Children’s skin, like many of their organs, is still developing and so they are more sensitive to sunlight. Young skin is thinner than adult skin and its barrier function and self-protection mechanisms (especially melanin synthesis) are not fully developed. The surface area to volume ratio is also much higher in children’s skin.Sun-induced skin damage incurred during childhood puts someone at a much higher risk of further skin damage in later life.  You can read more in the effects of sun on children’s skin.