All sun exposure causes some damage to your skin. Usually, your body is able to repair the damage. However, if the damage is severe, this becomes increasingly difficult.
It is difficult to give a precise definition of “too much sun” because this depends on personal characteristics such as your skin type, the strength of the sun, and your location (ultraviolet index; UVI). The amount of damage increases with longer duration of sun exposure, and the damage will be more intense if exposure takes place when the sun is very strong, such as around noon, during the warmest time of the day (e.g. between 11:00 and 15:00) and in the summer months. For example, at a UVI of 6, which is easily reached at noon in spring and summer, a person with skin type 1 or 2 will suffer from sunburn in 10–15 minutes.
If you go out into the sun, you should make sure that you protect the most frequently exposed parts of your body, such as your face, neck, and hands. If you are sunburnt, you have certainly been exposed more than is safe. However, even before you become sunburnt, you may have been excessively exposed. Frequent sunburns, especially during childhood and adolescence, are related to a marked increase in the risk of developing skin cancer later in life. But all exposures to ultraviolet (UV) radiation, at any age, increase your risk of skin cancer.