How to apply sunscreen: a practical guide to slowing photoaging

From sunscreen selection to reapplication every three hours, the basics matter most.

Sunscreen is one of the most practical steps for slowing photoaging. UV exposure can cause more than temporary redness; over time it may contribute to pigmentation, dryness, fine lines, uneven tone, and reduced skin resilience. After skin treatments, sun protection becomes even more important because post-treatment pigmentation can be harder to manage.

Photoaging builds up through daily exposure

Strong sunlight may cause acute redness or peeling. Repeated low-level UV exposure can also reduce skin hydration and contribute to wrinkles, spots, and dullness. This is why Korean dermatology guidance often begins with daily sunscreen habits.

Amount and reapplication matter more than branding

Sunscreen should be applied generously and evenly. For the face, a coin-sized amount is a useful reference. When staying outdoors, reapplying about every three hours is a practical standard. Over makeup, sunscreen sticks or cushion formulas can make reapplication easier.

Choose sunscreen by skin type

When shopping for sunscreen, SPF and PA ratings are not the only criteria. Oily skin may prefer a lightweight gel or lotion, dry skin may need a moisturizing cream, and sensitive skin may benefit from a low-irritation mineral sunscreen. The neck, backs of the hands, and areas around the ears should also be covered.