Why does sunlight damage the skin and eyes?
The sun warms you, gives you energy, puts you in a good mood and helps you stay healthy. In the long, dark winter months, many people miss it so much. Those who can fly south. All other sun worshippers have to wait until summer. But then they can soak up plenty of sun - but please wear sunscreen and sunglasses. But why do you actually need to protect yourself from sunlight? We explain what UV radiation is - and what makes it as useful as it is dangerous.
Why sun protection is important
As much as the sun lures us outside in the summer, it should now be common knowledge that too much sun, enjoyed unprotected, can cause serious damage. So first the warning: too much direct sunlight is harmful to the skin and eyes. Sunburn in particular should be avoided, as this significantly increases the risk of developing skin cancer as a long-term consequence. What appears as sunburn on the skin can lead to conjunctivitis in the eyes. Direct sunlight promotes clouding of the lens and can, in the worst case, lead to cataracts. UV radiation is said to be responsible for this. UV-B radiation in particular is also considered to be a cause of age-related macular degeneration. In summer, it is therefore not only sensible to think about skin protection, but wearing sunglasses is also recommended. This is even more true for people who spend an above-average amount of time outdoors or are exposed to reflected solar radiation, for example on the beach, on the water, in the snow or in the mountains. However, one might assume that the eye has adapted to sunlight over the course of thousands of years. After all, humans have always spent most of their lives outdoors. But first things first. What exactly is UV radiation and why is it so harmful?
Where is light in the wave spectrum?
What is UV radiation?
The part of solar radiation known as UV radiation is responsible for damage to skin and eyes caused by the sun. Solar radiation consists of a broad spectrum of electromagnetic radiation with different wavelengths. This ranges from radio waves with a wavelength of several kilometers to high-frequency X-rays with a length of just 0.1 nanometers (nm). In between lies what we call sunlight. This is electromagnetic radiation with a wavelength of 380 nm, violet light, to 750 nm, red light, which is visible to the human eye. Between violet and red are the areas for blue, green, yellow and orange. If all areas hit the eye together, white light appears. UV radiation is the abbreviation for ultraviolet radiation, i.e. radiation beyond, Latin ultra, of violet. It extends over a wavelength range from 100 nm to 380 nm. It is therefore no longer visible to the human eye. There are three types of UV radiation: UV-A, UV-B and UV-C radiation. UV-A radiation covers the wave range of 315-380 nm and therefore has the longest wavelength of UV rays and therefore the least energy. UV-B radiation is in the range of 280 - 315 nm and UV-C radiation, i.e. the radiation with the most energy, covers the wave range of 100 - 280 nm.
How are free radicals formed?
Why the shorter wavelengths contain more energy can easily be explained with an image from your vacation. Imagine you are lying on an air mattress on the sea and are rocked by the waves. The waves rise and fall comfortably at a constant distance of five meters. Pleasant, isn't it? Suddenly the same waves come, but at a higher frequency, only 30 cm apart. The comfort is over, you get shaken up and probably even end up in the water. Electromagnetic waves are similar, except that it is our atoms and molecules that are shaken up. The energy of UV radiation is so strong that individual electrons can be knocked out of atoms. This creates ions, i.e. particles that have an electrical charge. UV rays are therefore also known as ionizing radiation. Ions, on the other hand, are extremely reactive and try to form bonds with other atoms or molecules because they want to get rid of their charge as quickly as possible. When ions are created in the human body in this way, they are also referred to as free radicals, as they can trigger undesirable reactions. And that is why we must protect ourselves from UV radiation.
UV protection through the Earth's atmosphere.
Natural protection against UV radiation
The earth's atmosphere forms the first protective shield. The particularly high-energy UV-C radiation is completely absorbed by the atmosphere. The reason for this lies in the wavelength, because the higher the frequency, the greater the probability of the wave hitting a particle and being reflected or absorbed. Most of the UV-B radiation also remains in the atmosphere in this way. Only about ten percent reach the earth's surface. Only the long-wave UV-A radiation reaches the earth's surface almost completely. The skin forms our second protective shield against UV radiation. The long-wave UV-A rays penetrate into the second layer of skin, the dermis. They can damage the connective tissue there and cause the skin to age more quickly. The skin loses its elasticity, becomes flabby and wrinkled. The formation of free radicals also increases the risk of developing skin cancer. However, UV-A radiation also causes a short-term tanning of the skin by changing the melanin pigments. These pigments in turn protect the skin from further UV radiation. The shorter-wave UV-B rays do not penetrate as deeply into the skin. Because they are more energetic, they nevertheless cause greater damage to the skin. They cause sunburn and increase the risk of cancer. The skin reacts to increased UV-B radiation by producing melanin pigments: it turns brown. Melanin pigments can convert UV radiation into heat without forming free radicals. What was long understood in the western world as an expression of beauty and a healthy lifestyle is merely a panic reaction of the skin.
Sunlight is necessary for the formation of vitamin D3
In addition to this ideal of beauty, which is probably far from obsolete, UV-B rays have an actual benefit - because there is nothing bad that is not also good for something. Even if the skin is damaged by excessive exposure to UV rays, which is 10 to 90 minutes depending on the skin type, an occasional sunbath is still necessary. This is the only way the skin can produce the vital vitamin D3. Ten minutes of sunlight a day is recommended in order to produce sufficient amounts of vitamin D3 through the skin.
AMD and cataracts as a result of excessive solar radiation
While the skin can be protected from too much sun with thick clothing or sunscreen, sunglasses are needed for the eyes. The eyes are also at risk of damage from excessive exposure to UV rays. Sunburn of the eye is typically caused by conjunctivitis. While this heals quickly, the long-term consequences can be more serious. UV radiation is considered a possible cause of the development of cataracts, as UV radiation can change the otherwise transparent proteins of the lens so that they become cloudy.
Our body can protect itself – but not sufficiently
The human organism has also adapted to the effects of solar radiation over time. In fact, a healthy life would not be possible without the sun. However, diseases such as AMD and skin cancer are also a consequence of increasing life expectancy. The human body has not yet had time to adapt to the extended lifespan. Therefore, it is all the more important to protect the body and support it for a healthy life in old age.
