I would like to ask about the cause of freckles.

Hello. I'm posting this because I have a question.

My freckles seem to be getting worse. What is causing them?

I thought the cause of freckles was simply exposure to too much sunlight, but when I saw a coworker, she said she had a severe freckle called Ota nevus since she was young.

Of course, it is important to get rid of freckles once they appear, but I think it is also very important to know the cause of freckles and prevent them.