I woke up this morning, wandered into the bathroom, happened to glance in the mirror as I yawned... and stifled a gasp. Aaargh! My tongue was BLACK! Yes, black. I leaned in closer, sticking out my tongue to examine it, my mind racing. It looked like I had spent all night sucking on licorice. I had no idea what had caused it, "Could it be some weird fungal infection?" Other than the color, I looked, and felt healthy. I grabbed my toothbrush and took an experimental stab. It seemed to work. I added toothpaste and scrubbed my tongue for a minute before rinsing and inspecting. Phew! I breathed a sigh of relief- my tongue looked normal again, but still- what had caused this?
After dressing, I went down to my computer where Google once again came to my rescue. I typed in "I woke up with a black tongue", and to my surprise, I got an immediate hit. Several of them in fact. It seems that "black tongue" is a little known side effect of chewing on Pepto Bismol tablets before bed. There is an active ingredient in the medication that reacts with sulfur to create the black substance. I had taken a couple of tablets last night to combat some bloating, so it was obvious that the Pepto was the cause of my alarm.
On further reflection, I could have probably used this information in my "fake sick day" arsenal 20 years ago. There were several occasions when I could have used one more day for studying, or to finish a report.
At any rate, just remember this the next time you wake up with black tongue. Be reassured that you are not dying of some weird disease, or fungus- it is merely an embarrassing (and a little gross) chemical reaction in your mouth!