How often should sunscreen be reapplied when spending time outdoors?

Reapplying sunscreen every two hours is essential for maintaining effective protection against harmful UV rays, especially when spending time outdoors. Sunscreens can wear off due to various factors such as sweating, swimming, or simply the passage of time, which diminishes their protective qualities.

Applying sunscreen at the beginning of the day is not sufficient to ensure ongoing protection throughout outdoor activities, as the effectiveness diminishes with exposure. While some individuals may believe that reapplying every 30 minutes is necessary, this can lead to an over-application that is often unnecessary for most activities unless in a very high UV index environment, participating in sports, or swimming.

Daily application at night does not provide benefits, as sunscreen is designed to protect the skin from UV exposure, which is primarily a daytime concern. Therefore, the recommended guideline of renewing sunscreen every two hours strikes a balance between maintaining skin protection and practicality during outdoor activities.