How long should I wait after a spray tan before showering? To give the DHA enough time to fully set, it is recommended to wait a minimum of 8 hours after a sunless spray tanning session or 24 hours for optimal results. Showering sooner may diminish the intensity of the tan. If you tan using an Instant Cosmetic bronzer, the instant cosmetic color will wash off in the shower, but the color produced by the DHA will remain.