Do you have freckles? If you don't, chances are you probably know someone who does. But what are they exactly?
Freckles are just skin cells that contain a pigment (color) called "melanin." Melanin is a chemical made by skin cells called "melanocytes." Melanin helps to protect the skin from the Sun's harmful ultraviolet rays by reflecting or absorbing them.
While anyone can have freckles, they are genetic. So if your parents have freckles, there's a good chance you will, too. People with fair complexions (skin and eyes that are light in color) tend to have more freckles than people with darker complexions.
People with fair complexions have less melanin in their skin to start with. When sunlight causes their melanocytes to make more melanin, they often develop freckles instead of getting an even suntan like people with darker complexions.
Some people have freckles that fade away in the winter and return every summer. Other people have freckles year-round. Freckles often tend to fade when people get older.