We are all familiar with the human-caused emissions of certain refrigerants and propellants (e.g., CFCs), which led to the most severe depletion of the ozone layer in the stratosphere in the year 2000. After a period of recovery, research teams discovered in 2018 that the ozone layer is once again thinning in the lower layers of the stratosphere over mid-latitudes (including Germany). Global warming and short-lived chlorine- and bromine-containing chemicals are now suspected to be possible causes. 

According to the Federal Office for Radiation Protection, this has resulted in an increase in UV radiation intensity of approximately 7 percent in winter and spring and approximately 4 percent in summer and fall. This refers to the increasing intensity of solar radiation (in watts per square meter), which raises the risk of sunburn. In recent decades, we have seen a decrease in cloud cover and an increase in annual hours of sunshine on the Earth’s surface in Germany. In addition, passing air masses with low ozone levels—so-called “low-ozone events”—cause sudden and unexpected spikes in UV radiation intensity.

The low-ozone events that occur in late March and early April are a health concern because, at this time of year, high levels of UV radiation—which are typical in early summer—are not expected, and therefore people do not take the necessary sun protection measures. Unnoticed, the skin and eyes are at risk of UV overexposure, as UV radiation is imperceptible to humans. That is why it is important to check the UV Index (UVI)—an internationally standardized measure of UV radiation capable of causing sunburn—by region and time of day as early as early spring; see the list of links below. The UVI ranges from 1 (low) to 11 (extreme).

UV radiation is the leading cause of skin cancer—the most common cancer among fair-skinned people worldwide—as well as eye cancers and UV-induced lens clouding (cataracts). The more sunburns a person experiences during childhood, the greater the likelihood of developing skin cancer in adulthood. Children’s skin is many times thinner than that of adults and cannot yet produce sufficient pigment to act as the body’s natural protection against UV rays.

According to scientific findings, both UV-B radiation—which causes sunburn—and UV-A radiation are responsible for light-induced skin damage. The harmful effects of UVA radiation are not immediately apparent but manifest as long-term damage: the skin ages more quickly, develops age spots, and, in the worst cases, can even lead to skin cancer. 

It’s important to know that how long you can stay in the sun depends on your skin type. Depending on your skin type, your skin’s natural protection lasts only 5 to a maximum of 30 minutes. When your skin tans, that’s a natural protective mechanism. The sun’s UV radiation penetrates the skin and damages the cells there. To protect itself from further damage, the body produces more of the dark pigment melanin, which absorbs and deflects UV rays but does not protect against sunburn. Depending on sensitivity to UV radiation, there are six distinct skin types. If you know your skin type, you can tailor your sun protection precisely to your skin’s needs. For a skin type test, see the list of links below.

According to the Federal Office for Radiation Protection, the period between 11 a.m. and 3 p.m. is critical in terms of solar radiation. It recommends avoiding the sun during this time. 

The best and simplest protection comes from wearing clothing and a hat. The hat should also protect your ears and the back of your neck and shade your eyes. When it comes to shoes, remember to cover the tops of your feet as well. When swimming, UV radiation is reflected by the water, thereby intensifying its effects. In this case, a T-shirt or special UV-protective swimwear, for example, offers effective protection. Wear sunglasses to prevent eye damage. When checking the filter’s effectiveness, look for the manufacturer’s indication of absolute UV protection (UV 400) and sufficient side protection. If you are taking medication, be aware of possible side effects related to sunlight (phototoxic reactions).

When spending time in the sun, only uncovered skin is protected with sunscreen, which delays the onset of sunburn. The sun protection factor (SPF) describes protection against UV-B radiation. It indicates how much longer you can theoretically stay in the sun with sunscreen without getting sunburned compared to what would be possible without it. Using a simple formula (sun protection factor × skin type = maximum exposure time), you can determine the approximate maximum protected exposure time in the sun, taking into account the natural protection time for your individual skin type.

Did you know? This is how much sunscreen you need: To achieve the SPF listed on the sunscreen, you must apply 2 milligrams (mg) of sunscreen per square centimeter of skin. For an adult, that’s four heaping tablespoons for the entire body. With a 200-milliliter bottle, the bottle will be empty after five applications; if you reapply two to three times a day, the sunscreen will last for two days. 

If too little is applied, or if the sunscreen is reduced by washing or rubbing it off, the SPF is lowered. To maintain the sunscreen’s effectiveness, it is important to reapply it repeatedly. However, this only maintains the effectiveness—it does not extend the duration of protection. It should also be applied 20–30 minutes before going out in the sun. Only then can you be sure that the protection is fully effective.

When purchasing sunscreen, check the following points:

• The product has at least the recommended SPF 30 (high protection). Activities at high altitudes, on snow, near or in water, and in sunny regions require sunscreen with a very high SPF (50+, very high protection). Very high protection is also recommended for children, people sensitive to UV rays, and those with skin types I and II.
• Protection against UVA radiation is clearly indicated on the product.
• The ingredients are listed to account for possible sensitivities.
• The product typically has a shelf life of twelve months after opening when stored in a cool, dark place. In general, however, you should no longer use opened bottles from the previous year.

By the way, sunscreen, sun lotion (also called sun milk), and sun gel are equally effective. Their differences lie in their composition, or rather, in the way the various ingredients have been dissolved. The product name “sunblock,” which was used in the past, is no longer used because consumers might mistakenly assume it provides complete protection.