Why is it stated if you have had skin cancer then to avoid red light therapy?

I really want to purchase a Baby Quasar Plus for wrinkles, and possibly one for acne. I have read on reviews not to use the red light if you have skin cancer. I have had past melenomas (on arm and back) but not on my face. What are the risks? Just curious as I am not able to find any details- in fact I have read that red light therapy can be used as a treatment. Thanks!