I was prescribed Beta Blockers to combat nervousness which lead to facial sweating but they didn't really work. I thought they did in the beginning because of the "placebo effect" (thinking they would work gave me more confidence) but they're not really the answer. They don't actually stop you sweating, only slow down the heart rate which, in theory, "calms you down".
I swear by Anhydrol Forte, an anti perspirant (maximum strength) which comes in roll on form. You put it on at night, lean your head right back and roll it across the forehead and hairline (so it doesn't drip into the eyes) and smooth it evenly with one finger. It dries into a crystalline powder which can sting a bit at first. You wash it off in the morning. You need to apply it every night for a week in order to form the pore blockage and after that you top it up every other night or every third night, it's up to you.
It really works. When I do extreme sports I sweat everywhere on my body as I would expect but my head is completely dry. Knowing this has given me confidence in social situations I thought was lost. It's just good to know that, no matter what, you are not going to visibly sweat. Over time, being in more and more social situations, you will regain confidence again and may not need to use it so much.