Sunscreens have been around for nearly 100 years. The goal was to block ultraviolet (UV) light, the harmful rays of the sun. Sunscreens started out with pasty zinc oxide that no one would use. So scientists created sunscreens with clear chemicals that absorbed UV light. In 1944, Coppertone® became the first mass marketed sunscreen. Fast forward to now, when about a billion dollars worth of sunscreen are sold each year in the United States.
UV light causes skin cancer and prematurely ages the skin, and so it’s very important to protect our skin with sunscreen. We don’t want to block sunshine completely – about 20 minutes each day is good for us – it boosts our vitamin D and improves our mood. Beyond 20 minutes, however, and our immune system suffers. We either need to spend the rest of the day inside or protect our skin with sunscreen.
There are 17 individual sunscreen ingredients that are FDA approved: 15 of these are clear chemicals that absorb UV light and two are made of minerals that reflect UV light. Of these 15, nine are known endocrine disruptors. To be effective, chemical sunscreens need to be rubbed into their skin 20 minutes before sun exposure. They do a pretty good job at blocking UV light, but they actually get used up as the sun shines on them. In fact, some sunscreens lose as much as 90% of their effectiveness in just an hour, so they need to be reapplied often. This is not the case with zinc oxide and titanium dioxide, the two mineral, or physical, sunscreens. These two work very differently – they sit on the surface of the skin and physically block UV light.
Chemical sunscreens don’t sit on the surface of the skin – they soak into it and quickly find their way into the bloodstream. They scatter all over the body without being detoxified by the liver and can be detected in blood, urine, and breast milk for up to two days after a single application. That would be just fine if they were uniformly safe – but they’re not.
As I mentioned, nine of the 15 chemical sunscreens are considered endocrine disruptors. Those are chemicals that interfere with the normal function of hormones. The hormones most commonly disturbed are estrogen, progesterone, testosterone, and thyroid. Endocrine disruptors, like some ingredients in chemical sunscreens, can cause abnormal development of fetuses and growing children. They cause early puberty and premature breast development in girls, and small and undescended testicles in boys. They cause low sperm counts and infertility. Endocrine disruptors that act like estrogen can contribute to the development of breast and ovarian cancers in women, and other endocrine disruptors may increase the chance of prostate cancer in men.
Sounds pretty unsettling, doesn’t it? But there’s more. As I said earlier, chemical sunscreens function by absorbing UV light. In the process, some may get used up and mutate. Some generate DNA-damaging chemicals called “free radicals.” These may lead to cancers.
I’m pretty negative about chemical sunscreens, and while I do have to tell you that I believe they are not proven to cause cancer, as I said on The Dr. Oz Show, “Where there’s smoke, there’s fire.”