My Tongue Is Burning Around The Outer Edge; The Insides

My tongue is burning around the outer edge; the insides of my lips were similarly burning for a few days, but they have quit. this has been going on for about a week, maybe ten days.
I've been waking up in the mornings with a particularly dry mouth, especially (it seems) a spot under my tongue on the right, aft.
The only recent change is that I've started taking citalopram.
WTH?