The first strong rays of sunshine after the dark winter months lure many people outside, and as they sun themselves, the light prompts their bodies to produce feel-good hormones and vitamin D to stimulate their nervous system.
But the sun's rays are also dangerous as is evidenced by sunburn. The UV rays destroy or alter cell nuclei. The skin can compensate only for part of the damage before it turns red, even when it has its own level of protection.
This level of protection varies depending on skin type and the intensity of the sunlight. It's about 20 minutes for skin that has little or no natural brown. Therefore, the skin needs extra protection. A good way to protect the skin from the UV rays that can cause a burn is to avoid intense sunlight, says Swen Malte John, professor of dermatology at the Osnabrck university.
The most intense sunlight occurs at midday in the height of summer. But the sun can be strong enough at other times of day to seriously damage the skin.
It is nearly impossible to completely protect the body from sunlight, especially during a summer vacation.
"Clothing should cover as much skin as possible," says Heidrun Holstein, a medical specialist at Germany's consumer center in Karlsruhe. She recommends wide-brimmed hats and long-sleeved shirts made of light material and UV-proof material that lets in only a fraction of sunlight.
Those parts of the skin which are not covered by clothing, such as the face and hands, should be protected with sunblock. The most important criteria when selecting a sunblock is skin type. People with darker complexions have a higher level of protection in their skin and can thus select a lower protection factor, says Holstein.
Generally, the sun protection factor (SPF) should be 15 or higher. When going to the beach or into a snowy setting, where the sunlight is reflected, a higher SPF is recommended. It also helps to check the UV index, which places a numerical value on the expected peak sunburn-causing UV rays. In some countries it's possible to find the forecast UV index on the Internet, and sometimes the index is given as part of the weather report.
A sunblock's description should also contain a few key words and should indicate that the product protects not only against UV-B rays, but also UV-A. It also should provide some information about whether the product is water resistant.
There also are major differences in the ingredients of sunblocks. Dermatologists recommend so-called physical protection. Such products contain crystals made of micro-sized minerals that reflect UV rays, says John. The more chemical substances contained in the product, the greater the risk of an allergic reaction.
After exposure to sunlight the skin needs calm and care.
"A cool bath or a cold shower is especially good," says Grohn. "Then use a moisturizing lotion or gel with a high amount of aloe vera."