I was originally told that when DS1 had his first bout, but all it did was make it worse and made him throw up loads of mucous. We found keeping them in a really warm room helped, but I think it's an individual thing because some Mums I know IRL say that vapourisers work for their kids, others say cold air (as in outside) and others are like us and need warm air. You just need to do what makes her the most comfortable.