How frequently should sunscreen be reapplied?

Sunscreen should be reapplied at least every 2 hours to ensure optimal protection against harmful UV rays. This is particularly important because sunscreen can wear off due to various factors, including sweating, swimming, and the natural breakdown of active ingredients over time. Reapplying every 2 hours helps maintain a consistent level of protection on the skin.

In addition to this regular reapplication, it is also advisable to apply sunscreen after swimming or excessive sweating, as these activities can reduce the effectiveness of the product, despite it being labeled as water-resistant. However, adhering only to reapplication after swimming would not provide comprehensive protection throughout the day.

Furthermore, while reapplying every hour may seem beneficial, it is often unnecessary and may lead to waste without allowing the skin's protective agents sufficient time to adhere properly. Reapplying every 4 hours may also leave a gap in protection during peak sun exposure times, which is why the recommendation is structured around the 2-hour mark. This frequency is a standard guideline provided by dermatologists to ensure skin remains adequately shielded from the potential damage that UV rays can cause.