As someone who has suffered from extreme acne during the teenage years of her life, I can tell you that sunlight was more of a friend, than an enemy. Sunlight has a positive effect on acne, as well as, acne scarring and I will you why.
I would break out constantly during my teenage years due to stress and hormonal changes in my life. In fact, I was going through a lot changes, that highly contributed to acne. This excluded genetics, of course which also play an immense role on breakouts. When exposed to sunlight, I've noticed that my acne would go away and the scars would fade daily. Of course, I did other things, but in my mind, I didn't understand why the sun was actually helpful and beneficial towards my skin.
One evening, I decided to log online a few years ago and research "Is the sun good for acne?" and found out that when we are exposed to the sun, we are exposed to vitamin D. Vitamin D is very important, as it prevents a variety of illnesses and cancers. Our skin is the largest organ we have. What I found out recently is, vitamin D from UV-B Rays some how enters your body and some how transforms into your entire body, effecting all of your organs including our skin, our largest organ. This includes everything from your bones to your blood to your liver to even your hormones.
Then it hit me. Hormones are a big contribution to acne. Stress and environmental factors also contributors to acne too. Then it hit me, sunlight is important to treating acne the way a plant uses photosynthesis because it releases a vitamin that triumphs all organs and benefits them, including hormones, stress and any problems caused from the environment.
I think that is why some individuals believe the sun is responsible for acne when it fact it is more helpful than hurtful.