Safer Sun (III)

Safer Sun (III)

Part III: A lot helps a lot?

The right amount of sunscreen


by Dr. Huong Nguyen | Editor: Dr. Sabine Nunius | June 30, 2022

A lot helps a lot!??

You know which SPF you need - so using it is now self-explanatory!? Not quite, because there is still a small plot twist.

To achieve the SPF declared on the packaging, an application quantity of 2 mg/cm2 is required. So you have to cream very generously!

As an illustration:
• You need about two finger lengths (= length of the index and middle fingers) of cream for your face and décolleté alone. They are actually finger LENGTHS, not widths.
• Based on the entire body of an adult, around 30 to 40 ml must be calculated, i.e. around a fifth of a 200 ml bottle! Approximately 20 ml of sunscreen is recommended for a child aged ten.

If you now think about the last time you used so much cream - you are not alone!

FACT of the day

To achieve the SPF declared on the packaging, you would need an application amount of 2 mg/cm2!

Sun protection effectiveness is overestimated in practice!

Experts estimate that in practice only a third of the specified sun protection factor is actually achieved. The protective effect is usually OVERestimated. Because if you apply a sunscreen with SPF 50 but only half the required amount, you don't have SPF 25 - as you might imagine. Because the protective effect does not fall off linearly, but exponentially: the square root of 50 results in an SPF of 7. And unfortunately that is actually not enough!

However, this is not primarily due to us, but rather due to the fact that we have to apply an unphysiologically high layer of product in order to achieve the specified SPF. I also often find it difficult to adhere to the quantities given, especially when I apply the almost obligatory sunscreen every day after facial care.

What to do?

So how do we get out of this dilemma? We can simply get into the habit of shortening our time in the sun and not fully utilizing the calculated, individual protection time! As a rule of thumb, some official sources even recommend only using up to about a quarter of the maximum exposure time. In this way we avoid the development of sunburn and also minimize the risk of light-related long-term consequences.

Why can't we extend the length of stay despite applying cream?

Despite sunscreen, a certain dose of radiation reaches the skin per unit of time. This adds up over the course of the day until the skin's tolerance limit is reached. This time can only be used once per day, otherwise the skin's repair mechanisms will be overloaded. Even repeated applications do not extend this time. However, by regularly reapplying the cream, we ensure that the light protection film on the skin, which gets 'holes' through sweating, bathing or abrasion (when drying off), is 'refilled'.

When to apply cream?

It is often said that sun protection products should be applied 20 to 30 minutes before sunbathing. This rule is a thing of the past. For both sun protection products with chemical UV filters and sun creams with mineral filters (e.g. titanium oxide or zinc oxide), it is sufficient if they are applied to the skin shortly before first contact with the sun. However, it always takes a while in the sun before we have completely applied the cream. Therefore, it is actually advisable to start sunbathing 'prepared' and wearing full sun protection gear.

What's next?

We have almost reached the end of our Safer Sun series. Finally, we will cover two more topics in this series:

• Which UV filters should I use?

• How can I strengthen my UV defense through diet?

We look forward to having you read it again!

Until then, happy and safe sunscreening!