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When Sunscreen is found in your blood…

May 12, 2019

So earlier this week the US Food and Drug Administration released this summary of some fascinating research they had recently concluded.  The full study report can be found here. 

If, after reading that report you feel like your only option is to say ‘fcuk it, I’m going out like this from now on’ I understand.

Fat Lady

Sun Hongbin ‘Fat Lady’ 2012 as seen at the White Rabbit Gallery.

However, hold tight, and we’ll see if there is any light at the end of this tunnel.

The FDA study focused on how four sunscreen actives were adsorbed through the skin when four different sunscreen products were applied using a ‘maximum use’ protocol.   The shorthand for this type of trial is  MUsT (Maximum Usage Trial) and in the USA, this type of test is essential for topical medicines.  Up to now sunscreens have not been required to   produce information with regards to this because the Sunscreen industry has indicated that these products are designed not to absorb. It looks like the FDA finally called ‘bullshit’ on that.  Good.

So what I’m going to do now is give my thoughts on what I’ve read.  My thoughts are formed on a) personal bias in using and choosing sunscreens – this constitutes my opinion b) my volunteer practical hands-on experience of testing sunscreens (Via APTF in Australia with Gavin Greenoak (R.I.P)  c) My experience in buying, selling and marketing of a range of sunscreen actives into the Australian market between 2004-2007 and d) my own sunscreen development work  and consulting research on behalf of my  clients (2007-present day).



When it comes to global sunscreen regulations I like the FDA the best (opinion).  I like the way they are slow and steady and I love how they don’t bend to the whims of individual manufacturers.  I am not convinced that this is the case in Europe (opinion based on my interpretation of what I’ve seen professionally).

So what happened?

This small, scene-setting study ran by the FDA (which in its self is quite unusual as they usually just report on things) showed that we (the cosmetic industry) may have been suffering from denial or misplaced optimism when it comes to sunscreen active absorption.  Now I know that some of you readers like to jump to the ‘OMG I’m going to die’ conclusion but I don’t, instead I’m going to focus first on the fact that sunscreen doesn’t work if it is in your blood…

The study basics.

24 people (men and women) were split into 4 groups and tested 4 different sunscreens (spray, spray, lotion, cream) over 4 days, applying it to 75% of body surface area at the recommended 2mg per Cm2 as per industry guidelines.  As sunscreens are tested this way, you are unlikely to reach the pack SPF if you apply the product any lighter.

Now if we use this method to work out the skin surface area of the average person (70Kg, 165cm) we get 1.73 m2.

If we take 75% of that we have 1.3 m2 which is 13000 cm2

If we want to apply 2mg per CM2 we would need 26000mg of product per application.

This is the same as 26g per application.

In this study the product was applied 4 times during the day.  This was following pack instructions.

So each participant wore 104g of sunscreen per day.

**** Before you judge the rest of this study it is worth reflecting on the above.  Have you ever used sunscreen like that? does that amount surprise you? Is it representative of reality that SPF is calculated based on that application?  ****

Next time you go for your weeks holiday remember to take 2 litres of sunscreen per family of 4. 

This protocol looked at the following target actives:





Systemic concentrations greater than 0.5 ng/mL were reached for all 4 products after 4 applications on day 1 (direct quote from here).  0.5ng/ml is equivalent to 0.00000005%

I wanted to be able to visualise or relate to that number better as it seems very small. Maybe worrying is unnecessary after all…

To put the findings into percentage terms, which I relate to better, the ingredient found at the highest concentration after the four days was oxybenzone and it was found at concentrations of 209.6ng/ml which is the same as 0.000021% of the blood.

I’m not a pharmacologist so I may have interpreted this incorrectly but a standard dose of paracetamol gives a blood ‘active’ level of around 30mg/l or 0.003%

Looking at the contraceptive pill which interacts with our hormones we see that a typical regimen results in a blood concentration of 0.0000006%. This is based on the report I found here. 

Now I decided to look into the typical blood concentrations of other chemicals to help me build up a reference framework for how big or small a change in our blood this represented. I claim no equivalence between these drugs but I chose paracetamol because that’s a drug that most people have a relationship with (having taken it before) and the contraceptive pill because again, most people understand that and also because this drug affects our hormones and one common fear about sunscreens, especially the chemical ones, is that they are hormone disruptors.  All I can conclude from my exercise is that the sunscreen actives were present at a level significantly higher than that expected when taking the contraceptive pill.  This doesn’t mean that these chemicals will work like the contraceptive pill.  Each drug has its own pharmacology, but I feel this comparison does add something to the debate. It seems more urgent to me that we address this, at least so we can fully understand it better.

