Many people believe that freckles come from increased sun exposure. Some believe that freckles are a trait you're born with. Both answers are correct. Well, mainly the second answer, but the first guess isn't too far off. When in direct sunlight, our skin is protected by a chemical called melanin. Melanin helps to increase the pigment on the skin. Freckles are simply spots where melanin has built up. The build-up is caused by the clumping of melanocytes (they produce melanin) on the skin. People with an even spread of melanocytes, when exposed to UV light from the sun, will burn and tan nicely and evenly. Other people tan just a little bit more at those small clumps and it seems as though their freckles have grown and intensified. Thats the reason behind the common misconception of sun-caused spots. But what actually causes freckles?
Scientists have found the gene that regulates freckles and, not so coincidentally, it also controls the appearance of red hair. This gene is labeled MC1R. The MC1R gene is responsible for creating the MC1R protein that creates and protects the most common skin pigment, eumelanin. When the MC1R gene is broken, it overlooks the other pigment known as pheomelanin and the freckles and/or hair turn red. There are many variables to consider when trying to figure out why someone has red hair and no freckles or vice versa. The easiest and most likely answer is that there is actually another gene in collaboration with MC1R that helps make that decision.