Consumer NZ has done its annual “testing” of sunscreens and has hit the media claiming many sunscreens don’t measure up to their packaging claims. It’s nonsense.

I’ve put “testing” in inverted commas because if the methodology used is the same as in previous years, though it’s “sciencey” in impression, it’s neither science nor a fair or genuine test of the sunscreens’ efficacy.

I know that the science behind testing SPF has been explained to Consumer NZ at length over the years, but this doesn’t seem to have changed some of the misleading and scaremongering comments made about sunscreens, which achieve little more than undermining their use in New Zealand by confusing consumers and undermining their faith in products.

There is no doubt NZ Food & Grocery Council member products, such as Banana Boat and Hawaiian Tropic, meet New Zealand law – the Cosmetic Products Group Standard and the Fair Trading Act – so when Consumer NZ says companies “can say what they want” in this market, that’s simply not true.

These sunscreens also meet Australia’s Therapeutic Goods Act (TGA) regulations, which means they meet the same (high) standards as medicines. These are the standards Consumer NZ is advocating that sunscreens sold in New Zealand follow. You would think, therefore, their article should reference those standards and regulations, but it does not do that with any degree of balance. I understand that the Cancer Society and SunSense brands also meet TGA standards.

So why does Consumer NZ get such results? A few reasons: variation across a lab’s interpretation and application of the test methodology, the observational nature of the test, environmental conditions the bottle is kept in, and age of the product.

I understand that some of the products tested were nearly three years old and very close to their expiry date. When companies test their products, they do so at scale and at the factory.  They test formulations and hold batch samples for future reference.

Consumer NZ has made a big deal over the fact that some of the test results provided by companies are not recent. This shows how little Consumer NZ understands about how therapeutic goods are tested and manufactured.

The age of the test is irrelevant because testing is done at the start of the first batch produced, and then repeated ongoing, including quality tested with batch testing, replicating the formulation, as is common practice across medicines. This is highly audited, and compliance is guaranteed, given the robust nature of the process.

Casting doubt on rigorous scientific testing by questioning when the test was done is dangerous because it spreads uneducated and misleading information about the science involved. This lack of critical investigation and presentation of scientific facts is alarming and falls into the category of fake news and tabloid journalism.

There are so many scientific reasons why post-production testing is not a reliable way to test sunscreens. (It’s also why blood pressure medicine is not tested in this way).

SPF testing can vary. The tests involve applying sunscreen to a person, irradiating the skin, waiting, then observing and noting the level of change to the skin. This is where variability can happen between labs when technicians make different judgments by sight about what is pink to red.

Therefore, it is not surprising that different labs sometimes produce different SPF results for the same product batch. Variability within the same lab is more concerning. A company told me at a recent sunscreen industry meeting that they had sent three samples of the same batch of sunscreen to the lab used by Consumer NZ and got three different results.

In summary, it’s an observational science, even under strict and controlled processes.

Due to the variability in SPF testing of sunscreen, the International Organisation for Standarisation (ISO) committee has undertaken a review of the test and is about to issue an updated standard. This will mean that all global testing labs will have to adhere to a stricter guideline, which will lead to less variability in SPF results. The expectation is that the revisions to the test methodology will be published by the end of this calendar year.

The ISO changes are important because they are a response to inconsistencies in test labs’ processes, not sunscreen manufacturers’ products. These changes will serve to lift the confidence of results coming from all test laboratories.

Consumer NZ would be better to use its main message to remind people about the importance of wearing sunscreen, how much to use, and how often to reapply the creams.

Repeating Slip, Slop, Slap and Wrap should be the main message rather than repeating pseudoscience that misleads people about the efficacy of sunscreens.