The sun emits several wavelengths of light. When discussing the effects of sunlight on the skin, one is oftentimes speaking about Ultraviolet B (UVB) and Ultraviolet A (UVA). Currently, it is thought that UVB (wavelengths of 280-315 nm of light) is responsible for contributing to the formation of most skin cancers, sunburns, and, in excessive amounts, temporary immunosuppression. UVA (wavelengths of 315-400 nm of light) penetrates deeper into the skin, and damages collagen, causing wrinkling and a leathery change to the appearance of the skin. For these reasons, it is best to use a broad-spectrum sunscreen, in other words, a sunscreen that screens out much of the UVA and UVB.
Sunscreens absorb or reflect ultraviolet light. They can minimize the amount of visible sun damage and can help to delay or prevent the onset of certain skin cancers, wrinkles, and sagging skin. If using a sunscreen, it is best to employ one that blocks both UVA and UVB—these are called “broad spectrum” sunscreens.
In the United States, the term “spf” is used to indicate the level of protection that a sunscreen product provides. For example, a sunscreen labeled “SPF 30” indicates that with proper use, a person can remain in the sun 30 times longer before redness occurs as compared with no sunscreen. As an example, if it takes 20 minutes for your skin to turn red without sunscreen, it should take 600 minutes (10 hours) before your skin would turn red if you have applied an SPF 30 sunscreen. (20 minutes x 30 = 600 minutes, or 10 hours)
The following is a list of some of the current concerns about sunscreens:
- Some sunscreen ingredients may be estrogenic, in other words, may convert to estrogen-like compounds in the skin.
- Some sunscreen ingredients may be carcinogenic, i.e. convert to carcinogens in the skin.
- Millions of tons of sunscreens are shed by our skin into seawater every year, resulting in the death of sea corals and the sea life that inhabit or eat corals.
- Although UVB protection (the spf of a sunscreen) is measured by testing a sunscreen on humans, UVA protection is measured in a laboratory using light meters or photometers.
- When sunscreens are tested on human subjects, the sunscreen is applied in a thick, visible layer…similar to frosting a cake. This testing method is not similar to actual use.
- Sunscreens are water-resistant, not waterproof. Therefore, they should be re-applied once leaving the water.
- Sunscreen manufacturers pay money to certain organizations so that the manufacturer can obtain a “seal of recommendation” for their products. Many experts in the field of dermatology feel that this is a conflict of interest.
If you find that these controversies, unanswered questions, and problems are of concern to you, may we suggest use of sun-protective clothing instead? One would then only need to apply sunscreen to the exposed skin.