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Sun protection
The thing about reapplying sunscreen
Reapplying sunscreen is important for your sun protection. Fact. Reapplying sunscreen maintains sun protection. Fact. However, it is a myth and wrong that it allows you to stay in the sun for an unlimited length of time.
Honestly, it is not that easy to write about the length of time spent in the sun and reapplying sunscreen. With regard to the length of time spent in the sun, there is a practical and a theoretical perspective. In other words, there is the “play it safe” view and the “maximum possible” view. However, variables play a role in both viewpoints. Not straightforward, right?
But we want to address the topics surrounding our beloved sun and the all-important sun protection in a clear and, above all, easy-to-understand way for everyone. For that reason, the topic of reapplying sunscreen is important and necessary. It’s very simple.
Generally, when it comes to sun protection: more is better. It is a good idea to apply sunscreen regularly and it is important not to be too stingy when applying it. It is better to use too much sunscreen than too little. Most people apply too little sunscreen to their skin. If you use a sunscreen with SPF 50 but only apply half the amount you need, you won't be protected as you thought. This is because the actual sun protection factor is usually lower than the value shown on the packaging. And bear in mind all unprotected areas of the body.
Do you know what a golf ball has to do with sun protection? No? Then take a look at this little clip of our expert Myriam.
Difference between theory and practice
Since 1975, the different skin types have been categorized on a scale that is still used today. Knowing your skin type can help you to better plan the necessary protective measures. Here is a little example that only relates to the theory: Assume you have skin type 2. After approximately 10 minutes, you see the first signs of redness, and you are using sunscreen with an SPF of 20. That makes 10 minutes x 20 SPF = 200 minutes in the sun. Please note that this value corresponds to laboratory conditions. The spectrum in the laboratory varies from the natural solar spectrum. The SPF measured in the lab is higher than the SPF outside in the real sun.
This 200 minute value is therefore the absolute “maximum possible”, which should be considered purely theoretical. Because here we come to the variables just mentioned, which can quickly shorten the time span:
- Not enough sunscreen is used
- Sunscreen is applied unevenly over the body
- Mechanical removal, e.g., by clothing or drying with a towel
- Swimming + sweating
- The SPF is measured in the laboratory. The light spectrum varies from the natural solar spectrum.
Psychology also plays a role. When you use a sunscreen with a high level of protection, it is easy to believe that you can enjoy the sun with almost no limits or you can even get a little slack with applying the sunscreen. This is a misconception.
Therefore, do not push the calculated time period to its limits. It is better to only spend 50 percent of that time in the sun. Then you will be of the “play it safe” view. In any case, you should reapply every 60 to 120 minutes within this calculated time period. This allows you to maintain the protective film on the skin evenly and thus maintain the protection.
This is where there is a misunderstanding among many consumers. Please do not confuse maintaining protection with restoring protection. Reapplying sunscreen does not mean that you reset your time account to zero and have the entire duration again. That sounds strange and maybe even illogical without a closer look.
To illustrate this point: Using sunscreen does not mean that your skin is 100% protected from UV rays. With SPF 30, for example, approximately 3.3% of UV light ends up on and under the skin and causes damage there. This is associated with chemical reactions and biological processes that are fundamental to our lives, but also involve dangers.
Skin remembers years later
While exposed to the sun, the body collects UV rays and thereby fills up its so-called UV account. The amount of “captured” radiation and its effect on skin and eyes accumulates over the course of the day. When the account is full, the first visible signs of skin change will appear, and this is followed by the first visible change, sunburn. Tanned skin is also a reflection of the damage that has occurred and is therefore a false and dangerous beauty ideal.
The light protection or sun protection factor
Describes the skin’s protection against sunburn, the technical term for which is erythema. This redness of the skin, the first visible sign of skin damage, is caused by UV light within a wave range of 290–400 nm.
SPF classifications
SPF 6–10 – Low protection
SPF 15–20 – Medium protection
SPF 30–50 – High protection
SPF 50+ - Very high protection
However, the skin is already affected before sunburn sets in. The damage may not be immediately visible, but it triggers processes that inevitably lead to damage later on. Our skin absorbs all this damage and “remembers” it. Years later, effects such as skin aging and skin cancer can become acute.
If your skin has been exposed to too much UV radiation throughout the day, you can't reverse this by applying just as much sunscreen. The best things to do is get out of the sun and replenish. If this is not possible, you should still continue to apply sunscreen with a high SPF to avoid even more damage.
Extending is relative
But let’s take another look at the need to reapply sunscreen. We have our own protection time and a sun protection factor, e.g., 15. This gives us our maximum time in the sun. After half of this time has passed, some of the UV radiation has already penetrated the skin. However, it is not yet enough to cause sunburn. Even so, it is no longer possible for us to double the protection by reapplying sunscreen. However, reapplying is important simply because sunscreen is lost due to perspiration or water, for example.
If we theorize, and the variables did not exist, then reapplying the same SPF 15 would mean that your sun protection would double to 30 after half the time. As a result, you would reach your sunburn threshold, your limit of exposure to the sun, even later.
However, reapplying sunscreen may theoretically extend the sun exposure time, but it will never be doubled or even extended for as long as you wish. And in practice, it will definitely not be possible to determine a precise time. Indeed, we do not live under laboratory conditions. Consider the variables.
We therefore recommend that you always choose the “play it safe” option. Your skin and health will thank you. That is for sure. Easy, right?
The meaning of the different UV index values and the protective measures recommended by the WHO:
1 + 2: No protective measures are required. You can and may enjoy being outdoors without any concerns.
3 to 7: Sun protection required. Prevent damage to health by wearing clothing, a hat and sunglasses. Use sunscreen with a sufficient SPF. Avoid the sun in the middle of the day. Stay indoors or seek shade.
8 and above: Protection is an absolute MUST. You should wear clothing, a hat and sunglasses for the whole day. Avoid being in the sun in the middle of the day. If you are outside, stay in the shade.