Freckles can be more noticeable when you are exposed to direct sunlight. This is because when the epidermis, the outermost layer of the skin, gets contacted with ultraviolet (UV) rays, it thickens and cause the pigment-producing cells to produce more melanin, which makes the freckles on your skin darker.
Freckles may also appear on children as young as one or two years old and it may develop on places where it is likely to be expose to the sun such as the body, face and arms.
However, freckles can also be caused by genes. If your parents or siblings have them, it is more likely you will have them as well. Those with fairer skin and light or red hair are more likely to have freckles than those with darker complexion.