Black freckles are caused by repeated exposure to sunlight just as any other colored freckle. Freckles may be black, brown, reddish or yellow depending on the color of the surrounding skin. Freckles usually become darker after more sun exposure and lighten with less exposure as in during the winter.
Freckles are small spots of melanin on the skins of people with fairer complexions and blonde or red hair. People with fair skin do not usually produce enough melanin so the skin does not color evenly when exposed to sunlight. When the sun penetrates the skin, melanocytes are activated and, because of the dominant melanocortin-1 receptor MC1R gene variant, freckles are formed. The tendency to freckle is genetic and often runs in families.
There are two types of freckles: ephelides, or simple freckles and lentigines, or sunburn freckles. Black freckles may be simple freckles, which are usually tan or light brown, after a summer of sun exposure in which the melanin darkens just as skin does when tanning. This type of freckle will usually fade to a lighter color during the cooler months or if sun exposure is avoided. Ephelides are small, round and uniform.
Lentigines tend to be larger and darker with irregular borders and may appear as black freckles. They are more common on the shoulders and upper back as these areas of the body are more prone to severe sunburn. They do not tend to fade but, as long as they do not change, are just as harmless as the ephelides. Black freckles may also develop in adults as liver or age spots which are also harmless.
People who freckle have skin that is highly vulnerable to sunburn and skin cancer. While freckles themselves are harmless, any change in their appearance should be checked. Skin cancer commonly manifests itself in a change in the appearance of the skin such as an irregularity in a mole or freckle, a new growth or a sore that does not heal. Any suspicious moles or freckles should be checked by a doctor.
The only way for genetically predisposed people to avoid freckles is to completely avoid sun exposure. Wearing a high factor sunscreen will help in the suppression of the production of freckles, but not completely. Anyone who will have sun exposure should use high factor sunscreen in order to protect the skin from skin cancer. For those with freckles who wish to reduce their appearance, there are safe methods to lighten them.