Skin and skin types

Our bodies and the sun: reactions can vary wildly

We love the sun and never tire of saying so. As well as being responsible for life on Earth, it does also sometimes cause trouble and health problems. This is where our other favourite topic comes in: sun protection. The relationship between our bodies and the sun causes a wide variety of different reactions.

It is incandescent with fatal rays and swallows up everything that enters the field of its gravitational force. Hellish temperatures prevail on and inside the sun. Inside it is 15 million degrees Celsius. The surface temperature, by contrast, is just under 6,000°C. Even so, its light is regarded as the source of life on Earth. We owe our daylight to the fact that every square meter of the sun emits more light than a million light bulbs and that the sunlight that reaches Earth is diffused by our planet's atmosphere. Without sunlight, the earth would be pitch dark– in the truest sense of the word. There would be no plants, animals or humans, nor any other form of life. 

"UV radiation not only damages your DNA, which increases the risk of developing skin cancer – it also significantly weakens the connective tissue in your skin, making it one of the prime factors behind premature skin aging," says Dr. Christian Cremer, Director of Global Development & Technical Service UV Protection at BASF in Grenzach.

Positive effects of sunlight

  • The sun’s rays stimulate the formation of nitric oxide in the skin, which in turn encourages the expansion of our blood vessels. This reduces arterial pressure and lowers our blood pressure, which in turn diminishes the risk of heart attacks and strokes over the long term 
  • Sunlight stimulates breathing, blood circulation and our metabolism 
  • Production of vitamin D 
  • Thickening of the upper layer of the skin 
  • When there is enough sunlight, the body releases more of the happy hormone serotonin, putting people in a better mood and making them calmer, more satisfied and happier 
  • Sunlight inhibits the creation of the sleep hormone melatonin, which makes us feel tired

Damage that is not directly visible can also be caused, e.g. 

  • Direct and indirect damage to DNA 
  • Damage to collagen and elastin 
  • Formation of free radicals 
  • Immunosuppression 
  • Inflammation of the conjunctiva and cornea in the eyes

Visible signs of excess exposure to the sun 

  • Sunburn (mainly UVB, partly UVA) 
  • Premature skin aging / wrinkles / leathery skin / moles or liver spots 
  • Skin cancers (basal and squamous cell carcinoma, melanoma) 
  • Cataracts 
  • Heat damage, e.g. sunstroke 
  • Increased melanin production for the skin’s own protection, which leads to tanning

In addition to the types of damage listed above, UV radiation, especially UVA radiation, is also responsible for other health problems. These include sun allergies, dermatoses, Mallorca acne and snow blindness. The term "sun allergy" is really a colloquial expression that is used as a kind of umbrella term covering very different skin reactions associated with sunlight. In extreme cases, some people are unable to tolerate any UV light at all and have to stay indoors during the day. And while the focus of this article is not on the problems associated with UV light, we will make this the subject of a future article. 

Our focus here and now is primarily a type of radiation that is not so frequently mentioned when talking about sun protection: infrared radiation (IR). In contrast to UV rays, which are not visible or directly perceptible, IR radiation is clearly noticeable. Our body absorbs its energy and the molecules start to dance around. The result of this is heat. In other words, this is exactly the reaction we associate with the sun – it warms us. Although a large part of the absorption of IR-B and IR-C radiation already takes place on the surface of the skin (epidermis), the heat seems to find its way effortlessly to the center of the body. Some forms of medical treatment exploit this way of working. For example, we're sure at least some of our readers will have used a heat lamp to treat back pain.

If you would like to find out more about IR radiation or heat radiation, the German Federal Office for Radiation Protection (BfS) publishes plenty of interesting material on the subject. 

Incidentally, many people still believe it is actually these hot IR rays that are responsible for sunburn. Simply because they are hot.

Our colleague, Professor Bernd Herzog PhD, explains why this is not the case in the video beside.

Prof. Dr. Bernd Herzog: Heat from sunrays equals sunburn. Right?

Our skin is our thermostat 

Our early ancestors had few tools to protect themselves from heat and cold. The skin makes an important contribution here: it ensures the body can maintain a constant temperature. If the ambient temperature drops, small blood vessels in the upper layers of the skin contract and release less heat. This prevents the body from cooling down. For a similar reason, we have goosebumps when it is cold: the tiny muscles controlling the hair follices contract. 

At high temperatures, this mechanism works the other way around, allowing the blood vessels to expand. The blood cools down and the body temperature drops. In addition, the sweat glands produce a fluid that is released on the surface of the skin. The cooling effect of this liquid evaporating also cools the body. 

Our skin is our shield against fluid loss 

Even if it doesn't look much like it, the human body consists of almost two thirds water. This is why a significant loss of water would be life-threatening for us. The skin helps to prevent this happening. It only releases as much moisture as is required to regulate body temperature, equating to about half a liter to one liter per day/night. This amount may increase many times over if we exercise. 

Despite all its various natural protective mechanisms, though, the skin can only go so far as a protective shield. If we are exposed to the sun’s hot rays for a long time, the skin is exposed to stresses it can no longer regulate on its own.


When the sun strikes 

Let’s take a look at drivers of convertibles for a moment. They cruise around all day long, enjoying the blue sky, the bright sun and the cool moving air. Wonderful. Back home in the evening, they pay the price for forgetting to wear a cap or a hat: sunstroke. Oh, and drivers of convertibles should also be using enough sunscreen to avoid sunburn.

This type of heat damage occurs when the head, throat and neck have been exposed to sunlight and IR radiation for a lengthy period of time. Heat radiation, which is simply too intense when sunstroke occurs, irritates the cerebral membrane, or meninges, and in the worst case can even cause inflammation. 

This is the recipe for having a bright red head at the end of the day. Dizziness, headaches, nausea and slight confusion can create a feeling of discomfort. Although your body temperature may feel higher, sunstroke does not cause a rise in temperature. In extreme cases, it may lead to unconsciousness or a cerebral edema. 

Although we have used drivers of convertibles as an example, it is actually babies and toddlers who are most at risk of sunstroke. Older people and those with bald heads are also more susceptible. 

The right response 

If the symptoms start while you are still on the road, you should get out of the sun immediately. Applying a cool towel to the head and neck can provide quick relief. In addition, it is important to drink plenty of lukewarm or slightly cool liquids. No ice-cold drinks, even if they may seem very tempting. If there is no improvement after a while, it is a good idea to see a doctor. Children with suspected sunstroke should be taken to the doctor straight away. They can be much more sensitive to meninges irritation than adults. 

In addition to sunstroke, there are other forms of heat damage that can stress and injure the body. Heat cramps, for example, mean the body has lost too much fluid and especially salt, causing the muscles to twitch and cramp. Drinking salty drinks helps prevent this and can also help once the first signs are detected. A rise in body temperature can cause heat exhaustion, and in severe cases heatstroke may occur. 

Prevention is better than cure 

Although IR radiation does not cause sunburn, we still need to protect ourselves from it. In this case, however, we can't rely on the usual sunscreens and creams for protection. Wear a hat, stay in the shade or a cool room, and make sure you drink plenty. It is not a good idea to walk around in the strong midday sun at lunchtime unless you have to. 

Plan your time in the sun and take care of yourself. After all, we all like to enjoy the sunny days without worrying.