Simplify the following text for a Grade 7 native English-speaking person.
Original: In the early 20th century , mercury was administered to children yearly as a laxative and dewormer , and it was used in teething powders for infants .
Simplified: In the early 20th century , mercury was given to children once a year as a laxative and dewormer . Teething powders for infants also had it in them .