Most dancong doesn't have a heavy roast; usually a high amount of oxidation and a traditional, but not heavy, roast.
Could be just too much hot qi (whether in the tea or something else). Pomelo, cold qi tea, or other cooling stuff might help. Eating things like mango, lots of spicy food, etc. may do the opposite.
If you use toothpaste with sodium laurel (or laureth) sulfate, try switching to an SLS free brand.