidences of melanoma in recent years. There is substantial evidence that suggests the overall benefit in the use of sunscreens in reducing skin cancers including melanoma.
- Correlation does not imply causation. There are many factors that influence melanoma incidence, some of which we don´t yet understand. We should not be hasty in pinning the blame on one factor due to correlation.
- There is substantial evidence that supports the causal relation between UV damage and melanoma, as well as other skin cancers. UV radiation is a class 1 carcinogen - known to cause cancers.
- The efficacy of sunscreens in blocking a large percentage of UVA and UVB light when appropriately used has been established through many trials.
- Medical advancements in the area of screening and identification have improved significantly in recent decades. Many previously undiagnosed cases of melanoma are now being diagnosed.
- For older generations, the sun damage that triggered melanoma may have been caused long ago when sunscreens were less popular.
- Ozone depletion may also be a factor in increased UV exposure in general.
- Healthy skepticism is important in protecting yourself but remember to weigh the evidence appropriately.
What about vitamin D? Isn´t the sun important for life? Have we gone too far in vilifying the sun? Aren´t tans healthy?
The sun is indeed important for all life on earth. UVB allows our body to produce vitamin D, and extreme and excessive avoidance of sunlight can cause vitamin D deficiency unless the vitamin is obtained through diet or supplements. For some people, lack of sunlight is considered to be one of the causes of seasonal affective disorder, a type of mood disorder related to seasonal depression. Sunlight is unique in being a carcinogen that also has health benefits.
It is important to have balance, and the dermatological community isn´t trying to vilify the sun. It is also important to remember that there is an enormous amount of research that documents the type of damage that UV rays have on human health. For most people, and especially for those with lighter skin tones, the weighted balance of evidence suggests that we should be protecting ourselves from the sun more than we currently are.
- UV radiation is thought to be a major contributing factor in up to 8000 deaths from melanoma in the United States alone. It is a class 1 carcinogen - known to cause cancer. It is also responsible for causing non-melanoma skin cancers.
- UV damage accumulates over the years, causing cosmetic changes such as wrinkling, dryness of the skin, and leathery textures, as well as pigmentation problems. All of these symptoms are generally associated with premature aging.
- People with lighter skin color absorb sunlight much more readily compared to those with dark skin. 10 minutes of incidental sun exposure a week is adequate to produce the necessary vitamin D for lighter skinned individuals, and this amount of sun exposure occurs while driving, or commuting to work for the overwhelming majority of people.
- Vitamin D can be obtained through diet. Many products such as milk or juice are vitamin D fortified. Foods like salmon and mackerel naturally contain high levels of vitamin D.
- Tans are not healthy in any way. Tans are the result of activated melanocytes, and are evidence of sun damage.
- Balance is indeed important. Complete avoidance of sunlight is in fact unhealthy. Generally, we are still far on the side of overexposure, and this is showing in the high incidence of skin cancer, other forms of sun damage, and premature aging and thus the need for education about the effects of sunlight continues.