Dark skin spots
Dark skin spots may be caused by many factors and skin diseases.
Melasma is a disease characterized by dark spots, usually in face. Its occurence its related to hormonal factors (pregnancy, contraceptives), genetic factors and has as a triggering factor the light exposure (sunlight and visible light).
Solar melanosis (senile spots)
Senile spots, or solar melanosis, are provoked by sun exposure though years and due to this are more common in advanced age. They are brown color spots, in variable sizes, that shows up in areas exposed to the sun, such as back of the hands and arms, neck and shoulders. They are more frequent in light skin individuals.
Freckles are dark, brown, spots, punctate (precise limits) that cover specially the face, shoulders, arms, legs and anterior and posterior thorax, which are areas more exposed to the sunlight. Freckles exhibit a hereditary characteristic, because they are more frequent in people with white skin and light eyes, which are more sensitive to sunlight. The peak in the appearing of freckles occurs in adolescence and goes until adult age, when they usually decrease.