Two things come to mind. The first is to not look at the marks. Master Lin once said not to feel a persons lumps because that additional sensory information makes it harder to visualize a healthy condition. I assume it the same for seeing anything, as opposed to just having the problem described. This is line with the idea of working on the healthy (unblocked) side of person before working on the blockages themselves.
You are working with messages. Easier to consistently and strong send messages of openness and health when working on already healthy tissue... or what you remember as healthy, as opposed to the ailment you experience directly.
Note, that the above is advice on how to achieve the correct messages more easily. Not that it is not possible to do it if you have experienced it. I suspect that it makes little difference to an experienced master like Chunyi.
The second idea is that for an immune system, I think whole body and would like to make sure that the small universe is open and that adding energy to the lower dan tien is a good idea.
You are perfection,
Iam2