Dreaming of altitudes without feeling vertigo means that the dreamer is courageous and undertakes any given challenge. In other words your unconscious is telling you that you are hard to scare. On the contrary, once on the top, dreaming that you get sick indicates that you are still not prepared to face the issues you have to deal with. To the ones that experience this dream it is advisable to wait a prudent time before beginning any given project.
[1]A warning to avoid an involvement with inferiors which could cause you serious embarrassment, especially if the height affected your breathing.
[2]