After some internet research, I determined that I am not alone. It is actually from the 3M dust remover Justin used to clean my laptop this morning! According to 3M's website, they put a bittering agent in the canned air to discourage
It was kind of funny looking through people's thoughts about what could be causing it. Some of my favorites: (1) being poisoned; (2) having gastro-esophageal reflux disease; (3) taking Vitamin D or acai berry; (4) using acne medication; or (5) having liver disease.
I did not take the advice of many people who recommended you lick the keyboard to see if it's bitter. Um, no thanks. I did, however, already take 3M's advice and wiped down the keyboard with isopropyl alcohol and water. I am just glad the mystery is solved!