Hi..
Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain it seems that the dark coating over the tongue seems to be
Black Hairy Tongue and it can be due to accumulation of dead cells and debris over the tongue..
It can also be due to any medication or any coloured food, so coloured mouthwash can be a culprit..
It can also be due to bacterial or fungal overgrowth over tongue..
I would suggest you to gargle with a 1:1 solution of
hydrogen peroxide and water..
You can also use a tongue cleaner to clean the tongue..
You can dip brush in 1:1 solution of hydrogen peroxide and water and gently clean the tongue..
You should also chew raw fruits and vegetables as it cleans the tongue by frictional action..
Limit intake of tea and coffee..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.