Some button batteries taste terrible

I don't use button batteries very often, so I was surprised to note the information on the packaging, which apparently is a new development this year.  The batteries are not only in child-resistant packaging, but they also taste bitter, and stain the mouth a bright blue color.

I knew ingesting button batteries was dangerous, but I didn't realize the rapidity of the toxicity: 

Ingested coin or button batteries result in thousands of emergency hospital visits each year, according to the U.S. Consumer Product Safety Commission, which notes that “the consequences of a child swallowing a battery can be immediate, devastating and deadly.”

“A button cell battery can burn through a child’s throat or esophagus in as little as two hours if swallowed,” according to the agency.

Detailed information is available from Energizer.  Their FAQs indicate that the reaction time (taste and color) are immediate, and that the blue dye is food grade.  I was seriously tempted to lick one, but I'll leave that up to some adventurous reader.