According to the search results, sunscreen should be applied before primer. Sunscreen acts as a protective barrier while primer helps to create a smooth canvas for makeup application. By applying sunscreen first, you can effectively shield and care for your skin while still achieving a flawless makeup look. It is recommended to wait for a few minutes before applying primer to allow the sunscreen to penetrate the skin. Applying primer before sunscreen could interfere with how well the sunscreen adheres to the skin and reduce its effectiveness.