Dark spots on your skin usually are the accumulation of dark pigment just underneath your skin. These can appear for several reasons and can develop anytime from birth to old age. However, the reasons for the development of dark spots can vary. Identifying these skin discolorations and understanding how they develop can help you determine whether a trip to the doctor or dermatologist is necessary.

Blood Vessel Deformities

Many newborn babies have a discolored, dark spot on their skin. These common birthmarks can sometimes occur for reasons doctors and dermatologists do not yet understand, but one of the reasons they do develop is due to blood vessel deformities located under the skin where the spots appear, according to Discovery Health. These can develop within the first month of development. Some will go away over time while others will stay, but all marks of this kind are harmless.

Melanin Coagulation

Moles are another common skin development that many consider birthmarks, even though they can change size and shape over time. Moles tend to be brown or black and either flat on the skin or raised 1. They are darker than a normal skin discoloration and develop with melanin--the pigment of your skin--coagulates. Moles sometimes can indicate possible cancer in the skin, particularly if there is a change in color, but they also can be removed easily with a laser.

Sunlight Exposure

Sunlight can produce dark spots on the skin in a couple of different ways. The most common of these is age spots--sometimes called liver spots--which develop when sun exposure damages the pigment-producing melanocytes in your skin and causes a spike in production, according to Discovery Health. Sunbathing or exposure to sunlight also can stain your skin when pregnant or taking medications that imbalance your hormones and cause unstable and uneven melanin production at various spots on your skin--the sunlight activates the melanin in these locations, darkening the skin.