How can I protect my daughters against the dangers of cosmetics?

Patch testing. One simple way to proceed is patch testing.Place a dab of any product you would consider using on a Bandaid & place it on an inconspicuous area overnight.After 24 hours evaluate the area.If it has not produced irritation/break out it is likely to be safe for her to use.
Educate yourself. There is lots of products out there soliciting customers luring them with unrealistic claims of bringing back youth or maintaing youth.Believe me may of us some times bewildered and can not differentiate the good one from not so good one. Your best bet is to go to reputed plastic surgeon or dermatologist and the aesthetician associated with them to look for safe and proven cosmetics.More you lear.