Christine Allen, 32, faces two counts of aggravated assault and two counts of administering a noxious substance with the intent to harm.
Family and friends of one of the alleged victims were on hand to witness the hearing.
Police accuse Allen of feeding two children tetrahydrozoline, a drug found in over-the-counter eye care products that can cause serious illness if ingested.
Police first started investigating the case in March, when two-year-old Decklyn Desrochers, who was under the care of the suspect, was taken to a local hospital. He had suspicious symptoms that included abnormal drowsiness, low blood pressure, respiratory difficulty and decreased heart rate.
It was when police investigated that case further that they uncovered another incident in which a child was poisoned with tetrahydrozoline. This incident occurred in July 2010, while Allen was running an unlicensed daycare, police said.
Allen, who police say also uses the name Christine Keilbar, ran the daycare from a home in the Pioneer Park area of Kitchener until 2011, police said.