Here’s the Science Behind How Freckles Appear on the Skin

Many people have a fairer complexion while some have additional tiny darker spots on their face which are termed as freckles.
Freckles are small areas on the skin where melanin pigmentation is much higher. Melanin is a protein that is responsible for skin pigmentation as well as eyes and hair. This protein is also responsible for protecting the skin against UV exposure from sunlight.
‘Freckles appearance depends on a gene called MCIR. An active MCIR gene produces eumelanin leading to darker skin while an inactive gene produce pheomelanin leading to fairer skin, blonde or red hair and a propensity for freckles.’
People with freckles have tiny spots of melanin while people without freckles have even melanin spread. The tiny spots containing higher amounts of melanin gets darker due to sunlight exposure and becomes fainter with lesser sunlight.
The cause of freckles is attributed to be genetic where a gene called as MC1R instructs cells to produce melanin. This gene is responsible for production of a type of melanin called as eumelanin.
Melanin is produced by specialized cells called as melanocytes. There are two types of melanin which is responsible for different colored skin tones. Eumelanin is dark brown to black color while pheomelanin is red to yellow in color. Therefore, an active MC1R gene will produce more of eumelanin leading to darker skin while an inactive gene will produce more pheomelanin, increasing the chances of having a fairer skin, red hair and freckles.
MC1R is said to be responsible for two traits namely red hair and freckles. Freckles is a dominant trait while red hair is a recessive trait. Not all people with red hair have freckles nor all people with freckles have red hair.
Freckles is considered to be similar to a condition called as lentigines, which form because some people contain more melanocytes in their skin. Dark spots in freckles are temporary while they are permanent in lentigines.