How I would sign this case out: Not a human Parasite
My best guess at what this is: chewing gum. Unusual, yes, in an 18 month old, but we don't know the full story, and we all know how kids like to sample their environment by tasting...
As G.P. said, "If it's chewing gum, there's only 1 way to find out..."
And some accuse ME of being gross.
Thanks for all of your comments! (you too G.P.)