What Causes Vomiting In A Child?

my grandaughter had the top off a bleach bottle this morning and although my daughter believes she didn t drink any, as no evidence seen, she has spat out all food etc today, she has been out with us shopping and happily walked around the shops, my daughter has had a vomitting virus last thurday and grandad has vomitting virus today and now my 2yr old grand-daughter is vomitting. should we be concerned ?