How often should sunscreen be reapplied when outdoors?

Sunscreen should be reapplied every two hours when outdoors to maintain optimal protection against ultraviolet (UV) radiation. This time frame is based on recommendations from dermatologists and skin care professionals, as it allows for replenishment of the sunscreen’s active ingredients, which can break down over time due to sun exposure, sweating, or swimming.

Reapplying every two hours is especially important for individuals who are swimming or sweating heavily, as these activities can reduce the effectiveness of sunscreen. While some formulations may advertise longer-lasting protection, two hours is a standard guideline to ensure adequate coverage.

In situations like swimming, it's necessary to use water-resistant sunscreen and also reapply it immediately after swimming, towel drying, or perspiring, further emphasizing the importance of regular application for maintaining skin protection.