My daughter is 3yrs old but she easily get sick everytime she is having cold ..pls tell me what should I do

A. hi parent when she has cold keep a bowl of chopped onion near her bed approx three feet far over night don't expose her to winds and dust keep her Hydrated by giving her a spoon of water every hour when she's awake use simply purified water having tds higher than 350 avoid maida items, packaged and processed food