Does Sunscreen Cause Cancer?

Melanoma, one of the rarer types of skin cancer, causes the majority of skin cancer related deaths. Its incidence has increased steeply since the mid-1970s. Rising trends have continued since the 1970s and 1980s, when sunscreens with high sun protection factors (SPF) became widely used. At the beginning, people suspected that sunscreens damaged the skin and increased the skin cancer rate. But fortunately researchers found out the true reason.

Commonly used sunscreens block UVB but are virtually transparent to UVA, which makes up to 90 to 95% of ultraviolet energy in the solar spectrum. By blocking UVB, sunscreens reduce tanning and prevent sunburn. On one hand, tannning and sunburn are skin damage of certain levels. On the other hand, they are, to some extent, skin’s natural accomodation to sunlight. Sunscreens that block UVB prevent this process and thus may permit excessive exposure of the skin to UVA. And then the damage resulting from UVA is greater. This is the true reason why the incidence rate of the skin cancer has risen with the use of sunscreens.

Another reason is perhaps the change of people’s patterns of recreational sun exposure. By using sunscreens, people think they are protected and do not feel the need to avoid sunlight in other ways. If the sunscreens they use only block UVB, this makes matters much worse.

Please be clear that the solution is NOT stop using sunscreens. Melanoma is only one type of skin cancer and there are many more problems caused by UV. By telling the above story, I hope that everyone realizes how important it is to use sunscreens with UVA protection as well.

Please do remember that SPF is an imperfect measure (see Sunscreen Basics). The SPF indicates the amount of UVB radiation that can reach your skin before the skin burns, not considering UVA at all. Before FDA comes up with a new measure including the effects of UVA, what you can do is to check whether the active ingredients of your sunscreens include avobenzone (also called butyl methoxydibenzoylmethane), zinc oxide, titanium dioxide, or Mexoryl SX (also called ecamsule). Outside US, Tinosorb S (also called bis-ethylhexyloxyphenol methoxyphenyl triazine) and Tinorsorb M (also called methylene bis-benzotriazolyl tetramethylbutylphenol) are also approved.

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