[Misc] How do you know if a product is responsible for breaking you out?

Beauty Tips For Body Care
I started Chantecaille's Just Skin Tinted Moisturizer 3 weeks ago and really loved it. My sample ran out, and a few days later, I had 2 big cysts on my forehead. Is it possible it's from the moisturizer, even though I had stopped using it? Nothing else in my routine has changed. Thank you!
Girls Blog 2015
Submitted by sanantoniojackson