The length of time your tan will last depends on how well you prepared before the session, and how you take care of your skin after the session. The most important aspect is to exfoliate before the session. The shallower the dead skin layer is, the longer it will take to fully build up and shed off. This means that the more perfectly you exfoliate your skin before spray tanning, the more even your tan will be and the longer it will last before fading. Additionally, moisturizing your skin every day will prevent premature exfoliation through drying. Ask a staff member which exfoliants and moisturizers are suggested to get the best results.
