An ephilide is a flat freckle, which may occur in areas of your skin where there is an excessive amount of concentrated melanin (skin pigment). These darkened hyperpigmented lesions are most often noticeable in people with a fair complexion (Fitzgerald Classification I and II). Other names for freckles are ephelis, speckle, fleck, dot, spot, mole, blotch and macula.
Ephilides are quite common and our found in people with varying ethnicity. However, you can definitely be genetically predisposed to being born with ephilides or developing them over the course of your life. One specific gene related to the predilection towards developing ephilides is called the melanocortin-1 receptor MC1R gene variant. Those genetically predisposed will likely develop ephilides after exposure to sunlight. Natural sunlight contains specific light frequencies call UV-B which then activates your melanocytes (melanin producing cells) to produce melanin and hence cause the development of ephilides in areas where you have excessive melanin (skin pigment)
Ephilides are predominantly found on areas of your skin that are frequently exposed to the sun. These susceptible locations include your face, arms, and shoulders.
Since ephilides occur largely because of sun exposure, they tend to increase as you age. Therefore, ephilides are rare in infants and young children. Ephilides can lighten and darken depending on how much sun exposure you have and whether or not you have used some sort of skin lightening agent.