Avoiding excessive sun exposure is important at all ages.
However, the earlier in life your skin is exposed, the more time the damage will have to accumulate. Moreover, stem cells in the upper layer of the skin of children (which are those cells that might be responsible for skin cancer) are closer to the skin surface compared with those in adults, making children more sensitive to exposure to ultraviolet (UV) radiation. Also, during childhood and adolescence, body tissues are growing and developing rapidly. Because of this rapid growth, cells in young people are even more vulnerable to damage from the sun. Adults (parents, family members, teachers, etc.) should help children to avoid too much sun.
For children up to 1 year old, it is recommended to avoid all direct exposure to sunlight, for example by providing shade when they are outdoors.