The sun can be dangerous for our skin leading to sunburn if the time, your skin is exposed to the sun, is more than it is allowed. If you expose your skin, that has already been tanned, to the sun, the possibility of getting sunburn is almost excluded. People, who have fair skin, have difficulties with getting a tan, but can be easily sunburned. To avoid getting sunburned one should use a sunscreen. 

It is necessary to differentiate between a tan and a burn and the beneficial effect of a sunscreen. It is also important to know the skin’s structure.

Skin is an organ or a differentiated structure that consists of specific cells and tissues and that defends human body from the environment. Skin has sensors and layers; it can suffer from abrasion and sunlight.
Skin consists of two main layers: the epidermis on the outside and the dermis on the inside.

The epidermis is the barrier, while the dermis is the layer that contains nerve endings, sweat glands, hair follicles and so on.

In the subcutaneous layer there are the blood vessels that supply the sweat glands, hair follicles, sebaceous glands and erector muscles with blood.

Blood vessels belong to the dermis's capillary bed. The dermis is full of capillaries that provide nutrition to the cells in the dermis and have the function of cooling. The epidermis is not supplied with blood, but it is fed by the dermis.

The dermis consists of sweat glands, hair follicles, nerve endings and so on.

One can differentiate the following types of nerve endings that help to sense the world and defend people from getting burns, punctures and other possible damages of the skin:

* Heat sensitive
* Cold sensitive
* Pressure sensitive
* Itch sensitive
* Pain sensitive

The epidermis consists of two main layers, the inner of which is living and the outer of which is dead. The dead skin cells of the outer layer are constantly flaking off and are replaced by new cells.

The living, inner layer is the malpighian layer, it contacts with the dermis, supplies it with the nutrition. The malpighian layer produces the dead cells that flake off. When our skin is exposed to the sun, the sun affects the malpighian layer of the skin.

There are such layers of the malpighian layer:

* The first level is the basal layer that contacts with the dermis directly. Such illness as a basal cell carcinoma (cancer) is started from the basal layer.
* The next layer is the spinous layer.
* The spinous layer is covered with the granular layer.

The granular layer is covered with the stratum corneum, the outer layer of dead cells that can be seen. The cells in this layer are filled with a tough protein called keratin. Keratin is available in horns, hair, hoofs, fingernails and feathers.  Skin is made of a thinner and more flexible layer of the keratin, that’s why it is tough.

In palms and feet the stratum corneum is also obvious, but it is thicker to handle the abrasion from constant wearing.
The malpighian layer consists also of a melanocyte which produces melanin, a pigment that is necessary for tanning.

Melanocytes can be the cause of the cancer called melanoma that is the result of UV radiation damage made to melanocytes. Repeated exposure to UV can lead to cancerous mutation.