For a very long time organisms lived only in water. Life on land has only been in existence for around 400 million years. Due to the dryness of the environment, nature developed a variety of systems to protect the skin from drying out. In humans, it is the skin which has taken on this function. The skin – which can also be described as a cover organ – is the largest human organ and the richest in nerves. Depending on the size and scale of the body, it weighs up to 10 kg and covers an area of 1.5 to 2 m2. It keeps the inner organs from being injured or drying out. It also serves to protect the human body against environmental influences such as UV radiation from the sun, and takes on major functions in terms of the metabolism and immunology. In this way the skin is involved in fending off diseases.

The skin also takes on an important task in regulating body temperature. When it is hot, sweat on the skin evaporates and thus contributes to reducing the body temperature. The other way round, when it is cold less sweat is produced and warmth is retained in the body.

In addition, the skin takes on a major role in transmitting sensory impressions such as temperature, touch, pressure or pain

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