DefinitionPatchy skin color refers to areas of irregular skin coloring. Mottling or mottled skin refers specifically to blood vessel changes in the skin which cause a patchy appearance.Alternative NamesDyschromia; MottlingConsiderationsIrregular or patchy discoloration of the skin can be caused by:Changes in melanin, a substance produced in the skin cells that gives skin its colorGrowth of foreign organisms on the skinBlood vessel (vascular) changesThe following can increase or decrease melanin production:Your genesHeatInjuryExposure to solar or ionizing radiationExposure to heavy metalsChanges in hormone levelsExposure to sun or ultraviolet (UV) light, especially after taking a medicine called psoralens, may increase pigmentation. Increased pigment production is called hyperpigmentation.D