Without sunscreen, SPOTs can change from clear to purple in approximately 30 seconds in direct sunlight! With sunscreen, the reverse change from purple to clear can take up to 1.5 minutes in direct sunlight.With sunscreen applied to SPOT, there are many factors that affect the speed of the color change:UV index Time spent in the sun vs. shadeYour sunscreen's SPFHow much sunscreen you appliedHow long you let your sunscreen dry on your skin and SPOTActivities you're doing (swimming, sweating, sunbathing, etc.)All sunscreens recommend to reapply after swimming or toweling, so expect to see a color change when you get out of the water.