Freckles are basically an uneven tan! They are also not harmful or the sign of a health problem. They’re just small batches of pigment cells (cells that contain color) called Melanin (say: MEL-uh-nun) that are contained within the skin.
Melanin helps protect the skin from sun damage by reflecting and absorbing ultraviolet (UV) rays. When these rays hit your skin, the Melanin cells in your skin respond by releasing their chemicals which darken your skin and protect you better from the sun.
The more melanin you have in your skin, the tanner you look! In some people, the Melanin tends to “clump” in areas which appear darker than the skin surrounding them. This is how freckles come about. When you spend lots of time in the sun, these clumps of melanin are stimulated to produce more pigment thus you get darker, or even more freckles! That’s why being outside in the sun may help cause freckles or make them darker.
Freckles are usually tan or light brown, flat, and very small (smaller than the head of a pin). Sometimes they overlap and run together so they may look larger. Some people have freckles that fade away almost completely in the winter and return in the summer. Other people’s freckles don’t change much with or without the sun and can be seen year-round. Freckles also tend to fade as people get older.
The tendency to have freckles is genetic (passes from parent to child) and tend to be inherited. So while anyone can have freckles, if your parents have freckles there’s a good chance you will, too. Also, people, especially kids, who have fair complexions (that means their skin and eyes are light in color) are much more likely to get freckles than people with darker complexions.
People with light skin have less melanin in their skin to begin with, but they seem to make more melanin when exposed to the sun. So instead of easily getting an even suntan, they sometimes get freckles.
Answer provided by Discovery.com