Does there need to be an even ratio?

[Plane]

http://www.msnbc.msn.com/id/18138850/wid/11915773?GT1=9303

For now, she recommends that people who want to limit their everyday exposure to potentially harmful chemicals read the labels of the household products they buy. For example, she said, “avoid things that say ’fragrance’ but don’t tell you what it is.”