Sunscreen Effects Are More Than Skin Deep

By Contributing Writer - June 11, 2019

Some sunscreens can get under your skin, but that’s no reason to abandon the daily ritual. So says a Moffitt Cancer Center physician and researcher specializing in the prevention and treatment of skin cancer.

A recent study published in the Journal of the American Medical Association showed that the active ingredients in some sunscreens can soak through the skin and into the user’s bloodstream. The study enlisted 24 healthy volunteers who were assigned one of four sunscreens with different active organic ingredients: avobenzone, oxybenzone, octocrylene and ecamsule.  Participants were told to apply them over at least 75% of their body four times daily over the course of four days. Blood samples drawn throughout the study showed significant amounts of the active ingredients in participants’ blood within one day. The amounts continued to grow throughout the four days, accumulating with continued use.

Dr. Kenneth Tsai
Dr. Kenneth Tsai Melanoma and Skin Care Center of Excellence

Dr. Kenneth Tsai of Moffitt’s Melanoma and Skin Cancer Center of Excellence says the fact that these active ingredients get into the bloodstream is not news. “We’ve known for a long time that it can be absorbed into the bloodstream, with traces appearing in urine or breast milk,” said Tsai. What’s new is how much appeared in the blood within a day – over 0.5 nanograms per milliliter of blood. That’s enough to trigger further testing under a proposed rule from the Food and Drug Administration.

“It’s reasonable to study this data and the issue more in-depth to understand the possible implications on cancer risks, birth defects or other adverse events,” said Tsai, “but it’s not enough reason to stop using sunscreen altogether.”

Tsai says it’s important to remember that the study participants were probably doing a much better job of applying and re-applying than the average person does, which may partially account for the absorption amounts.

For those who are concerned, Tsai suggests alternatives including sunblocks like zinc oxide or titanium dioxide. They may not be as cosmetically attractive as sunscreens that disappear into the skin. But that’s the point: these inorganic compounds are not absorbed, instead sitting atop the skin to reflect damaging rays.  And as for homemade sunscreens touted widely in recent social media posts, Tsai says there is no way to judge their effectiveness or safety.

“Sunscreen or sunblock are not panaceas,” said Tsai, “but rather part of a comprehensive approach to being smart about UV light exposure.” Among his suggestions:

  • Avoid midday sun exposure (10AM – 3PM)
  • Wear a hat, long sleeve shirt, long pants, rash guard and/or other clothing items with UV-protection ratings
  • Eliminate use of tanning beds

Suffice it to say, Tsai hopes further study will be done to determine these sunscreen ingredients’ safety.  “Our patients need us as clinicians to be able to recommend products that have gone through rigorous testing and have an established track record of safety,” said Tsai.  In the meantime, remember that UV light is a carcinogen, and excessive sun exposure is the single greatest environmental risk factor for developing skin cancer. It also accelerates skin aging.  So take alternative measures to protect yourself.


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