No! SPOTs are designed to last through multiple sunscreen applications. The colour change is reversible, and SPOT will be accurate for an entire day of activity.We recommend that each person uses ONE SPOT PER DAY. If a SPOT changes to purple, and you apply sunscreen over top of it, it will change back to clear and let you know that you're safe again. At the end of the day, remove your SPOT and throw it out!