Chatting (Version 2)

I agree, @Ethelinde, sunscreen testing is not an exact science and the results vary depending on the lab. Michelle @ Labmuffin release a short video in response, she explains the issues and inconsistencies around testing. So I would probably only avoid a product if there have been multiple labs showing that the test significantly lower than the label.

@labmuffinbeautyscience

Did you see the Choice sunscreen testing results? Here’s an SPF deep dive! Key points: • Sunscreens are very effective, these results do not indicate that you should lose faith in them • SPF testing is a lot less precise than it might seem – this is an inherent limitation of the test, there’s a lot of variation with results even if nothing has gone “wrong” • Formulas can change over time (slight changes in raw ingredients etc) • I’d guess a lot of “fails” are explained by interlab variability (the lab Choice used tends to get numbers on the lower end), the rest by formulas changing over time (especially the ones that tested much lower) • Mineral sunscreens are generally less robust, more easily affected by small changes (also seen in Consumer Reports tests) • The newer ISO tests should improve reproducibility, and make it easier for brands to ensure SPF won’t drift over time (maybe this should be required?) • User error is a much bigger cause of sunscreen failure than sunscreen formulas (not applying enough, not reapplying, relying on sunscreen alone) • MEASURE YOUR FINGERS 😤😤😤 • The largest clinical trial on sunscreen (the Nambour trial) found huge benefits from SPF 16 (and it didn’t look very photostable!) Other notes: • I think brands with lower SPF results should investigate – most brand statements indicate they’re doing that, but there are a few bizarre claims in there (IMO)… • SPF 50+ actually means SPF 60 or over in Australia, so technically only 2 sunscreens “passed”, not 4 • I don’t love the framing of one lab’s results as the “true” SPF, but the imprecise nature of SPF testing doesn’t seem well known (also SPF tests have a +/-17% (95% CI) limit, for methodology nerds) • MEASURE YOUR FINGERS 😤😤😤 • I talked about 2010 and 2019 ISO24444 together – 2010 is still allowed for AU sunscreens launched before July 2024 (changes mostly impacted reproducibility) #spf #sunscreen #skincare #instaskincare

♬ original sound – Lab Muffin Beauty Science