Sunscreen SPF numbers have long been linked to measuring the extent of erythema after exposing human skin to ultraviolet radiation. Recently, however, the European Union released the results of a joint test showing that protection can also be assessed reliably through laboratory testing that does not deliberately expose people to sunburn. Cosmetic testing may seem remote from consumers, but this represents a change in how the SPF numbers we see every day are produced. [1]
What did the EU test?
According to the European Commission, market surveillance authorities in 11 EU countries selected 74 sunscreens and day creams from stores and online retailers, then measured their SPF and UVA protection under laboratory conditions. The Commission said that a high correlation was found between in vitro and existing in vivo methods. [1]
What is different about in vitro SPF testing?
In vitro testing evaluates a product’s UV protection under laboratory conditions rather than on the human body. Conventional human testing may involve observing the skin’s response after exposure to ultraviolet radiation. If laboratory testing is sufficiently reliable, its key significance is that it could reduce the burden of deliberately inducing erythema in people. [1]
So can we take sunscreen SPF numbers at face value?
The stated SPF is a value obtained under specified test conditions, not a guarantee that you will never burn for a certain number of hours in real life. Actual protection is affected by the amount applied, whether it is spread evenly, sweat and water, friction, and reapplication. The Commission likewise advises choosing products with SPF and UVA protection suited to your skin type and level of exposure, applying them generously and evenly, and reapplying. [1]
Why should SPF and UVA be considered separately?
SPF is primarily an indicator related to protection against erythema caused by UVB. But when everyday photoaging and pigmentation concerns are considered, UVA protection should also be checked. When choosing a product, it is therefore more reasonable to consider the UVA protection label and the conditions of use together, rather than focusing only on the SPF number.
Is homemade sunscreen acceptable if it contains good ingredients?
No. A sunscreen’s actual SPF and UVA protection cannot be predicted from its ingredient list alone. The European Commission also warns that UV filters require assessment and authorization, and that homemade sunscreen can pose a health risk because its protective performance has not been verified. [1][2]
Does SPF 50 last twice as long as SPF 30?
It should not be calculated that simply. SPF is not a timer that directly indicates how long you can stay outdoors. Applying enough product and reapplying are more important.
Is sunscreen necessary on cloudy days?
If you will be exposed to UV outdoors, it is better to consider the duration of exposure and your activities rather than deciding whether to skip sunscreen based on the weather alone. For extended outdoor activities, consider both UVA and UVB protection.
DERME VERDICT
What is interesting about this EU test is not that it found a ‘higher SPF,’ but that it demonstrated the possibility of validating the number through a more ethical and reproducible method. The principle for consumers is simple: look beyond the competition over SPF numbers and consider UVA protection, applying a sufficient amount, and reapplying as part of real-world use.
