Causes of Excessive Sweating

Kiwi is my bird-o asked:

I used to sweat so freaking much. It was aweful, I would have sweat rings down past my boobs in the middle of winter while I was freezing from the moisture on my sweater. After even the prescription antiperspirants didn’t work, I just switched to using an all natural deoderant (figured there was no point in possibly getting lymphnodic cancer from antiperspirants for nothing). Soon after I started using the natural deoderant, the sweating stopped. It’s been several years now, and I barely ever sweat unless it’s hot or I’m working out.

Lately, I have been starting to notice the excessive sweating starting again (not as severe, but still embarassingly noticeable). Any idea why it’s starting again, what causes it, and how to naturally stop it? And I wont ever use antiperspirants again either, too toxic.