So sunscreen actives get into the blood to some degree. Why?

Another potential failing I see highlighted in this study is that of efficacy.  If a proportion of your sunscreen slips into your blood steam it can’t reduce the burning effect of the suns energy as it is nowhere near the UV at that point.  What I want to know is this.  Is this a failure of the formulator or a failure of the ingredients manufacturers to fully understand the solubility of their actives?

A formulator can only formulate within the scope of their ‘view’ so they review data from manufacturers, create a chassis (or base) which should hold or deliver those actives and then work on the softer features (price, look, feel, smell) to improve consumer appeal. If there was no data available to formulators about potential skin penetration then the only measure the formulator has with regards to efficacy is standard SPF testing and consumer aesthetic trials.  If neither of those required a MUsT study and if the product reached the expected SPF within usage guidelines then there would be no need (or money probably) to investigate further.

So why wasn’t skin penetration of actives tested before?

I don’t know how much data exists but if the FDA are correct, they weren’t presented with enough data outlining how likely these particular actives are to penetrate to ascertain their safety.  It could be that data did exist but wasn’t shared or that data just did not exist. In either case, it’s time for that to change.

What the article and study I’ve linked to above do point out is that test methods and tracking protocols have progressed over the years so it is possible that it has only been recently that the tracking of the chemicals found in sunscreen can be traced in this way.  Further, even if this type of tracking has been available for a long time, unless it is part of an actual SPF approval process (which it is not), there would be no obligation for independent sunscreen manufacturers to carry out this testing.  It is easy, as a consumer to sit there and think ‘well shouldn’t they do everything in their power to prove their products safety’ but let’s face it, we’ve all gone to the supermarket and bought a litre of the cheapest stuff with the highest SPF as we’ve either run out of money or can’t see the point in spending double on the same thing.  Testing is expensive and testing like the FDA just did may make it impossible for smaller, boutique brands to participate so unless the playing field is level. So, in short, this requirement may have to be legislated for in or

Is there anything else worth noting at this point in time?

As far as I am concerned I believe that the FDA have taken a great step towards making sunscreens better and safer for all of us.  Even if it turns out that the levels of sunscreen active absorbed make zero difference to our or our planets health,  as a cosmetic chemist I’d still want to improve products to stop the dermal penetration of actives.  If nothing else, it is a complete waste of resources and energy to have these chemicals end up in the blood. It’s like swallowing a raincoat and expecting it to keep you dry.

The article is right to note that dermal absorption does not automatically mean death (or even slight inconvenience to ones health).  Chemicals can be absorbed and just excreted with minimal fuss, absorbed and cause minor issues, absorbed and improve our life or absorbed and bioaccumulate, causing longer-term problems.  As humans our instinct is to fear the worst but that’s not necessarily helpful.  We know that too much sun will give us skin cancers and for many of us, sunscreen is a necessity if we wish to enjoy the great outdoors.  My advice is to continue to watch this space avidly, to continue with ‘safe sun’ behaviour, however you choose to interpret that, and to encourage your sunscreen providers to be part of this advancement of science.

As an industry I feel we should welcome any scientific investigation into our ingredients and/or products, especially when they are lead by a team like the FDA who has safety as their key objective.  It is all too easy for us to brush off things like this saying ‘just keep slapping on the sunscreen folks, nothing to see here’ but that’s part of the reason why nobody trusts us.

I don’t know how the dice will fall when this study is expanded and/or when all of the sunscreen manufacturers come forth with their data but I do know that necessity is the mother of invention and maybe, now, because of the FDA all of us sunscreen industry participants will NEED to get our thinking caps on as we aim for zero dermal penetration and more reflective (of how products are actually used) SPF testing.

The campaign for Zero penetration….

Doesn’t sound like it will catch on, must think up another slogan 🙂


PS: I’m putting this report by MDPI here as this is also interesting and I want to digest this further.  This report looks at how studies into dermal penetration of sunscreens have been carried out in the past.  This raises a number of interesting questions too, especially in light of the FDA report above.

PPS: I didn’t talk much about the fact that in the FDA study the test subjects were inside and the group was small because I felt that it was clear that this was a first-step study so these conditions could be looked into during further studies. Staying inside is unlikely to make a sunscreen more likely to penetrate in my opinion.

2 Comments leave one →
  1. May 13, 2019 9:04 pm

    Bahhahahaaa! The campaign for zero penetration! As usual, excellent post Amanda.

    • RealizeBeautyEd permalink*
      May 14, 2019 9:46 am

      Lol, apparently laughing is good for the soul and complexion 🙂

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