I'm 22 yrs old female and I've had this brown spot under my tongue, and now i see similar spots over the side of my tongue. I'm confused as to what they're. And recently I've been to dentists too, for tooth extraction and filling. But none of them suggested anything. Like if those spots were danger to me or not. I've been an active smoker and recently am trying to quit it. I'd really like to know if those brown spots are dangerous for me.