There are some easy steps you can take in order to help prevent freckles from getting darker and prevent future freckles from forming altogether. Here’s a hint: It’s all about sun protection.
Use a broad-spectrum sunscreen with an SPF of 30 or greater everyday (even if it's cloudy). Apply it generously and frequently to all areas of skin that are exposed, and don’t forget to reapply every two hours, and after you go swimming or have been sweating.
You may also notice that your freckles tend to fade come wintertime, and this is completely normal as well, according to Harvard Medical School. Just continue to wear your sunscreen for freckles to prevent them from coming back with the warm weather.
Source: L'Oréal