How to best tell if your zinc sunscreen is safe.

Response to “Natural” Sunscreen Controversy

How to best tell if your zinc sunscreen is safe.

How to best tell if your zinc sunscreen is safe.

The internet has been on fire, again, this summer with the recent controversy over The Honest Company TM’s specific ‘natural’ zinc oxide sunscreen.  Out of respect for them as a competitor, we won’t speak to their specific case but we felt it was important to address the issue as it balloons out to others relating to sunscreens.  We’ve been hearing a lot of “are ‘natural’ sunscreens safe?” and general questioning of zinc oxide based sunscreens.  If you read our blog consistently then this might contain some repetition but we felt we had to put our view point out there and address some of the inaccuracies that are flying about.

Issue #1: What does Natural Mean?

This has always been a thorny issue- we don’t actually claim all-natural on our products or really emphasize this in our marketing.  Zinc oxide is a chemical- it’s true.  The zinc oxide found in sunscreens has been processed considerably for very important formulation based reasons.  Particle size, distribution, and the material it’s dispersed in are addressed in a lab and not in nature.  However, their safety stems from the fact that they are considered large particle based filters that sit on the surface of the skin.  Even nano forms of skin are too large to be absorbed by healthy, intact skin and studies have repeatedly confirmed that even on damaged or broken skin, they remain within the upper dead layers.

Zinc oxide is sometimes referred to as a physical filter but even this is not completely accurate.  Micronized and nano sized zinc actually reflect light (i.e provide physical protection) and absorb and scatter UV light (provide a chemical type of protection).  Truly accurate terms would be inorganic (from your days of highschool chemistry not related to environmental claims like in organic agriculture) or particulate based filters.

Issue #2: Is Zinc Safe? Is it Effective?

Zinc’s safety comes from the fact that it’s still the only filter in North America that can provide the most complete broad-spectrum protection against both the UVB (burning rays) and UVA (aging rays, both UVB and UVA cause cancer).  There are other filters world-wide which provide broad-spectrum protection (hello Tinosorbs!) but they are not approved for mainstream use in the US and Canada.

Until then, zinc is the only filter that can provide complete protection but only if used in a high concentration. The maximum allowable in North America is 25%-  and there is a big difference between a formula that has 22% vs. 9%.  The more zinc the better protection.

Issue # 3: What Other Factors can Affect Protection?

Formulating a good sunscreen is actually quite technical and is complicated.  Factors like pH can affect whether the zinc is in its active form- a formula with too low pH can actually render the zinc oxide inert.  Dispersion plays a role.  Zinc oxide can absolutely be dispersed so that it’s evenly and uniformly distributed within a formula.  There are some brands that require customers to shake or knead a product- these formulas will show separation otherwise.  You know your formula has separated when clear oils burst from the tub or packaging and the white zinc comes out separately.  In our minds, that shows product instability and is not a good thing.  Our formulas stay emulsified over the course of their shelf life, which ensures that you are getting uniform amounts of zinc oxide with every application.

Issue #4: How are Zinc Oxide sunscreens tested?  

In Canada, zinc oxide and titanium dioxide sunscreens are regulated by the Health Canada division of the Natural Health Products Division.  They are regulated differently than the sunscreens that include the other filters but these regulations deal more with manufacturing practices.  The Good Manufacturing Practices for Natural Health Products are quite sensible and in fact Health Canada has stated that the practices for the other type of sunscreens might be too excessive and actually blocking innovation in the industry (which impacts Canadians ability to access the best and latest in sunscreen innovation).  In Canada, a sunscreen with a Natural Health Number must with every batch produced show that they contain the amount of active ingredient as per their label and that they are free from bacterial growth.

Issue #5: How is their SPF tested?

In terms of SPF, before a sunscreen is approved (i.e. before it gets to production phase), a company has to submit results from the FDA standardized method of SPF testing.  This is true of all sunscreens that are approved for sale in Canada, irregardless of the active ingredient found within them.  SPF tests are done on human volunteers since there is no currently accepted standard for measuring SPF in-vitro ( a lab, normally using acrylic plates, not people and not animals).  Hopefully, this will change one day, as you could argue there are ethical issues with irradiating humans.

However, while this SPF test is required and standardized, that does not mean that it’s a perfect test by any means.  We’ve repeatedly argued that many labels simply do not make sense in terms of their reported SPF’s.  There is a SPF type of arithmetic that is widely accepted in the industry.  If the SPF is seemingly too high for the amount of active that is within the product then you can know for sure that some formulatory chicanery has taken place.  These SPF manipulations are allowed within the standard protocol of testing (i.e. the company is not lying about their results)- it’s just that these results are the product of gaming the test.

Briefly, SPF tests rely on the measurement of redness produced within the skin.  When compared to a standardized formula, a sunscreen with a low SPF will still allow for redness to be created in the human volunteers skin after being irradiated with UV light.  A higher SPF in theory would prevent more redness from appearing.  Unfortunately, you can alter this response by including anti-inflammatories and anti-oxidants.  For example, aspirin reduces our body’s natural response to become red when exposed to UV light, which is why you take it if you have a sunburn.  However, it does not prevent or repair damage done.  It just takes away the biological marker that tells us that damage has been done.  There are plenty of anti-inflammatories that can be considered natural- for example the derivative of chamomile.  Anti-oxidants do provide some repair in addition to redness reduction but they don’t prevent damage like a typical sunscreen filter.

If you are worried that your SPF might be artificially inflated, you can use the chart below to do your basic SPF calculation.  A very well-formulated sunscreen will provide protection towards the higher ranges but there is very little to no chance that an active would produce any more.  In short, if your sunscreen has 10% or less zinc oxide and no other active ingredients listed, it’s unlikely to be a true SPF 30 and most likely used anti-inflammatories and anti-oxidants in their non-active ingredients to artificially boost the SPF during testing.

The chart below shows the theoretical maximum # of SPF units that 1% of any active could possible deliver.  These are theoretical maximums and real life figures could be lower.  As an example, a sunscreen that has only 10% zinc oxide can in theory have a maximum true SPF of 16 (10 x 1.6).  However, if you were to add 7.5% of titanium dioxide (a filter that protects mostly against UVB and a little UVA), your new true SPF could in theory be an SPF 35.5 ((10 x 1.6)+ (7.5 x 2.6)).

Filter Max. # of SPF Units per 1% of Active
Octinoxate 2.8
Homosalate 1.5
Titanium Dioxide 2.6
Octisalate 1.6
Oxybenzone 2.3
Octocrylene 2.1
Avobenzone 1.9
Zinc Oxide 1.6
Tinosorb M 2.2
Tinosorb S 3.1

Hopefully, this will begin to provide some explanation for some of the controversy going around right now.  We haven’t even touched on UVA protection, safety of ingredients from an endocrine disruption point of view, issues with regulation or third-party seals like the CDA logo.  We regularly post about sunscreens though so if you are interested, I’d recommend staying tuned each month.  Until then, let us know what you think and feel free to write in with questions.

All the best,