Sunscreens absorption - what you need to know.

Do sunscreens get absorbed into our body?

Yes and No.

In this post, let us break down what data and studies we have – in support of both No and Yes.

We call the active agents in your sunscreen product as sunscreen filters or UV filters– these are the heavy lifting ingredients that provide us with the actual UV protection. These may occupy up to 40% of the product, but more commonly, a lower proportion.

Chemical UV filters are mostly lipophilic [lip-uh-fil-ik] agents. Lipophilic means oil loving or oil based. And the skin allows lipophilic agents to get absorbed through the outer layer to enter the deeper layers. This is a principle that is commonly used in dermatology, typically with moisturisers. We really want the moisturiser to enter the skin and travel to the deeper layers. However, we do not want this deeper penetration with sunscreens – for 2 reasons. The first is that sunscreens need to stay on the skin to continue to protect (unlike moisturisers and actives which need to go deeper into the skin to do their job). And the second reason is the one, that is making news now. That sunscreens just don’t get absorbed into the deeper layers of the skin, but that they also get drawn into the bloodstream.

How did we know about this?

Multiple studies have demonstrated that UV filters like benzophenone-3 have been detected in more than 90% of humans exposed to them – the proof being that this filter was identified in multiple bodily fluids including urine and breastmilk. The earliest serious human study was from Denmark in  2008, but what really took the world by storm was the FDA study in 2019/2020. While the Denmark study remained unknown except to serious researchers, social media took the FDA study world over.

So what did the FDA study show?

It showed that on maximal application, sunscreens based on BP-3 (benzophenone/ oxybenzone), octinoxate, homosalate, octisalate, avobenzone and octocrylene, were all found to be absorbed into the bloodstream, much above threshold levels in the body. I will break down the details of this study in an upcoming post for you. But for now, this study, commissioned by the FDA, led to a number of revisions and regulations about the levels of these sunscreen filters that has been allowed until then.

Is it a problem that stuff that we apply on the skin, gets into our body?

Yes and no – it is natural for molecules to make their way into out bloodstream. For example, in newborn care, specific lipids are applied to the skin of preterms which then get absorbed and help the baby gain weight! However, what matters is how these molecules interact with our cells. That makes the difference, towards problems or otherwise. Even though there have been plenty of studies in the past talking about how certain sunscreen filters interact with organ systems, most of these studies were done at very high levels of exposure, and mostly in animal studies. In fact, one researcher stated that it may take upto 250+ years for benzophenone in humans, to be relevant in the same way as animal studies.

So what has changed?

In recent years, think last 5 years, clinical studies have been rolling in about how exposure to certain chemical UV filters, notably, BP-3 aka oxybenzone, and octocrylene can put a person at risk of certain diseases/ conditions. So the exposure problem has now moved out of the lab, out of animal research, out from being an ecological risk, to becoming an actual risk in everyday life. And therefore, UV filter absorption, and its subsequent interaction with human tissue, has now become a clinically relevant, mainstream problem.

Still, the risk is not acute – we just need to not rely on the same filter all our lives, and potentially move to the newer chemical filters, or the best case, mineral filters.

Are mineral sunscreens not absorbed then?

Correct. Zinc oxide and titanium dioxide, the 2 mineral sunscreens currently available, do not have any level of absorption into the bloodstream. In fact, zinc is not even absorbed into the living layers of the skin. (Titanium nanoparticles though, have been found in the placenta but the thought is that this could have come from titanium in food additives (intake), or sunscreen sprays (inhalation), rather than through the skin.) Further, the safety profile of zinc is very high, since we have all taken zinc supplements over the years, without any harm, unlike the older chemical filters.

Newer larger chemical filters like bemotrizinol, bisoctrizole and polysilicone 15, are also too large to get absorbed easily, beyond background threshold limits.

So, instead of blanket rejecting all sunscreens as capable of being absorbed into the body, you can specifically avoid certain filters which have been red flagged by research. Our research team has helped put together a simple sunscreen ingredient checker, to see which sunscreen filters have been shown to get absorbed. I have explored this aspect of sunscreens in more detail in academic book on Sunscreens in Skin of Color, out now. 

Very ironically, a key factor that drives sunscreen absorption into your body, is … sunscreen reapplication. We will explore that soon.