Why do some people have freckles and what causes them?

There are actually 2 types of freckles, Ephiledesand Lentigines. Ephilides is a genetic trait*, found in people with fair skin and red hair. Lentigines are formed after long years of exposure to the sun. Anybody who doesnt have freckles and are under the age of 19 either a) Doesn't go outside much or b) doesnt carry the genetic trait* *The genetic trait is the MC1-R gene, which is dominant