Yale: New Study on the Importance of Controlling Sunscreen Absorption

Sunbaker maxdupain nga76.54

 In a recent study at Yale University, researchers are hopeful they have finally found a new sunscreen doesn’t penetrate the skin, which could eliminate the health concerns associated with it.

While this may sound confusing, given the fact that most people believe sunscreen was intended to be absorbed into the skin, it has came light that some commercial sunblocks can be absorbed too well – into the bloodstream. When a sunscreen is absorbed below the skin surface the next stop is the blood.  As a result, they pose possible hormonal side effects and could even be promoting the kind of skin cancers they’re designed to prevent!

Luckily for those of us with near-zero skin pigment,  researchers have developed a new sunblock made with bioadhesive nanoparticles intended to only stay on the surface of the skin.

“We found that when we apply the sunblock to the skin, it doesn’t come off, and more importantly, it doesn’t penetrate any further into the skin,” says senior author Mark Saltzman, professor of biomedical engineering at Yale University.

“Nanoparticles are large enough to keep from going through the skin’s surface, and our nanoparticles are so adhesive that they don’t even go into hair follicles, which are relatively open.”

In the study, the researchers used mice models to test their new sunblock against direct ultraviolet rays and the sun’s ability to cause sunburn. In this regard, even though it used a significantly smaller amount of the active ingredient than commercial sunscreens, the researchers’ formulation protected equally well against sunburn.

Indirect Effects of UV Light and Sunscreen

Researchers  also looked at an indirect effect of UV light, which is a subject far less studied than the direct effects of UV light.

When the active ingredients of sunscreen absorb UV light, a chemical change triggers the generation of oxygen-carrying molecules known as reactive oxygen species (ROS). If a sunscreen’s agents penetrate the skin, this chemical change could cause cellular damage, and potentially facilitate skin cancer. Odd but true. This  is because the “…commercial chemical sunblock is protective against the direct hazards of ultraviolet damage of DNA, but might not be against the indirect ones,” says coauthor Michael Girardi, a professor of dermatology at Yale Medical School. “In fact, the indirect damage was worse when we used the commercial sunblock.

Girardi, who specializes in skin cancer development and progression, says little research has been done on the ultimate effects of sunblock usage and the generation of ROS, “but obviously, there’s concern there.”

In the past, previous studies have uncovered traces of commercial sunscreen chemicals in users’ bloodstreams, urine, and breast milk. What causes such concern with this is the evidence that these chemicals cause disruptions with the endocrine system, such as blocking sex hormone receptors. However, the researchers new sunscreen was developed to remain only on the surface of the skin, even after water exposure and towel wiping, it must never absorb to deeper skin layers.

Making the Perfect Sunscreen

To make the sunblock, the researchers developed a nanoparticle with a surface coating rich in aldehyde groups, known for their ability to stick to a person’s outer skin layer. The nanoparticle’s hydrophilic layer essentially locks in the active ingredient, a hydrophobic chemical called padimate O.

Some sunscreen solutions that use larger particles of inorganic compounds, such as titanium dioxide or zinc oxide, also don’t penetrate the skin and are commonly found in cosmetic products and makeup.   The Yale team’s use of  nanoparticles to encase padimate O (the organic chemical used in many commercial sunscreens) the Yale team’s sunblock turned out both transparent while staying out of the skin cells and the bloodstream.

The study and the results have been published in Nature Materials.


Image: Sunbaker by Max Dupain, Public Domain

Source: Yale University, Post by William Weir-Yale, CC by 4.0 International

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