Irregular or patchy discoloration of the skin can be caused by:
- Changes in melanin, a substance produced in the skin cells that gives skin its color
- Growth of bacteria or other organisms on the skin
- Blood vessel (vascular) changes
The following can increase or decrease melanin production:
- Your genes
- Exposure to radiation (such as from the sun)
- Exposure to heavy metals
- Changes in hormone levels
Exposure to sun or ultraviolet (UV) light, especially after taking a medicine called psoralens, may increase skin color (pigmentation). Increased pigment production is called hyperpigmentation.
Decreased pigment production is called hypopigmentation.
Skin color changes can be their own condition, or they may be caused by other medical conditions or disorders.
How much skin pigmentation you have can help determine which skin diseases you may be more likely to develop. For example, lighter-skinned people are more sensitive to sun exposure and damage, which raises the risk for skin cancers. However, too much sun exposure can lead to skin cancers even in darker-skinned people.
Generally, skin color changes are cosmetic and do not affect physical health. However, mental stress can occur because of pigment changes. Some pigment changes may be a sign that you are at risk for other medical disorders.