At the onset of every summer, many organizations publish their newest lists of the best sunscreens for that season. These lists tend not to agree with one another, and so the associated debates and disagreements continue, one season after another.
The root cause of this situation appears to be the less-than-clear definition of sunscreen performance, as well as its related testing methods.
Accordingly, let us attempt to explain this situation in layman’s terms and in the hopes of advancing better ideas from dedicated professionals in this field.
Let’s start by randomly quoting one of the latest best sunscreen lists: In CNN’s “The best sunscreens in 2023 tested by editors”, it is stated, “we didn’t test how well these sunscreens protect skin from the sun — for that, we relied on information from the US Food and Drug Administration and the experts we talked to.
Too many variables (skin type, time of day, the sun’s intensity, etc.) made it impossible to accurately measure efficacy in our real-world testing.
Rather, we had multiple testers with different skin types and tones test them for other variables such as feel, appearance on the skin, smell, ease of application and more.”
In other words, the performance and effectiveness of sunscreen, which are the primary reasons for using the product, have become so confusing that most people avoid the topic altogether.
Instead, they focus only on the sensory factors. Of course, sunscreens should be pleasant to wear so that people are willing to apply them. However, sensory factors should not replace effectiveness in the judgments of product quality.
We will focus on the performance aspect of sunscreen in our discussion here.
The metric most often used when describing sunscreen performance is SPF, the Sunscreen Performance Factor, which is a measurement of how long it takes for UV rays to hit and damage your skin. For example, SPF 30 means that when you wear this sunscreen, it will take you 30 times longer to burn compared to when you are not wearing any sunscreen at all.
Essentially, the sunscreen industry has adopted a performance metric that measures the UV ray dosage that reaches skin with sunscreen applied relative to the dosage that reaches skin without sunscreen.
Consequently, there are many variables that impact the measurable performance and apparent effectiveness of sunscreen. Skin type and irradiation source are commonly mentioned, as in the CNN article from earlier.
These two factors are important, but they are relatively easy to control. The skin type of a particular consumer is fixed, and when comparing the skin’s reaction to irradiation with and without sunscreen, the same sunlight source is normally used.
The largest variable influencing sunscreen’s effectiveness on a consumer’s skin is the amount of sunscreen applied and the quality of that application.
Due to the nature of UV prevention ingredients, consumers cannot see with the naked eye the sunscreen that they have applied to their skin.
Therefore, they cannot easily judge if they have applied enough sunscreen or applied it evenly. However, the amount and uniformity of sunscreen on skin are the primary factors that determine the effectiveness of a particular sunscreen application.
Consumers are often told to use one ounce of sunscreen on their entire body; in other words, approximately enough sunscreen to fill a shot glass. This is obviously vague and not at all quantitative.
As for the quality of sunscreen application, which determines the uniformity of coverage on skin, this is even more difficult to perceive and is rarely conveyed to consumers.
The performances of sunscreens are professionally tested before the sunscreens are put on the market. There are several standard testing methods instituted by governmental and industrial regulatory organizations, but they are essentially the same in that they all measure the relative UV ray dosage that reaches the skin with and without sunscreen applied.
In these testing methods, the type of skin (substrate), the type of light source (irradiation), the amount of sunscreen (weight per area), and the end point (skin reddening or darkening) are carefully specified.
However, the quality of application (uniformity of coverage) is not carefully controlled or monitored. The end point determination is often a visual determination and is therefore not very quantitative.
These factors, coupled with the fact that tests are often measuring the last few percentages of the total irradiation reaching skin, make accurate sunscreen performance testing a well-known challenge.
For example, to tell the difference between SPF 50 (100/2) and SPF 100 (100/1) is to measure the difference between 2% and 1% of the original UV irradiation; consequently, small variations in measurements can lead to large differences in the calculated SPF.
As such, there have been many reported conflicts regarding the reliability of sunscreen efficacy tests.
In addition, it is logically challenging to test and label the performance of a sunscreen product when the product’s true performance is only on display after it is properly applied to a skin. It’s like trying to test a tube of oil paint to determine its degree of virtuosity, even though it can only attain virtuosity after being applied to canvas by a virtuoso.
The intended objective of applying sunscreen is to prevent harmful sun rays from reaching the consumer’s skin. Therefore, the only true test of a sunscreen’s effectiveness needs to be performed in real time, on the skin, and in a real-life scenario.
While an easy and convenient way to measure the real-life performance of sunscreen is not yet widely available, we hope that the obvious need for such a technology will soon motivate its invention.
Once a relevant performance metric becomes available to everyday consumers, they will be able to easily pick the best performing products. When that happens, the sunscreen industry will be fundamentally changed.
As we have detailed in past articles, sunscreen technologies that allow for pleasant and uniform coverage on skin are essential to the creation of sunscreen products that perform well in real life.
These products will enable every consumer to easily master the art of sunscreen application, thereby becoming the obvious number one pick of every best sunscreen list.
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