Quoting [JadeLee]:" I am going to pull the "it depends" out. Someone who puts a drop is more than likely not going to hurt ... [snip!] ... make them really sick. If it gets to the point of a kid getting repeatedly sick over it then yes it is abuse at that point!"
My mom used to threaten us with it, until I asked her to do it one day (I could be a little ass sometimes) and she shut up and never brought it up again. My mom never physically disciplined us.
I wouldn't call CPS on someone who washed their kid's mouth out with soup for biting or cursing, just like I wouldn't call CPS for a parent spanking or popping their child with an open hand.